PESCADERO MARSH CONTRACT REPORT

DEPT. PARKS AND REC. CO!\lTRACT #

4-823-4010 U.C. SANTA CRUZ

DR. ROBERT R. CURRY COPY 2

State of California

DEPARTMENT OF PARKS AND RECREATim:r-

Natural Resources Division

1416 9th Street, Room 923 Sacramento. CA 95814 PO. Box 942896, Sacramento, CA 94296-0001

(916) 653-6725 FAX (916) 657-3335

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STATE OF CALIFORNIA

INTERAGENCY AGREEMENT STD 13 (REV. 9-81}

THIS AGREEMENT is entered into this 11th day of April , 19 ..§i, .JY and between the undersigned State Agencies:

Set forth services, materials, or equipment to be furnished, or work to be performed, and by whom, time for performance including the terms, date of commencement and date of completion, and provision for payment per (1212.1-1212.2 and 8760-8760.2 SAM.)

Distribution:

Agency providing services Agency receiving services Department of General Services

(unless exempt from DGS approval: Controller

The Regents of the University of California, Santa Cruz, hereafter referred to as UCSC, agree~

to provide the Department of Parks and Recreation, hereafter referred to as DPR, with all labor, materials, tools and equipment necessary to perform a hydrologic and monitoring study of Pescadero Marsh, San Mateo County, California. Work shall be performed in accordance with proposal narrative, Exhibit "A", which is hereby attached and herewith made a part of this agreement.

Dr. Robert R. Curry is the Principal Investigator for this projec't. UCSC agrees to commence work immediately upon approval of this agreement and to complete Phase II by December 15, 198• DPR agrees to pay UCSC upon receipt of invoices in triplicate showing the time period covered and the work items accomplished. UCSC shall send invoices to the Department of Parks and Recreation, Resource Protection Division, P.O. Box 2390, Sacramento, CA 95811, Attn: Natura: Heritage Section.

The total amount payable under this agreement shall not exceed TWENTY THOUSAND DOLLARS AND NO CENTS ($20,000) including all applicable taxes computed in accordance with Section 8760 of the State Administrative Manual. Nothing herein contained shall preclude advance payments pursuant to Article l, Chapter 3, Part l, Division 3, Title 2, Government Code.

For the purposes of this agreement with the University of California the direct and indirect costs as a percent of the direct cost, allowable for payment, shall be as identified in this agreement and are not subject to retroactive disallowance pursuant to Government Code Section 11256.

Unless specifically exempted in Exhibit "A" any tools or equipment (nonexpendable items) pur-~-t.. __ ,_ .. ., r- .....................

NAME OF STATE AGENCY ~ 'N'A"Nff:f OFSTATE AGENCY

De~rtment of Parks and Recre~~ion The Regents of the University of California, CALLED ABOVE (SHORT NAME) CALLED ABOVE (SHORT NAME) Santa. Cru:

DPR ucsc AUTHORIZED SIGNATURE AUTHORIZED SIGNATURE

~---------------------------------------------------~~~~~~----------------------------------------------TITLE Valente F. Dolcini, Manager TITLE

Business & Fisc~a~l~s~e~c~t~i~o~n~----------------i~================================================= PROGRAM/CATEGORY (CODE AND TITLE)

(Continued on sheets which are hereby attached and made a part hereof) General DEPARTMENT OF GENERAL SERVICES AMOUNT ENCUMBERED - 'J=u::::.N_:::D:_:,:..:TI~T::..:L:::.E=-.------------------·---- -------------

USE ONLY $ 20.&00 ---------~-~S~ort ·····-----·--------·------------·-UNENCUMBERED BALANCE (OPTIONAL USE)

~'-OJ_. _'N_C-~RE~A~S-._N_G_-.~N~C-U~· .. -BR-A--NC-E--·--·--~--~T-E-;-7-9-0-_-0-0-1-_-0-0-1------J;;;;:; 1

~~A;~T-E _r;;A8L~;~ ADJ. DECREASING ENCUMBRANCE OBJECT OF EXPENDITURE (CODE AND TITLE)

f_L _____ _ 04-84 823-401 @_~-~~~~~~-~~~==~ T.B.A. NUMBER B. R. NUMBER

I He·reby Certify upon my own personal knowledge that budgeted funds are available for this encumbrance.

SIGNA7T=u:7R~E~-~O~F~A~C~C~O~U~N~T--IN __ G __ O_F_F_I_C_E_R ____________________ -4-D-A._T_E _________ ~------------

~_e.ll> ________________________________ ·-·------·-------------

I hereby Cet1ify that all conditions for exemption set forth in Stale Administrative Manual Section 1209 have been complied with

and this document Dis exempt Dis not exempt from review by the Department of Finance.

-=====-===·:·= ============:'::-I:::G::::N=A=T::::U::::RE: ~FFICER SIGNING Ot~ BEH~LF 0: AGENCY ·=r-A-.-rE---.. -------~---

HYDROLOGIC STUDY ~· PESClillEfR) MARSH ·~ PHASE II

Proposal ~m: Cooperative Agreement rx::tween the;

California Deparb:nent of Parks and Hecreation

and the

University of California Santa Cruz

!"'larch 14 v 1984

-"-~by }~obe:rt R. Curry, College Eight 1 Univ" California u Santa Cruz, 95064

phone~ 408 429-4061 or -·290vJ

I. OBJECTIVES:

Establishment of a sound rnanagernent plan for Pescadero Marsh and Lagoon

requires information not presently knovm" This".; includes primarily study of the

budget of sediment and vJatc:r that annually flows into and out o:E the

lagoon/marsh complex q and estimation of the oppo1:tuni tic:o:s for manage-ment of

both sediment and water flow. 'l'he Phase I study has 1:evealf:'d tha'cy in its

present state, the influx of sediment into the m;:_u::sh area is so bi9h that

flushing by tidal arxJ/or storm action not possible. Given

without control of sediment sources and/or: management. of the m.i'l:rsh/1agoon sys-­

tEm for optimal sediment flushing, :Eurthe1: degradat.ion of the syst..;::-;m and less

of \vildli:Ee habitat v.rill ensue.

Sediment sources identified in the Phase I study are outside of areas

under statE2 management control. Opportunities exist for tive work with

landowners to reduce sediment flux. Hm,Jever u preliminary findings

so much sediment is stored in channels above the rnarshv pm:ticula:rly in the

Butano Creek Hat:ershed, that control of a rnajority of the sedim<::nt through

that

cooperative programs with landov.,>ns:rs \vould be c~normous1y cUff t and c-r.Jstly.

Phase II Study "' Pescadero l'larsh 1\1ar. 14 8 1984

P:rel iminary \vorl\: in Phase I .suggests that a management: p:roq:ran1 dir-ected simul­

taneously at both re-duction of source sediment and improvernent of the natural u

sustainable flushing capability of the rnarsh/lagoon system may be most cost

effective and provide maximL'ln opportunities for wildlife hDbit.at cnbam::ernPnt.

To establish a sound rnarsh and lagoon management plan vvill H2C]<JHC~ a sedi~

rneot .and vJater monitoring program through a full winter flow season. The data

thus derived vJill then be 11 nonnalized 11 to establish estimates of runoff and

sediment flux in 11 averagei! years and in a series of years of record of past

flows. This permits use of a single years 9 data to modc:"l statistically

expectable future flow reg .imes o

The hydrologic monitor inq program being pr:oposc:d in this phase of study

1.vas anticipated in the fit·st Phase l study 9 now cornpletec'l. In that initial

phase of workv streamflow and sec1iment monitoring stations vJe1:e established at

the Highway l bridge at the outlet of the system to the sea f and on th<.:; pdnci­

pal inlet streams of Butano Creek at it crossing by Pescadero Rd (Co., Rc.'L 35) f

and at Pescadero Creek at the crossing of the same road. Additional sedirnent·-­

onl y rnoni tor ing stations vJi 11 L>e on l3utano Creek at Cloverdale Road u to mord tor

influx of sc">dirnent to the 11Willow rrhicket" sediment storage area above the

marsh sampling site u and at the mouth of Little Butano Creek on a bridge near

the westernmost boundary of Butano State Pa:cku to monitor sediment fo:c a rela·c~

tively little disturbed subwatershed of the troublesome Butano drainage basin,,

l\ • OBJ rx::'I'I VES :

l. Develop tbe hydrolo(J ic and sed imentoloq ic input nccessa:ry to 2ssess the

proposed Pescadero l'1arsh restoration and manaq(:;rnent plcH!s and recomnend

modifications to better accomplish the restoration objectives.

Phase II Study - Pescadero t'iarsh l'lar. 14, 1984 Page -2-

2. Prep:.;n:e a hydrologic assessment report basc~d upon regional field

studies by July 30, 1984. 'l'his report is to address all thm:c;(,; questions in

the l\ugust 1 1979, Task Objective repm:t by Jack Biehle-: that can be ansvJer.ed

with one year 1 s field data base in addition to existing historical info:r~ma.,.

tion. This report vlill additionally assess historic changes sediment

fluxes carried to the tvlarsh by Butano and Pescadero Creeks and lonqshon:

marine processesv and will attempt to pr·oject chan9es in sediment flmt that

may be expected in the future bast:od upon data available th:Y:<Ju9h the 1984

water--year.

B. TASKS~

1). Evaluatt:! all historic data 1 including available 5vJ."·ye.'J.r aer photo

x:ecord and historic maps for evidences of paGt dynamics of this coastal

marsh system including dune act:ivityv delta developn<::ntr channel dmngesu

veget.ati<)n status, beach bay--mouth b-ar dev<:~lopr1ent f ancl c-:rosicmal status of

state lands su:o:ounding the marsh and of lands w:i thin the

of Butano and Pescader·o creeks.

2}. Conduct studies of sediment cm:es and available drill

cadero r1arsh f:;edirnents v supplemented with m~vJ coring ~,.,h,~:rr2

determine trlli.'= histor: ic flux of sediment into and out of tb

last few hundred y~ars.

te

monitoring to

of Pes~

to

3) • Condoct additional se<Hment and v.Jater

full-·year. approximations of sediment fluxr. inity variation, vJa.b:!r

variation? beach dyn,:unics, and local gully se:'dirnent production.

4)" Evaluate the full range of existing and nE!W proposE:''C1 options

Phase r r Study - Pescadero IV:arsh i'1ar < 14 F 1984

including 1 but not limitsx'l tor redesign of Highvvay l bridger const:cuction

and operation of Butano Cre-ek secErnent tJ.:appint] pr .. :mds, reconstruction of

Pescadero Creek channel just east of the present Stat(:: Park lands to that

more stable course that was changed bett·;een 1927 and 1939 Q trade of 1arK1s

bet\veen the State and adjacent private property ov.illers to tigate effects

of flooding on the lower Campinotti property, possible operation of tl1e

"vJillow thicket" area as a sedirnent stora9e trap along Butano Creek~ and

others options that include changes in present diking patterns.

III. TIMING:

Ideally, sediment and flow monitoring should have been implemented by the

beg inning of runoff in the fa.ll of 1983. •rhe fre<:?ze on renewals of state con-­

tracts for 1983 necessitated approximately 25 volunteer fh:!ld visits to the

site to collect spot discharg(c'? and sediment data" Some reconstn1ction of ec;u:ly

flow records is necessary and feasible based upon the observations of staqe

made in the Phase I study. \;vork had to begin ~:;fore funding approval to estab-·

lish a salinity record and flow record for the cJ:::itical fall and vvinter pcd.cxL

Flow and sediment data must be collected throu9b July, to match with dat .. a col-·

lected this past sunmer under Phase I. Due to the atypical and non-­

representative nature of the precipitation and runoff for January and February

of J.9f:l4 v (an aU-time :record low precipitation for that two--month period) v nor-·

malization of the collected data will require siqnificant stati~tical zmalysis~

This \vill t.e accomplished using all hydrologic data available fm: the Santa

Cruz Mountain area for the full pel.: iod of recon1 r as developed and maintained

by the UoS. Geological Surveyu ~vater l~esources Division. Coor--Y:::rative computer

analysis of their data-·base is anticir_::.;:.1ted to con1pdsc:: a major contribution of

th2 P. I" A cc--mpletion rerxnt can be drafted by July 30 base-d upon projected

Phase II Study - Pescadero Marsh l"lar. 14, 1984

flow and sediment concli tions and a final ve:ri d;:aft \'\fill b:,? availabh~ by

September 30q 1984,

IV. BUDGET~

Primary managernent guidelines and opportunities vJill be provide""'] by the

Principal 1nvesti9ator wi tbout any :cemuneJ:ation. Data \•Jill J:x; collected unde:r

the supc::rvision and direction of the PoL using students at the:? Urliversi ty of

California in vJatersheJ I·1anagement and Ecosystem Restoration studies 0 and \vi th

the assistancev vmere feasiblep of State Parks personneL It is anticipated

that some C:--qui;cment will be ma.de availablE:" through state r·esources or coopera~"

tively t.hrough loans from state agencies. Strec:tln flovJ gauqing equipment to be

or:erated from a bridge crarH~ is the single most exrensive and difficult to bor-·

row item. If this unusually dry ~.<linter runoff pattern contmues 1 bridge·,crane

work will not be neoassary. All mE~asurr:cnK?nts \;Jill be~ possible using hand·~hf31p

pygmy~ type and long-pole lovi-·Veloci ty cur :rent meters~ S<-~iment sampling equip--

ment is available through the Oni versi ty of California and th:cough equiprnent

O\vt1ed by State Parks.

Primary budget i b:oms 2.re hourly r:eimbursment fo:c part of the \.vo:rk by stu-

dents, some e<:ru.i:t;mentu computer analysis~ and p.:"r diem for

tographye surveying equiprrt2ntu SL3ff gaug<:-)Sv and initial field v1ork throughout

the \vatershed vJE:re accompli shoo under Phase I. l:\.ddi tional analysis of the I

aedal photographs of the watershed and of the lagood to develop a history of

chc:mge in land use and lagoon form and 11 ise one:: of major

student efforts" Other student-~aidcd v;ork 11 :include detaU.ed wa tex: surface

profiling, sediment and \·Jater floVJ sarnplir<g t bda1 flux ::;ynoptic flovJ vo1urne

measure11ents in the estuaryv and hand codnq of lagoon floor sedirnents through

Phase II Study -- Pescadero r1arsh i"lar, lA, 1984

skin-diving.

L

BUDGET

Hourly student help calculated at 36 hours/week for 24 weeks at an average of $8/hr Hourlv student E..'<Jitorial vlorku 50--hrs at $10;1w Employee benefits @ average 1% of hourly \.vage

$6912 500

74

II. Contract Services:

Computer Time (UCSC) 200 Computer Time (USGS - system) l"lenlo Park & Washinc;~ton 300

III. Supplies and Ec!uipnent

Permanent equipment - (to become property of State Department of Parks and Recreation) •

Salinity-conductivity meter with probe and cable" Yellmv-Spdngs S·-c-T rlbdel 33 600 Hand core sampler and tubes 285 Dissolved Oxygen meter with 50-ft cable: Yellovr--Springs fvbdel 57 1400

Permanent equipnent - compatible Vvi th UCSC~owned equipnent.

Used floppy-disc based microcomputer :for teler::-·hone access to remote data files and USGS sofb·Jare to dovmload to Unix VAX 750 at UC..'SC (recommended old Osborne or KayPro) JA50

Low velocity long-pole extension current. meter for tidal estuary use -· Swoffer IViodel 21 00-L, to cornbi ne with UCSC Pyqmy 1550

Expendable equiprnent:

2 pr wadersv fins, face-mask 2 pocket thermometers F'luorescene dye t.Elbs Mise. sample bags and brJttles Replacemer1t seives (2)

IV. Other Services

Copy services, postage, printing, telephone Drafting supplies and services

V. Travel and Per--Diem

190 12 41 40

120

150 120

mileage to the site: 30 round-trips of 80 mi @ $0. 21/mi 504 mileage within the wate~::·shed: 400 @ $0. 21/mi 84 in--field per~diem @$9. 00/day x 60 days ::>40

SUBTOTAL Direct EX[..:>enses 15072

Overhead ·- offcampJs @27. 2% of Direct 4100

TOTAL: $19172

·1 / th 1 <; 8 i nnd bct1J/c;t:;n the under:)!9ned Stoh.~ /~\qencie·~:

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Plate 1: Aerial photo~jraph taken in 1928 or 1929, probably in Septe;nber, CX:;toi:::Er or November, 1928. Original photonrontage in San Mateo County Planning files, Ocean Shore Eailroad. North is up in photo.

Plate 2: Pescadero Beach and lagoon mouth area, 9:28 AM, 11-5-83, showing beach overwash, overwash delta formation and back-beach water flow to the south, toward the observ~r. Lagoon stage is 4.80 rnsl with no return flow to sea. Photo by R.R. Curry.

Plate 3: Pescadero Beach and lagoon mouth area, 10:10 AM, 11-5-83, showing rapid development of south-flowing back­beach water and sediment transport channel forming delta in lagoon mouth. View south. Lagoon stage 4.80, closed. Photo by R.R. Curry.

... Plate 4: North Abutment, Highway One bridge, lagoon in background . Bar open, stage 1.41, 5-18-84, ·11 :00 AM, view SE. Photo by R.R. Curry.

,,

Pl ate 5: View of Pescadero Creek outlet channel at thP site of 11 bid bend., approximately 300 ft downstream fran Highway One bridge. Rocks in foreground, channel center are elevation +0.76 ft rnsl, stage in estuary is 3.92 ft msl on falling tide at 9:30 A~, 11-15-83. Overwash delta formed in previous two weeks visible at left from bridge to foreground. Bar is open. Photo by R.R. Curry.

Figure 1: 1854 topographic map of Pescaclern Marsh arect. U.s. Ctxmt Survey, Register 682, Section X, Map of a Park of the Coast of California, original at a scale of 1:10,000, surveyed by W.l1. Jol1nson, contour interval 20 ft. This figure reproduces a portion of the sheet titled "Punta del Bolsa northward to 'l'unitas Creek" .

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Pescadero Marsh Management

A Plan for Persistence and Productivity

Robert Curry, Robert Houghton, Tom Kidwell, and Philip Tang

--University of California, Santa Cruz

January 28, 1985

~ OF ILLUSTRATIONS

Plate 1. Aerial photograph taken in 1928 or 1929, probably in September,

October or November, 1928. Original photomontage in San Mateo

County Planning files, Ocean Short Railroad. North is up in

photo.

Plate 2. Pescadero Beach and lagoon mouth area, 9:28 AM, 11-5-83, show-

ing beach overwash, overwash delta formation, and back-beach

water flow to the south, toward the observer. Lagoon stage is

4.80 msl with no return flow to sea. Curry photo.

Plate 3. Pescadero Beach and lagoon mouth area, 10:10 AM, 11-5-83, show-

ing rapid development of south-flowing back-beach water and

sediment transport channel forming delta in lagoon mouth. View

south. Lagoon stage 4.80, closed. Curry photo.

Plate 4. North Abutment, Highway One bridge, lagoon in background. Bar

open, stage 1.41, 5-18-84, 11 AM, view SE, curry photo.

Draft Page 1

Plate 5.

Figure l.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

View of Pescadero estuary outlet channel at the site of "big

bend" approximately 300 ft downstream from Highway One Bridge.

Ricks in foreground, channel center, are elevation +0.76 ft

msl, stage in estuary is 3.92 ft msl on falling tide at 9:30AM

11-15-83. overwash delta formed in previous two weeks visible

at left from bridge to foreground. Bar is open, curry photo.

1854 topographic map of Pescadero Marsh area. u.s. Coast Sur­

vey, Register 682, section X, Map of a Park of the Coast of

California, original at a scale of 1:10,000, surveyed by w. M.

Johnson, contour interval 20 ft. This figure reproduces a por­

tion of the sheet titled "Punta del Bolsa northward to Tunitas

Creek."

Pescadero Creek watershed, showing both permanent (solid line)

and ephemeral waterways.

Pescadero Marsh base map, showing named marsh subareas and the

State Preserve boundary. Contour interval 100 ft.

Pescadero Marsh today, showing (cross-hachures) areas of marsh

vegetation depicted in the 1854 map.

Pescadero Marsh area showing principal dikes.

Pescadero Marsh showing progressive growth of agricultural use

of marsh lands, based upon aerial photographs at the indicated

dates. Angle of hachure corresponds to date in legend.

Pescadero Creek watershed showing history of 20th century log-

ging. Hachure pattern and angle correspond to decade-dates

Draft Page 2

indicated in legend.

Figure 8, Pescadero Creek watershed showing publically owned lands in

relationship to the Marsh Preserve.

!· Introduction

Located in the coastal mountain fog belt of central California 35 miles

south of San Francisco, the Pescadero creek basin is at the fringe of the com-

muter range, but has long been an objective for weekend and vacation visits by

californians. This 81 square-mile watershed is the largest of the coastal

basins of the san Francisco Peninsula, north of santa cruz county. From about

river mile 3 (measured upstream from the ocean), Pescadero Creek meanders

through a floodplain of geologically recent origin. The major axis of Pes-

cadero creek has a straight-line length of about 13 miles and a watershed «L

width of about 3 miles. The principl~ tributary of Pescadero Creek is Butane -'(

Creek, which has a drainage area of 21.2 square miles. The upper reaches of

Pescadero Creek and its tributaries are incised into bedrock in deep v-shaped

canyons. The region is characterized by its centuries old stands of redwoods,

generations of artichoke farms, and by one of the more popular 'birding' areas

in the Bay Area which happens to be one of the most productive type of ecosys-

terns known.

At the mouth of Pescadero watershed within the coastal santa cruz Moun-

tains, Pescadero Marsh is one of the most significant coastal wetlands between

the San Francisco and Monterey Bay areas. The Marsh is an approximately 320-

acre brackish and freshwater wetland found at and about the confluence of Pes-

cadero and Butane Creeks.

Draft Page 3

The lateral extent of the marsh is determined by the historical flood

plains of the Pescadero and Butane creeks, agricultural cultivation, coastal

dune(beach formations, and an artificial levee system including roads. Sur­

rounding land-uses include: agriculture and livestock grazing, residences and

businesses, conservation and recreation, and timber harvesting. Recent

acquisitions by the Department of Parks and Recreation have included nearly

all of the historical marsh area.

l·l· Problem Statement

Pescadero Marsh is the focus of concern for a diverse and frequently con­

flicting amalgam of interest groups. Essentially, sediment and water are the

crux of a problem affecting conservation groups, 'birders', farmers, townspeo­

ple, and state and local agencies. Each group is differentially affected by

an accelerated rate of natural processes responsible for the progressive

diminution and degradation of this unique coastal wetland habitat. The

accelerated rate of natural processes is attributed to land use patterns and

practices operating within the watershed, as well as large-magnitude climatic

events. Prevailing conditions threaten the productivity and persistence of

the estuarine portions of Pescadero Marsh. Excessive sedimentation and low­

land development have progressively reduced water storage capacity of the

marsh, thereby increasing the flood risk to both town and farm, while burying

unique wetland habitat and shortening the life expectancy of this marshland.

Poor circulation, turbidity, and contamination limit primary productivity,

ultimately affecting fisheries and birds. Concern over the marsh has been

expressed by the aforementioned diverse and frequently conflicting interest

groups, each of whose solutions become the problems of the others.

Draft Page 4

As defined in this report, the basic problem is easy to state: How can

the marsh unit, owned by the state of California, be managed so as to maximize

and prolong natural coastal estuarine-marsh function, productivity, and

longevity? The natural consequences of decline in rates of rise of world sea

level coupled with ordinary transport of sediment by streams feeding

estuaries, is a filling of those features. At Pescadero, we have the added

natural problems of high rates of geologic uplift of coastal regions and high

rates of \~'¢if>~~c erosion from poorly consolidated highly faulted mountainous

watersheds. We also must face, at Pescadero, the activities of humans who, in

the past, have been supported by government and economic policies directed

specifically at the acceleration of the natural processes of infilling of coa­

stal marshlands under the rubric of "reclamation." Our real problem at this

site today becomes, then, the development of a management plan that is sensi­

tive to a balance between progressive natural processes, historical human

uses, and perceived wildland values.

The problems of Pescadero Marsh result from a complex set of environmen­

tal processes, land-use patterns and practices, and diverse and sometimes con­

flicting interests. The cumulative effects of actions and events occurring

throughout the watershed are problems which cannot be solved in isolation. A

management program intending to effectively and efficiently handle the

resources of the marsh must address the watershed in its entirety, rather than

operate from the premise that the marsh functions independently of its sur­

roundings.

For management purposes, the watershed has been conceptually subdivided

in three primary subunits characterized by their distinct habitats. Though

not separate, the distinctive character of each subunit manifests the particu-

Draft Page 5

lar set of processes dominating that locale and demanding a unique management

approach. These primary subunits are: beach zone, marsh zone, and the upper

watershed. In terms of water and sediment budgets, each subunit corresponds

to the areas of discharge, storage and input, respectively. For each subunit

goals and objectives are defined, natural processes described, and recommenda­

tions derived from the integration of objectives and processes.

section 2 of this report introduces the Pescadero Marsh as a valuable

resource, establishes the need for concerted management and states the goals

and objectives of of such management. Part 3 outlines briefly the methodology

employed in ascertaining processes and the consequent formulation of a manage­

ment plan. Part 4 audits the results of that methodology, while Part 5

integrates information and intent with a discussion of ongoing processes,

including an analysis of the effects of those processes upon desired manage-

ment goals. Part 6 concludes with a delineation of recommendations for

management for persistence and productivity of the Pescadero coastal wetlands.

1.2. scope of Work

The purpose of this document is to set forth a priority of recommended

actions to be undertaken by State Parks and Recreation to insure the per­

sistence of the Pescadero Marsh system as a valuable natural resource. Prere­

quisite to the fulfillment of this goal is the definition of objectives and an

understanding of the processes which significantly affect the longevity and

productivity of the Pescadero Marsh. Initial resource inventories and the

justification for more concerted management of the Pescadero Marsh preceded

this document. Although critical to the methodological development of a

management program, they will not be the focus of this work. While fully cog-

Draft Page 6

nizant of the limits of state Parks and Recreations' jurisdiction, this

management plan addresses issues encompassing the entire watershed which sig-

nificantly and directly affect the functioning of the coastal wetlands region,

in accordance with the statement of the problem. Although contracted by state

Parks and Recreation and designed primarily as a basis for management deci-

sions, this plan also provides guidance to other parties interested in the

persistence and productivity of the Pescadero coastal wetlands area.

~· ~ for Concerted Management

As expressed previously by Elliot (1975) and Violis(l979), the Pescadero

Marsh has a pressing need for more concerted management which is justified by:

(l) its unique ecological value as a coastal wetland,

(2) its fish and wildlife values,

(3) the accelerated rate of natural processes adversely affecting those

values,

(4) external stresses which persistently threaten the existence of the marsh

as a natural resource,

(5) and the panoply of diverse and frequently conflicting interests and

land-uses operating at and about the marsh.

Given the marsh's location at the mouth of the Pescadero creek watershed,

it is subjected to the cumulative effects of actions and events occurring his-

torically throughout the watershed. Those resources affected include:

l. safety (in regards to flooding risks) 2. economic and residential development 3. agricultural land development and "drainage"

Draft Page 7

4. fisheries 5. marshland habitat 6. wildlife and rookeries 7. recreation

The diverse and frequently conflicting resource uses that cumulatively

generate those impacts include:

1. flood control a. diking b. channel alteration c. sand bar breaching

2. habitat maintenance, restoration and enhancement 3. fisheries and fishing 4. agriculture 5. silviculture 6. economic development 7. residential development 8. recreation 9. interpretation and education 10. roads and bridges (including Highway one) 11. waste disposal

a. septic tanks b. landfills

12. water supply a. diversions b. impoundments

13. other land uses a. quarrying b. off-road vehicles

The particular resource-related concerns arising from this set of uses

include:

1. flooding a. town of Pescadero b. roads c. cultivated lands

2. productivity a. agricultural b. marshland ecosystem - primary productivity

3. habitat loss 4. fisheries 5. water quality

a. salt-water intrusion or lack of intrusion b. chemical contamination (agricultural, landfill, and

roadway runoff and/or leaching) c. turbidity

Draft Page a

d. BOD 6. erosion and sedimentation 7. circulation changes 8. invasion of exotic species

~·1· ~-induced Environmental Change

Types of environmental changes affecting the Pescadero Marsh caused by

human intrusion:

l. reshaping of coastal water drainage by channelization and dredging, diking, and filling,

4. restriction/reduction of tidal flows by roads, a rail­road crossing, dikes, channels and other structures in the wetlands,

s. disruption of water circulation by' same, 6, reduction/restriction of stream flows into wetlands by

diversions and detentions, 7. altered runoff patterns with increased flood peaks and

reduced infiltration, 8. accelerated sedimentation, 9. water pollution by point and non-point sources,

10. vegetation and soil disturbance due to excessive human use of wetland,

ll. degradation or loss of supporting upland vegetation, 12. invasion by exotic species.

~·~· Management Principles for Pescadero Marsh

Certain conditions constrain the formulation of a management program for

the Pescadero Marsh which include:

(1) a significant time limitation due to pragmatic concerns;

(2) incomplete knowledge of processes affecting the marsh due to the absence

of sufficient preceding study, limited resources, and the above mentioned

time constraint all result in extensive uncertainty;

(3) and the fact that the Pescadero Marsh is a critical and sensitive habi-

tat.

Draft Page 9

Given such constraints, management of the Pescadero Marsh should:

(1) be designed with an experimental methodology,

(2) minimize the potential of adverse effects while optimizing system bene­

fits and improving understanding,

(3) proceed cautiously and incrementally, allowing sufficient time for the

system to respond to modifications.

~·l· Unique ~ of ~ Pescadero ~

The unique value of coastal wetlands as a natural resource is well esta­

blished scientifically, and institutionalized in the california coastal Act or

1976, stating that coastal wetlands are by their nature a vital interchange

between the land and the sea, a critical link within the food chain, and one

of the most productive living systems known, the coastal Act establishes poli­

cies and priority for their preservation, enhancement, and restoration. Addi­

tionally, Pescadero Marsh has been identified by the state as a top-priority

wetland due to its fish and wildlife values and due to the persisting threats

to its existence as a natural resource. Little else need be said of these

values except where their preservation conflicts with other land-uses and

interests. This is the case in Pescadero where the preservation of wetlands

displaces prime agricultural lands and vice versa.

Agricultural concerns are critical to the state, the county, and to the

community. However, each jurisdiction has established policies to suit its

own provincial interests which at times contradict the interests of others

(i.e. the state guides agricultural development from coastal areas to the cen­

tral valleys, while san Mateo County has placed the marsh in an agricultural

Draft Page 10

district). Despite the intent of regional interests, they can not be legitl-

mately instituted at the sole expense of local interests. Farming and ranch­

ing have been the way of life in Pescadero for literally hundreds of years,

and these local and historical interests must be factored into any plan. A

balance must be found between local and regional interests. To the extent

that regional interests cannot dictate land-use policy in the watershed as a

whole, the success of any program is dependent upon and can be judged by its

local reception.

~·1· Uniqueness of ~ Project

Few more than a score of coastal wetland restoration/enhancement projects

have been completed in California (Josselyn, 1982). And less than a handful

of those approach the size and complexity of this project, wetland restora-

tion is presently "more art than science." certainly, the science of wetland

restoration and enhancement is young and is based on a haphazard experience of

success and failure (Josselyn, 1982). In a review of past wetland restoration

projects in california, two major weaknesses in the planning process were

described: first, the objectives of a project are usually very general and not

stated clearly in the planning documents; second, project monitoring should be

included in the planning stage so that funds and personnel can be dedicated to

evaluating the success of the project. Restoring a major ecosystem is not a

simple task, but requires careful observation once construction is completed

and tidal action restored. To the extent that monitoring can enhance our

present understanding and improve future projects, greater effort should be

directed toward it, and the public can be assured that its money is well

spent.

Draft Page 1.1

Given this lack of precedence, the difficulty of establishing a func-

tional methodology and a definitive set of goals and objectives is exceeded

only by their necessity.

~· Methodology

General methods applicable to a study such as this are straightforward.

For development of a management plan, rather than simply study leading to the

development of such a plan, an interactive, semi-empirical review process must

be added to those necessary for study of background needs. In outline, these

include the following:

I. Define coastal wetland planning and management area. II. Establish goals, objectives and priorities by ass­

essing local interests and state-wide and reg­ional analyses of wetland resources.

III. Conduct resource inventories and establish base­line data.

IV. Postulate historical evolution of the wetland, establishing historical and present extent and condition of wetland.

v. Characterize and define degree of degradation, extrapolating future of marsh under continuing conditions assigning factors of responsibility - internal and external stresses.

VI. catalogue land ownership, and assess land-use practices and patterns affecting the state of the marsh.

VII. Propose a range of management alternatives. VIII. Predict results of various management proposals.

IX. Public review and comment. x. Revisions.

XI. Implementation. XII. Establish monitoring program.

XIII. Evaluation.

!· Goals and Objectives for Pescadero Marsh Management

A set of goals and objectives must be defined for the effective and effi-

cient guidance of the project, as well as for the establishment of a standard

Draft Page 12

by which to judge progress. Moreover, the development of criteria by which to

formulate and validate the definition of said management goals is a prere­

quisite to further work.

1·1· Establishing Management Goals ~ Objectives

To manage this area as a marsh implies restoration and in turn most sim­

ply suggests returning the area to its pre-disturbance state. However,

knowledge of the prior pristine and natural conditions upon which to model

such a restoration does not exist. Nor would its re-creation be necessarily

possible or desirable, even if its prior state where determinable. As a result

of dramatic and irreversible changes within the entire ecosystem such restora­

tion of pre-disturbance conditions is precluded. First, since the character

of the marsh is inextricably linked with its watershed, marsh restoration

becomes synonymous with watershed restoration as well--clearly an impractical,

if not impossible requirement. second, the marsh is a naturally dynamic com­

munity, continually changing in response to sedimentation, flooding, rising

sea level, and other coastal processes. on a geologic time-scale its

existence is short, and it would be difficult and arbitrary to recreate a sin­

gle stage in its development.

For what then, should a marsh restoration project strive?

The stated desire to restore Pescadero Marsh presumes a set of values associ­

ated with the marsh, each defined as some characteristic of recognized util­

ity. Since these values are of demonstrable importance and justify a manage­

ment program, it is logical that they should determine the design of a res­

toration project.

Draft Page 13

The first accurate and detailed map of the marsh-lagoon system was pub-­

lished by the u.s. coast Survey in 1854. It was based upon surveys immedi­

ately following statehood in 1850, and was published at a scale of 1:10,000.

The portion of this map covering the Department of Parks and Recreation's

lands is shown in Figure 1. The map was revised based upon field surveys made

December 27, 1895, but no changes are shown in the location of natural wetland

boundaries. These early topographic maps of the Coast and Geodetic survey

were made with certain conventions for the depiction of wetlands. The maps

clearly show open water and seasonally flooded wetlands. The boundaries shown

as wetlands in the 1850's through 1890's comprise those boundaries of areas

subject to frequent seasonal flooding today. These are the areas subject to

regular salt-water flooding on a seasonal or every-other-year basis. They

generally lie at elevations today of 4-6 feet above mean sea level to mean sea

level. Pescadero Creek itself is shown as either diked or flanked with

natural levees, upon which a road and trail system is indicated.

The 1854 map, and the cultural revision of December, 1895, comprise an

extremely valuable historic resource. The scientific interpretation of this

coastal topographic map series has been the subject of intensive research by

Joal Bergquist of the u.s. Geological Survey (1978). Bergquist used this map

series to assess historic changes in Bolinas Lagoon. He found that they were

made with planetable and alidade, with distances measured by chaining. For

the Pescadero maps, some of the equidistant chain stations and alidade sta­

tions are noted directly on the map, so it is possible to determine the rela­

tive accuracy of the intervening areas that were "sketched-in." By and large,

the map is very accurate, since it was based upon a geodetic network and done

by careful surveyors.

Draft Page 14

At Pescadero, the planetable was set up along the shore and through

uplands around the marsh at intervals of 1200 to 1600 feet. The rodman then

walked the shoreline, and walked into the marsh, stopping at suitable inter­

vals for sighting by the topographer and for measurement by the chainmen. The

boundary between land and water is delineated as the line of mean high water

( MHW)( Shalowitz, 1964). In practice, this was the line of drift-wood and

debris left by the preceding high waters. Since there are two high tides of

different elevations on the west coast, official instructions to topographers

were to draw the line somewhere between them. In practice, however, it is the

higher high-water line that is preserved around the lagoon and on its beach,

so probably that is what was sketched as a stippled beach deposit in Figure 1.

The horizontal hachuring that indicates marsh-lands was depicted based upon

"marsh vegetation." In practice, these comprise the areas that are seasonally

flooded, and do not include those subject to flooding at less frequent inter­

vals. At Pescadero, the dominant "marsh" vegetation is found in areas subject

to salt-water flooding at frequent enough intervals to limit vegetation to

salt-tolerant species. Thus, it is no surprise to find today that salt­

affected soils are almost exactly delimited by the boundaries of the marsh­

pattern on the 1854 map.

The 1654 map provides a graphic representation of areas where soils and

elevations today are conducive to marsh restoration. In other words, the

areas shown as seasonally flooded ~etland vegetation lands in 1854 comprise

areas where the potential exists for restoration to those conditions today.

Another valuable resource for establishing management goals is a

vertical aerial photograph. This remarkable document (Plate 1) was taken for

the contemplated ocean Shore Railroad along the california coast through san

Draft Page 15

Mateo County. After several years of search for the photos, a single copy was

found and is reproduced for this report. This photo provides a baseline

record of the exact character of the marsh and surrounding area. Although

much human activity is evident, the outlines of the "potential wetland" are

still clearly visible and are remarkably consistent with those of the 1854

map. This photo thus provides yet another defensible and sound guide to res-

toration of marsh habitats.

Given the regard for ecological uniqueness of the Pescadero Marsh and the

associated biological and cultural values including'education and recreation,

wildlife and fisheries habitat, and its unsur)?assed potential for primary pro­

ductivity; any management of the marsh should be guided by the preservation, \

enhancement, and restoration of these values, balanced against concerns aris-

ing from such land-use practice including flood protection and agricultural

productivity. In essence, the criteria defining management goals are those

values and concerns which initiate and justify more concerted management.

Accordingly, a fundamental management goal for the Pescadero Marsh could

be stated as:

to develop and maintain the optimal utilization of state lands as a unique

and vital ecological habitat, conjointly' with surrounding private land '

uses, in an effective and efficient manner.

1 The original photo is part of a set of hand-held unannotated original prints bound in an unmarked volume in the san Mateo county Planning Depart­ment. They were found by the Environmental Planning staff after diligent search. The photo is undated but, based upon conditions shown in santa Cruz at the time of the same surveys, and based upon the conditions of the beach and wave climate shown at Pescadero, the photo is most likely taken in the fall, in september or October, of either 1928 or 1929. The most probable date is the former year.

Draft Page 16

\

Management goals could be defined with the advice of state Parks anG

Recreation, State Fish and Game, sequoia Audubon, Peninsula Open Space Trust,

and local farmers. The implementation of such a management plan for the Pes­

cadero Marsh should:

(l) Insure the persistence of the marsh as a valuable natural resource by:

-controlling and protecting the marsh from erosion and sedimentation

problems within the watershed that are affecting the wetland area.

a. control amount of sediment entering marsh

b. preclude the concentrated deposition of sediment in critical areas

c. enhance sediment transport through the marsh

-controlling and protecting the marsh from pollution and contamination

problems within the watershed that are affecting the wetland area.

-excluding and/or controlling land-uses within the Preserve which are

incompatible with this goal.

-protecting the marsh from incompatible land-uses within the watershed.

-monitoring sensitive indicator species and habitats.

(2) seek the most natural and productive conditions as possible in the

preservation of the Marsh's unique ecological character by:

-improving water flushing and circulation and enhancing water quality.

-providing a diversity of habitats:

a. manage water flux and tidal influx to restore salt, brackish, and

freshwater marshes, lagoons, and upland areas.

b. maintain elevation gradients to provide a range of moisture and

salinity environments

-managing habitats to favor a diversity of indigenous species:

a. give special attention to rare or endangered species including the

Draft Page 17

san Francisco garter snake, brackish water snail, and black and

clapper rails, etc., and their habitats,

b. maintain conditions necessary for anadromous fishery,

c. control aggressive exotic plant species,

d. prevent flooding after nesting season starts to improve nesting

and reproductive success of breeding species, or provide flood-proof

nesting habitat,

-actively restoring only unstable, rapidly degrading, or important sites.

(3) Provide for local interests and surrounding land uses while pursuing

state and regional goals by:

-protecting adjacent farmlands from conditions (i.e. flooding and salt­

water intrusion) detrimental to farming operations resulting from marsh

management.

-operate the marsh in a manner consistent with the flood protection of

the town of Pescadero

-compensate for the loss of former marsh habitat in the area, by consid­

ering purchase of riparian habitat adjacent to the present Reserve boun­

daries;

(4) Be economical;

(5) Approach the goal of a self-sustaining system requiring minimal human

inputs in terms of operation and maintenance costs;

(6) Provide areas of the marsh for educational, interpretive and general

viewing purposes, while minimizing impact upon marsh ecosystem;

preserve natural visual aesthetics of area.

Draft Page 18

~· Factors Affecting ~ Resourc&

~·1· Structural Geology

The San Andreas Fault bisects the San Francisco Peninsula from northwest

to southeast and separates two major crustal blocks consisting of contrasting

rock types. The Santa Cruz Mountains are part of the structural block on the

west side of the fault which is composed of a thick sequence of cretaceous and

Tertiary sedimentary and Tertiary volcanic rocks resting on a granitic base-

ment complex. All of these rocks terminate abruptly against the san Andreas

Fault. Tertiary rocks occupy the remainder of the region, except for a wedge

of Cretaceous rocks exposed just south of the Pescadero basin on the west side

of the San Gregorio Fault. This fault is subparallel with the san Andreas and

cuts across the bas~n two to three miles inland from the coast. The Tertiary

rocks have a composite thickness in excess of 10,000 feet and consist chiefly

of sandstones, siltstones, mudstones, and shales of marine origin. The region

is very active tectonically, right-lateral strike-slip faulting moving the

western block upon which the watershed lies, approximately 5 meters /100 years

in a northward direction relative to the area east of the watershed.

Two major fault zones exist within the watershed. Their status greatly

influences the conditions in the watershed, and directly determines management

options. The Butano Fault, trending approximately along Pescadero creek,

extends from the san Andreas fault on the east to the san Gregorio-Hosgri sys-

tern on the west. This fault geometrically accommodates differential shear

between the two major plate-boundary faults: the san Andreas and the san

Gregorio-Hosgri. This latter fault system manifests a geomorphic expression

within the watershed that is every bit as recent and active as the san

Draft Page 19

s c

Andreas.

Locally, th~s san Gregorio-Hosgri fault system comes ashore near Ano

Nuevo. Gazos, Little Butano, Butano, and Pescadero creeks are all impacted by

movement of the fault. Pescadero Marsh has begun to accelerate its rate of

infilling by sediment, borne primarily by Butano creek. This acceleration 1~n'."(of.r b~ins primarily in late historic times with a rate of sediment transport

increasing for each subsequent storm flow through 1983. This is nicely docu-

mented by analysis of sequential maps and aerial photos of the marsh area

showing prograding infilling sand deltas. In a search for the source of the

sediment and the causes of its increased rates of transport or decrease in

rate of flushing through the lagoon, we began to work on the anomalous course

of Butano creek.

Many plausible reconstructions are possible, but all demand right-lateral

offset of on the order of 6 km minimum in the last 100,000 to 300,000 years.

This is the same order of offset as postulated for this fault in the Big Sur

area. Others working here have made observations of right-lateral fault

offset and come to similar conclusions using different lines of evidence

(Clark and Brabb, 1978; Weber and LaJoie, 1977; LaJoie et al., 1979).

The course of the present Butano creek northwestward along the fault zone

to its present junction with Pescadero Creek in the lagoon is quite anomalous.

Large water-gaps exist in the fault scarp-bounded upland west of the fault

line. The most prominent of these is Arroyo Frijoles. This appears to be the

westward offset extension of either Little Butane or, more probably, Gazos

Creek. Where they meet the fault, all the watercourses south of Pescadero

Creek are severely disrupted with local impounded alluvial fill sequences that

are now being incised to release sediment to the lagoon. Even the most minor

Draft Page 20

gullies are offset, consistent with recent fault motion. The course of Littl&

autano is remarkable in that it has incised several meters into its fault-line

alluvial fill along the extreme western edge of the fault zone valley.

Apparently, this location was at one time the lowest point in the cross­

section of that valley, but today that lowest point is shifting eastward to

the east side of the north-south-trending valley, leaving the Little autano

stream course "hung" like an irrigation ditch along the edge of the valley.

This is probably the result of a compressional thrust-fault component of

motion on the san Gregorio-Hosgri system with both right lateral and west-side

upward motion. such a high-angle reverse component would help to explain the

water gaps and stream capture along the fault line. Continued slow deflection

with a west-side upward component could be tilting the autano valley eastward.

Thrust components of this primarily right-lateral fault have been proposed for

the sur Thrust and Sur Hill Thrust in the Little Sur river area and in the

Hosgri offshore area. Similar observations of uplift and tilting of the

western (Pigeon Point) Block locally have been made by LaJoie, et al (op cit,

1979, p. 69) and weber has identified a thrust component in the general

ri•Jht-lateral motion of this fault zone.

Right-lateral offset rate is estimated to be 6 km in the last few hundred

thousand years based upon assumed matching of Arroyo Frijoles with the Gazes

Creek watershed, and Little autano watershed with the present course of autano

creek west of the fault zone (see Plate 3). Dating of that offset is based

upon marine terrace incision and upon interpretation of the alluvial fill

sequences in the fault valley as of late-glacial to post-glacial age. These

sequences are well exposed by redissection under present high-sea-level condi-

tions. The redissection is very recent, based upon steep channel walls in

Draft Page 21

unconsolidated alluvium, high historic sediment input to the lagoon from th~s

source, and complete absence of terrace or cut and fill evidences except those

associated with historic disturbances in the watershed within the last 100

years. The youthful character of the fill itself is demonstrated by the facts

that the fault valley itself is cut into a younger marine terrace of at max-

imum 200-300,000 years age, that the fill sequence is straightforward and sim-

ple without evidences of still-stands or soil formation in this area of very

rapid soil formation, and by observation that there are no apparent river ter-

race remnants along the walls of fault valley. we interpret this to mean that

deflection of the Butane Creek valley most likely occurred at a time or times

of lower sea levels when headward cutting along the weak fault zone was

enhanced and any earlier fill could be removed by erosion. The present fill

must postdate the last rapid rise in sea level of 18,000 to 8,000 years ago 'I i';_' )/(; 1/v.><-... '......_.,

when mature upright alders and other riparian vegetation ~as rapidly buried in ' ' \__j

this wood-rich fill sequence.

If Little Butane is assumed to have originally cut the course of the

lowermost Butane valley, and Gazos creek cut Arroyo Frijoles, then we must

propose a rate of fault motion on the san Gregorio-Hosgri fault of 2 m per

century. LaJoie, Weber, and others (op cit, 1979) estimate 1.6 m per century

of cumulative offset on this fault zone at Ano Nuevo using offset of terrace

shoreline angles.

Whatever the interpretation, many questions are raised by the relation-

ships in this Pescadero area. The timing of the capture of the headwaters of

the san Lorenzo watershed by Pescadero Creek to nearly double its watershed

area is unknown, as is the role of the Butane fault and the San Gregorio in

promoting the headward cutting of Pescadero creek to behead the san Lorenzo.

Draft Page 22

The apparent underfitness of the present mouth of Pescadero and Butano Creeks,

which exit to the sea in a single channel on bedrock at sea level in the surf

zone is very enigmatic. The buried low-sea level channel north of the present

outlet seems as misfit as the mouth of the carmel River to handle the

discharge of the present watershed areas of Butano and Pescadero Creeks. In

the case of the carmel, active post-glacial offset on the cypress Point-san

Francisquito fault has pinched off the 18,000 year-old low-sea-level channel.

Local faulting on the san Gregorio-Hosgri system could be doing the same thing

at Pescadero.

Comprehensive geologic mapping in the Pescadero Creek basin area has been (rz{ /? )

compiled by Brabb and others/\ However, the role of the San Gregorio-Hosgri

fault system which separates the Butane block from the Pigeon Point block is

not well understood. In our opinion, the recent active nature of this fault-

ing in the watershed is probably the primary cause of the potential for great

differential sediment discharge between Pescadero and Butane creeks above the

Marsh. Butane Creek, with about one fifth the area and one fifth the water

discharge, supplies five to six times or more sediment per unit source area to

the Marsh/Lagoon system. This will be explained further in the following two

sections, 5.2 and 5.3.

~·~· Geomorphology

The topography of the 81.3 square mile watershed of Pescadero creek is

dominated by regional geologic factors. Similar to the other coastal mountain

terrain stretching between the San Francisco and Monterey Bays, this watershed

displays recent uplift. Evidence of uplift on a regional scale during recent

geologic time is marked by a set of well-developed, abruptly faced marine ter-

Draft Page 23

races skirting the coastline; rejuvenated creek channels actively downcutting

into deeply entrenched v-shaped canyons; and steep slopes and generally rugged

topography in the upper reaches of the watershed. The drainage pattern of the

Pescadero Creek basin reflects equally strong regional geologic control, by

the faulted geologic structure in the underlying rocks and the northwest-

southeast orientation of the major ridges. The upper reaches of Pescadero

Creek and particularly its lesser tributaries have developed a pronounced den-

dritic drainage pattern, in contrast to its most significant tributary, Butane

creek's more parallel form along the san Gregorio-Hosgri fault. The upper

third of Pescadero Creek was apparently "beheaded" by the san Lorenzo River

watershed system in the not too distant geologic past. The headwater tribu-

taries to Pescadero creek almost all flow toward the san

Waterman's Gap, and then abruptly reverse direction when

Lorenzo valley at '0 '

th~reach Pescadero "

Creek. Thus, the upper Pescadero watershed is a new addition to the

Marsh/Lagoon system and today•s discharge may be significantly higher than

that which was responsible for cutting the main Pescadero creek canyon along

the Butane Fault.

Both Butane and Pescadero creeks exhibit a structurally-controlled rec-

tangular trellis-like drainage pattern in their headward reaches. These two

streams have gradients ranging from 15 feet per mile in the lower portions of

the basin to 1000 feet per mile in the upper portions. The only flat lands in

the Pescadero basin are the wetlands near the mouth and fluvial terraces in

the reach above Lorna Mar. Upper elevations reach 2200 to 2500 feet along the

santa cruz Mountain divide with lesser elevations along the divides of neigh-

boring coastal basins, falling to about 200 feet elevation at the marine ter-

race. Butane creek, in contrast, flows from similar higher elevations until

Draft Page 24

it is abruptly offset against the san Gregorio-Hosgri fault system. From

there to its junction with Pescadero Creek, its gradients are very low, with

gradients of 15-feet per mile or less. In the lower course of Butano, partic­

ularly where it crosses westward across the uplifting Pigeon-Point block just

before meeting the Marsh area, the stream does not even flow in a defined

channel. This aggrading reach of approximately 1 mile length comprises a sig­

nificant element of the sediment budget and wildlife habitat, thus imposing

itself into any management plan from beyond the Department of Parks and

Recreation's land boundaries.

Pescadero Creek flows in a sharply meandering channel throughout much of

its twenty-six mile length. Due to this meandering nature in deeply

entrenched channels, and due to the active uplift in the region, the stream

has historically undercut its siltstone banks eventually causing mass failure.

Debris from these slope and streambank failures diverts the force of the

streamflow to the opposite side of the channel where the process is repeated.

From about three miles above its mouth to the sea, Pescadero creek

meanders through its historical flood plain. Discontinuous erosional and

depositional terraces flank both sides of the creek in this reach providing

productive agricultural lands. Butane Creek is the most significant tributary

to Pescadero Creek, draining 21.3 square miles into Pescadero creek several

~hundreds yards above the mouth. At and about this confluence is a low-lying

flatland historically under tidal influence referred to as the Pescadero

Marsh.

Draft Page 25

~·£·~· ~ Beach/Lagoon System

An understanding of the dynamics of the marsh/estuary system requires a

very clear understanding of the beach/lagoon subsystem. The lagoon area is an

open-water system that is sometimes, but not always, connected to the open

ocean. It receives its ~ater from 4 primary sources. streamflow and tidal

exchange waters affect all parts of the lagoon subsystem, which also receives

water from direct precipitation and from influent groundwaters and minor irri­

gation return flows. That portion of the lagoon that exchanges water with the

ocean under the influence of oceanic tides is termed a "tidal estuary." At

Pescadero lagoon, the tidal estuary is today a small ephemeral area of about

15 acres maximum size that exists seasonally only when the mouth of the estu­

ary is open to the ocean and when tidal range exceeds a critical threshold

value which is itself variable as a function of beach conditions. The beach

area comprises a bay-mouth beachjbar system of semi-permanent dunes, back­

beach overwash channels, and a dynamically changing forebeach area where sand

volumes change dramatically over periods of several decades.

Every beach;lagoon system is different. Pescadero's unique management

problems derive in large measure from the unique dynamic interactions between

its beach and lagoon. Human attempts to modify this system, together with

hydrologic and geologic conditions, have created a very complex system. It is

this system, as it exists today, which has been the focus of considerable

investigation and analysis for this report. Historic analysis of maps, aerial

photographs, and ground photos has provided insight into long-term changes in

the system. Interviews and accounts of careful observations made by others

from about 1937 to the present have helped to provide intermediate-term

details. As part of the development of this management plan itself, two years

Draft Page 26

of close observation of lagoon water levels, beach conditions, tidal condi­

tions, streamflow, and beach profile surveys were conducted. Although record­

ing instruments were not available, site visits on 47 selected specific dates

between 29 June, 1983 and 1st December, 1984, when time-specific beach and

lagoon conditions were surveyed and noted, provide a detailed near-term inves­

tigative time spectrum.

The basic beach/lagoon dynamic at Pescadero follows that of other west­

coast Mediterranean-climate North American sites. In winter, with high pre­

cipitation and runoff, the lagoons are open to the sea and net transport of

sand and water is from land to offshore. Beach profiles, and corresponding

areas of tidal influence, are closely related to wave steepness, which is the

ratio of wave height to wave length. During winter, with storms moving

onshore, wave periods are short, and steepness is high. This leads to condi­

tions of net transport of sand from beaches to offshore areas. Thus beaches

become less steep and smaller during stormy winter conditions (Johnson, 1971).

In summer, wave steepness diminishes because waves are attenuated by long­

distance travel to reach the west cost. Long travel distances also tend to

insure that only longer period waves will reach this coast, because only those

can travel the great distances from southern latitudes where storms are then

extant. Thus, summer beaches are sites of net onshore transport of volumes of

sand that were temporarily stored below wave-base offshore in the previous

winter. Beaches in summer thus have low wide berms with steep beach-face pro­

files.

sand budgets for the Pescadero beach site are not complicated in theory.

Beach sands are derived primarily from onshore streams through watershed ero­

sion. Additional sources include wave erosion of sea cliffs, older beach and

Draft Page 27

dune areas. on the west side of the San Francisco Peninsula, additional sands

can be supplied by long-shore "drift" or transport from more northerly

beaches. At Pescadero, there is little doubt that the single primary source

of beach sands is the Pescadero watershed itself. As studied by Gerald Weber

(personal communication, 1984) as background to his doctoral research at the

University of California santa cruz on the origin and dynamics of beach sand

movements at Ano Nuevo, the "beach cell" of sand source, storage reservoir,

and offshore sink, is believed to be unusually simple. Rocky headlands both

north and south of Pescadero beach prevent any significant longshore migration

of sands to this site from other primary sources, such as Tunitas or San Gre-

gorio watershed to the north. A single exception may be that some of the sand

from the very small (7 square-mile) Pomponio creek watershed immediately north

appears to be able to join the Pescadero cell at rare historic times when a

near continuous beach exists between the two sites along approximately 1.5

miles of rocky coastal headlands separating their beaches.

Further, according to Weber (op cit.), the silty nature of the bedrock

units, ranging from deeply weathered volcanic rocks to partly decomposed silt-

stones and fine sand-stones comprising the sea cliffs preclude cliff erosion

as a significant source of beach sands, which are medium to coarse sand sizes /OV·.

at Pescadero. south of Pescadero, and generally the direct of net "down­/\

drift" of beach sediment transport, the rocky sand-free headlands immediately

adjacent to Pescadero Beach attest to the fact that its sands cannot/ be (now /\

being transported to other beach cells in that direction. The dramat,ically ;.; ,,. ~~~~-

different beach sediment conditions ~ Pescadero beach :tn-eompa5~tQ,

beaches immediately south demonstrates that sand that is lost offshore from

the Pescadero cell is carried far offshore at the headland at the south end of

Draft Page 28

Pescadero beach, and cannot be recovered by subsequent, long-period non-storm

waves. Thus, we see that the Pescadero sand transport system is simple with a

single source in its watershed, a single beach and dune storage area, and

probably a single offshore depositional sink. This understanding is a very

important element for subsequent hypotheses on causes in variations of Pes­

cadero beach volume.

At Pescadero, as has been long observed, the lagoon remains open to the

sea only when runoff is sufficient to overcome the natural tendency of

longshore sand drift to close the mouth of the lagoon with a beach spit. This

naturally occurs in winter "WWn!n' when the combination of high runoff and

short-period storm waves create both a lower beach berm and a higher lagoon

water level. Throughout the california coast, the popular perception of

residents is that the runoff "overtops" the beach-bar, and the lagoon opens.

rn fact, this is only the case during major runoff events. More commonly, the

first winter storms produce progressively greater runoff and lagoon water lev­

els rise, usually because they are gaining water from both runoff and from

high-tide wave overtopping. So long as the water entering the lagoon does so

at a rate less than that equal to its combined evaporation from the lagoon

surface plus its natural rate of leakage through the highly porous blocking

beach berm, the water surface elevation will not rise by a net amount. But in

late autumn, when evaporation decreases, rainfall and runoff begin, and high

tidal ranges associated with cyclonic storm fronts occur, water levels may

rise in the lagoons to such an extent that the gradient on the water surface

of the percolating groundwater.s seeping out of the lagoon through the beach is

steep enough to erode the forebeach. At these times, the beach becomes very

vulnerable to wave erosion and breaching often occurs. This may occur when

Draft Page 29

the lagoon water surface level is still lower than the height of its impound­

ing beach berm.

Although theory can be used to explain most of the observations of the

casual observer, real beach/lagoon dynamics are most often much more complex.

At Pescadero, the combinations of modifications associated with highway and

bridge construction along the beach berm itself, coupled with both the tem­

porary and permanent measures taken by local residents to reduce the seasonal

rise of water levels in the lagoon, have created conditions where general

theory alone cannot entirely explain the present and past lagoon and beach

dynamics.

The Pescadero beach/lagoon system has historically comprised a single

beach unit, approximately 3,700 feet long (Pescadero state Beach), backed by a

back-beach dune field (the present location of State Highway one), and enclos­

ing a back-beach lagoon and seasonal tidal estuary system (North Pond, the

pond at the west margin of North Marsh, and the delta lagoon/estuary itself).

This is the beach-lagoon system, although of course it interacts with and

comingles with the marsh-river system formed east of it. In the first accu­

rate topographic map of 1854, we can see rather clearly how this system func­

tions. The small bedrock headland jutting onto the beach where the state

Parks parking area northwest of North Pond is situated today, was the north­

ernmost limit of the backbeach dune field. That dune field is depicted on the

1854 map as reaching elevations of at lest 20, and possibly 40 feet above sea

level (the highest dunes today are similarly about 40-feet above mean-sea­

level). The dunes are shown as having been actively modified by northwesterly

winds (while they are today stabilized by introduced vegetation and the high-

way). In 1854, the dune field and its fronting beach is shown as wrapping

Draft Page 30

eastward at its southern end, into the estuary. This is precisely what we

would expect today if the dunes were not stabilized by vegetation and highway

surfacing, and if the tidal volume moving into the lagoon were sufficiently

large to transport sand there by longshore drift.

Most significantly, the 1854 map reveals the topographic low spot at the

extreme north end of the dune field where seasonal overwashing charged the

back-beach lagoon system behind the dunes. The "full" character of North Pond

and its overflow extensions to the south, and the depiction of marsh open-

water vegetation (quite probably cat-tails) north and south of North Pond, but

nowhere else in the entire area of Pescadero marsh, most certainly indicate,

in 1854 at least, the area immediately east of the dune field was a periodi-

cally replenished salt-water lagoon. The 1928 aerial photo also shows clear

evidence of overwash into North Pond in the not too distant past, but that

photo also suggests that some activity in the recent past may have graded a

possible road alignment along the crest of the dunes, at the location of the

present state highway. This may represent preliminary grading for the pro-/fil ,1 '

posed Ocean Shore railroad. Photographic interpretations of this grading ·'::';;(""''

ambiguous, but high quality ground photos taken by the state Highway Depart-

ment in 1937 and 1938 along their proposed right-of-way, also show what

appears to have been evidence of some previous grading. It thus may be that

the North Pond salt-water overflow was cut off as early as 1927 or 1928, and

certainly by the time of state highway construction in 1939. Local residents

over 60 years of

into North Pond.

age report recollection of direct exchange through the beach

.,.!\ Wave swash associated with a storm tide reached a' estimated

6.9 feet above mean sea level in November, 1983, and would have overwashed

into North Pond had it not been for a berm of logs and rocks south of the

Draft Page 31

state Parks parking kiosk and the state highway berm.

Geologic evidence lends further insight into the beach/lagoon dynamic.

Old stabilized fossil dune sands exist north of the present limit of dunes,

around the state Parks parking area. Other dune sands mantle the hillside <',::1•

south and '"·eaeh-·of North Pond. Under today's environmental conditions, these

deposits could not form. The beach northwest of the parking area is propably CoY', { ,:-)_ j "J,

too small to provide a source for the older dunes there, and the ~~ of

the North Pond lagoon system precludes transport ~ of sand from the beach

source to the hills across the lagoon. Thus, in the geologic past, there must

have existed times when the beaches were wider and lagoons did not exist in

their present localities. This past condition and subsequent change is '=""'""'"""'

throughout central california's coast.

Within historic times, the North Pond has been farmed (see Fig. 6 indi-

eating farming between 1941 and 1956 as shown on photos of the latter date)

and today it is isolated by road fill on the west, and by a partly-plugged

valved pipe beneath an artificial dike or barrier to the south. Apparently,

d this system ha~been manipulated ~s to allow the pond to drain

or be pumped dry at times of low g~t:i~ri11:1,, lagoon levels. An artificial

drainage channel around North Marsh probably aided in this activity. Today,

North Pond shows evidence of rather rapid filling from the east by fluvial

transport from a deeply-incised gully system. Swanson (1982) has studied the

history of development of these gullies. Biological oxygen demand (BOD) rises

to levels sufficient to suffocate most larger aquatic animals by late summer,

since regular recharge for North Pond today is primarily restricted to surface

runoff and direct precipitation sources in wintertime only. At times of high

Draft Page 32

water levels in the lagoon (6 feet msl or greater), positive flow to North

Pond is possible and is seen to occur, very slowly, through the single

drainage pipe of unknown effective diameter at its south end.

History of~ change has been studied using aerial photos and maps.

Table 1 summarizes these data:

Draft Page 33

CHANNEL DISTANCE PT. DISTANCE DATE CONDITIONS TO SHORE* SHORE TO RD**

1854 very wide 450" indeterminant

1928 very narrow 8' (even) ±500'

4-11-41 fully open 370' 260'

10-11-43 closed 170' 370'

4-24-48 narrowly open ( 38. ) 170' 388'

5-27-56 narrowly open 170' 375'

5-30-57 narrowly open ( 30. ) 120' 440'

l0-13-63 narrow ( 20-40 • ) indeterminant 450+'

2-3-67 fully open 230' 450'

5-15-68 very narrow 160' 500'

5-4-77 closed by 100'-wide 0' (even) 500' sand-bar

5-15-88 narrowly open 280' 433.

6-23-88 tunnel outlet only 280' 430'

1-7-82 fully open 300' 390'

* Distance between MH8W float line and survey point AR144 (39.54') in a due­east-west line. This point is the rocky point directly above the tunnel.

** Distance between west edge of state highway pavement and MHHW line of drift on beach due west. survey transect point is approximately 1000' north of north Hwy one bridge abutment.

All data derived from aerial photos except 1854 map (Fig. 1).

Table 1. Historical beach widths, Pescadero Beach

As can be seen from the available data, Pescadero beach does not simply change

with the seasons. The beach was very narrow at the time of the 1854 topo-

Draft Page 34

graphic surveys, and in spring of 1941, and in early 1982. An invaluable com­

pilation entitled "Storm History of Monterey Bay and the central California

coast" (Garry B. Griggs, personal communication, unpublished) from 1918

through 1980 shows that the April, 1941, photo-data represented conditions

immediately following two successive winters of highly erosive winter wave

conditions. Three destructive storms of 1939-40, with deep-water waves of

20-25 feet were followed by 4 very destructive southwesterly storms in the

1940-41 winter which closed Hwy one, eroded large areas of beaches and other

coastline, and flooded homes in Half Moon Bay one foot above their bases. The

last storm of 26-28 February, 1941, smashed the steps of the santa Cruz

casino. Other heavy beach erosion periods were reported in 1926-27, and again

in 1931. The latest major erosive storm ended just three days before the

January, 1982, photos were taken.

The beach was very wide in 1928. After its erosion in 1939-41, it

apparently became progressively wider through the SO's, 60's and 1970's.

Storms in 1978 and 1980 diminished the beach volume somewhat, and that of

January, 1982, significantly reduced its overall width. One must be careful

interpreting incomplete data sets, such as aerial photos. Doubtless, one

gains an oversimplified impression of beach dynamics. However, the available

data, coupled with other newspaper and eyewitness observations, support the

following hypothesis of beach dynamics at Pescadero.

Beach sand volumes are controlled by sediment load of Pescadero and

Butano creeks, and by wave climate at the beach. When sediment discharge is

high, relative to the ability of waves to carry that sediment beyond the depth

of wave-base, then beaches prograde and increase in volume. When local winter

storm conditions are less severe than normal, while distant Southern Hemi-

Draft Page 35

sphere storms generating long-period waves are normal, all sands in offshor&

storage above the level of deepest wave base can be moved onshore. such con-

ditions occurred in 1977, at the end of the longest historic period of winter-

time high pressure blocking ever recorded. Beach widths and heights are maxi-

mal at such times of sequential years of absence of normal winter storm pat-

terns at the latitude of Pescadero. The mid- to late-1920's were apparently

another such period, as possibly was the period from 1935 through 1937, based

upon climatic and runoff records.

When beach height and width is greater without high runoff, the lagoon

levels reach their highest historic maxima. The year 1977 was one when this

effect was clearly demonstrated and well documented. 2 In the 1977 instance,

repeated attempts to open the lagoon to the sea by cutting channels through

the beach in December, 1977, failed to stop the rising levels of saline water

in the lagoon system, which was closed to the sea but receiving overwash from

the first post-drought storm waves at times of maximum annual high tides.

Water levels reached at least 9 feet above mean sea level, with a closed

lagoon and no evident runoff increase above base flow for Pescadero creek.

Only repeated uses of heavy earth-moving equipment could combat the natural

tendency of longshore sand drift plus channel-side collapse that would close

off channels dug through the beach to drain the lagoon.

The report by the state of california Highway Dept. of July 1939, for the

proposed Pescadero Highway 1 bridge (Brumunel, 1939) reports that "probably in

2This record is best reviewed in the court records of the san Mateo co. Su­perior Court case No. 222928, Tommy Phipps et al. vs. state of California, of 1984. This case reviewed the claim by Phipps that high water flooding during california's 100-year record drought was exacerbated by conditions at the mouth of Pescadero Creek that were purported to be under the control of the state of california.

Draft Page 36

1937" high water in the lagoon reached an approximate elevation of 18 feet

above msl, flooding the approaches to the old Pescadero Road bridge over

Butano Creek. Their investigators found some "questionable drift" evidence of

earlier water levels to 11 feet. In our analyses, we readily found drifted

logs of some antiquity judged by their partly rotted character, surrounding

the marsh/lagoon system to elevations of 11 feet. These maximum drift lines

were noted to be horizontal, not inclined seaward as would be expected if the

lagoon mouth were open. It is thus reasonable to postulate that conditions

like those of 1977 typify some times of highest lagoon flooding, and that

major flood heights are not always associated with peak runoff. As will be

shown in Section 5.3 on hydrology, the maximum flood of record in 1955 pro­

duced flood elevations very close to those apparently controlled by maximum

beach heights. The December 23, 1955 runoff flood produced water levels that

varied between 9.4 feet at the mouth to 11 feet at the upstream limits of

state Parks property.

In summary, beach volumes and height vary as a function of both watershed

and external factors. When high runoff volumes do not occur until November,

December, or later, conditions are set up for maximum lagoon flooding by salt

water. This occurs when the extreme high tides of early winter (tides of +4-5

ft msl, or +6-7' MHHW as reported in the tide tables) coincide with approach­

ing steep water storm waves that can swash over the blocking bay-mouth bar,

filling the lagoon at high tides, but not letting it drain at the lower tide

times.

Humans have influenced or attempted to influence the beach, and hence the

lagoon, for as long as the area has been used agriculturally (the 1850's

according to the San Mateo County Historical Society, personal communication,

Draft Page 37

1982). At some time prior to, or near the end of the last century, based upon

historic photographs and the memories of the oldest local lifelong residents,

a tunnel was constructed that penetrates the rocky point on the left bank of

the outlet portion of Pescadero Creek. We can now only speculate why the tur1-

nel was constructed through solid rock in the tidal zone. The tunnel effec­

tively prevents the lagoon level from reaching elevations above two or three

feet above sea level when the beach is wide enough to terminate and block the

river mouth against the rocky point. These conditions did not exist in 1854,

did in 1928, but did not at the times of observations in the 40's, SO's, 60's

and early 70's. Then, in the late 70's and early 1980's, the tunnel again

functioned to restrict lagoon elevations during many years. The tunnel works

like a one-way filter or rectifier. It permits the passage of sediment (and

water) into a different beach sediment cell from that of Pescadero Beach.

Although the bedrock bed of the tunnel is insufficiently deep to accomplish

much sediment transport (its bed is -0.31 ft ms1), sand that does go through

it is either stored temporarily on the small pocket beach just south of the

tunnel mouth, or is most often carried offshore through the rocks and dropped

below wave base. When the beach is narrower than about 400 feet width, the

baymouth bar closure takes place upstream of the tunnel opening and it can

have little effect on ultimate lagoon heights. Thus, for example in the

1950's, most of the 60's, and the 1970's, standard practice among those farm­

ing the agricultural lowlands in the marsh was to dig or bulldoze an artifi­

cial channel through the beach at its narrowest point, usually near the rocky

point adjacent to the tunnel site. This was done, generally, when water lev­

els reached about 6 feet above sea level (Phipps, personal communication,

1983). At this point there would still be about 1-2 feet of freeboard on mosL

of the dikes protecting farm-lands.

Draft Page 38

It is tempting to speculate that the tunnel was constructed during th~

times of maximum sediment discharge that would have been associated with the

period of initial intense logging activity in the Pescadero creek watershed

proper, in the 1880's and 1890's. This would have been a time when, under

lagoon diking then in effect and flood runoff from the major storms of 1878,

1879, 1881, 1889-90, 1894 and 1895, maximum sediment transport down the river

and through the lagoon to the beach would have occurred. Although wave condi­

tions are not known for that time, high sediment flux alone could have sup­

ported a wide beach with opportunity for relief of lagoon elevation with the

"permanent" bedrock tunnel.

The damming of the entry to the North ~ Lagoon by road construction

has had a major influence on the system. Obviously, the lagoon system can no

longer be flushed with salt water on a periodic basis, and under no cir­

cumstances can the lagoon be drained dry as may be the case rarely when large

storms and floods removed a major portion of the back-beach dune field and the

lagoons are exposed directly to tidal action and wave attack. With a mean

surveyed elevation of the North Pond surface of about 5.0 feet today, very

little exchange of any sort can take place in North Pond. Sediment thaL

enters the pond through hillside erosion will ultimately fill it since the

highway location and rip-rap protection, masked by dune sands, fully precludes

wave attack and erosional removal.

Another more remarkable and rather obscure effect of the location of the

Highway ~berm was not realized until the November 5, 1983, beach surge over­

topping event. At that time, storm tides of +5 to +7 feet msl allowed waves

to surge over the forebeach and pool against the dune field in a lower back-

beach area. The lagoon mouth was closed by a bar. The ponded backbeach

Draft Page 39

waters could not enter North Pond because of a stone and log protective work

across its natural entrance, and because of the highway berm beyond that bar-

rier. These waters thus ponded and flowed both north and south from the

center of the beach where wave run-up was greatest. The north-flowing portion

of the circulation cell reentered the sea through a low spot in the forebeach

at the north rocky headland. The south-flowing portion entered the lagoon

(Plate 2). During the course of the period of highest tide, sufficient water

entered the lagoon to raise its level 0.2 foot in one-half hour. The water

flowing along the back-beach formed an erosional channel in which it flowed in

upper-regime (super-critical) flow at high velocities (Plate 3), The flow

entrained and transported clasts to 20 em median diameter across the delta

that was then rapidly forming in the lagoon, and deposited them in the area of

the normal thalweg of the usual outlet channel. Although some of the clasts

were rounded and bored by marine organisms, and thus probably derived from the

beach itself, others were subangular sandstones of the type found within the

dune field as the foundation for Highway one. / -·"----.. ,_ '

These clastp; matched ,lithologi-_, \ "---·~---

cally others removed from the site of their observed November 5 deposition

when CalTrans, the state highway agency, excavated there on two occasions

prior to July, 1983, to attempt to effect a less obstructed course of outflow

for Pescadero creek (see before-mentioned court records), we thus see that

the blockage of the normal North Pond lagoon circulation pattern forces the

development of an overwash circulation pattern that carries sediment directly

into the area where lagoon breakout must ultimately occur. Through aerial

photo analysis we see that this washover delta is frequently observed in the

area of the Highway One bridge. It will be shown in Section 5.3 to be a sig-

nificant element in the reduction of tidal flushing of the lagoon. The normal

development of washover deposits would not be expected to impede beach

Draft Page 40

breakout (Pierce, 1970).

The Highway ~ Bridge design and location is then a final element in the

human influences upon the beach/lagoon system. Long a point of contention by

local residents, highway bridge design has been seen as a primary cause of

impeded drainage of the lagoon and subsequent flooding of marsh lands put to

temporary agricultural uses. There is no question that the location chosen

for the bridge span restricts the location of any potential Pescadero estuary

outlet to a position hard against the south end of its beach-bar. From a

marsh-management viewpoint, the primary questions to be asked center around

the magnitude and character of effects that the bridge may impose upon the

lagoon-marsh area in comparison to those to be expected under pre-bridge con-

ditions when the system was self-maintaining. Looking at the 1854 map (Figure

1), and the numerous pre-bridge photos taken by the state highway engineers

(CalTrans, san Francisco Offices, personal communication and file review,

1983), as well as the research done by Violis (1979) and the 1928 aerial

photo, we can see that at all historic times for which documentation is avail-

able, the outlet was in the position we see it today. In 1854 the entire

beach/dune ridge is farther east than it is allowed to exist today, owing to

the position of the rip-rap-protected north bridge abutment and highway berm

(Plate 4). In their proposed bridge design report of 1939, the state highway

department (Brumunel, 1939, p 13) cites eyewitness accounts of historic pre-

bridge flow" ... to a width extending to the north sand dunes, of approxi-

mately 280 feet wide." The 1928 pre-bridge photo shows the beach prograded

westward to and beyond the rocky headland, with longshore sand transport

' down-coast south of the creek outlet. However, it d-.a also clearly show;\· the

"hook" at the south end of Pescadero beach, extending back into the lagoon

Draft Page 41

area just as seen in the 1854 map.

From these observations, we conclude that the effect of the location and

design of the highway bridge does not affect the site of the Pescadero creek

outlet, which is controlled primarily by longshore beach drift and dominant

northwesterly winds carrying sand in the form of dunes to further restrict

flow to the south end of the beach. Effective outlet width today, 260 to 270

feet, is not significantly different from the 280 feet observed historically,

although the highway engineers may have erred in assuming that the dune loca­

tions they noted in 1937 and 1938 were the same as those cited by their

eyewitness informants as defining the natural channel width. The primary

effect of the bridge location is to limit the amount of beach erosion that can

occur by ocean waves, which in turn restricts the location of the outlet chan­

nel of Pescadero Creek at rare times of minimum beach volume. Not since the

highway berm and bridge were constructed has there been a time when the posi­

tion of the MHHW line on Pescadero Beach has been significantly affected by

these bridge highway works. If, on rare 100-year or greater interval times,

when extensive and persistent erosional storms removed both beach and dune

field, then the stream outlet will not be allowed to swing northward at the

approximate position of the north bridge abutment today--IF the highway berm

and bridge abutment survive such an erosional period.

Dunes have been stabilized to some considerable degree by both deliberate

plant introductions (such as marim grass) and by inadvertent colonization

along roadsides (Frenkel, 1970). Sequential aerial photos show the effects of

this stabilization, especially in the "hook" area where replenishment of sands

eroded by high flood flows in 1955 has not occurred. The bridge location and

berm construction may have affected this stabilization in minor ways. The

Draft Page 42

stabilized sand surfaces probably restrict storm wave erosion somewhat, thus

protecting the highway berm and bridge abutment.

~·~·~· ~ Marsh/Stream System

The functions of the salt-marsh, the freshwater marsh, and their inter­

faces to surface streams are better known than those of beaches, lagoons, and

tidal estuaries (see for example, Teal and Teal, 1969). In coastal california

the infilling of coastal marsh lands primarily by river-borne sediments has

been well studied (Atwater, Hede1, and He11ey, 1977; Nichols and Wright, 1971;

Atwater and Hedel, 1976; Bergquist, 1978; Addicott, 1952; Rowntree, 1973).

At Pescadero, the normal progressive infilling of drowned coastal valleys

by terrestrial sediments following sea-level rise has been modified primarily

by the factors of active tectonic modification of the valley topography during

infilling and by construction of dikes and levees. The former actions will be

discussed in detail in the next section (5.2.3). The effects of diking upon

natural marsh/stream system function will be discussed here.

As can be seen from the distribution of natural levees on the 1854

1:10,000 accurate topographical map, sediments entering the low-gradient coa­

stal portions of stream courses were deposited largely by overbank deposition.

The resulting natural levees and associated stream deposits comprised fine

sands and silts deposited in single depositional units with thicknesses that

varied from inches to a foot or more. In this climatic region with but a sin­

gle runoff season, winter sediment loads would be largely deposited near the

heads of the marshlands, where the stream gradients first become flat. This

is the area at Pescadero of the approximate eastern limit of State Park land.

rts position is determined primarily by tidal and beach-bar controlled

Draft Page 43

positions of zero-gradient water. At Pescadero, this transition between

stream and salt-marsh occurs between 9 feet above msl and 11 feet msl. While

it is true that saline water conditions at those elevations do not occur even

annually, that elevation is also the elevation of "backwater" flood heights

(see section 5.3) formed as floodwaters pool in the marsh/lagoon area during

high runoff events, before flowing seaward through the narrower beach opening.

Thus, the natural function of the stream(marsh interface is to be an area

of deposition for terrestrial sediments at the tidal interface. These sedi-

ments are deposited in units that are thickest immediately adjacent to the

watercourses where changes in stream velocity are greatest during times of

large magnitude floods when the marsh area is generally completely flooded.

These times coincide with periods of highest sediment transport. Only a few

percent of the annual peak floods transport 70-80 percent of the total sedi-

ment volume. Since major floods are restricted to 10- to 20-year return

periods, the "normal" appearance of the marsh depositional areas is that of a

vegetated low-gradient wetland.

Absent human intervention at Pescadero, we would still see raised broad

dike-like levees along the watercourses of Pescadero and Butano creeks where

they pass through the marsh areas, between elevations of S-6 feet msl to 9-11

feet msl or higher. This is the zone of natural deposition of sand and silt

sized terrestrial sediments. coarser cobble-sized sediments are carried by

the streams in high flood stages, but are generally deposited only within the

stream channels themselves. At times of lower tides and open lagoon condi-

tions, these channels are well defined all the way to the beach mouth, and /{ '·· ,,,.·

coarser sediments .. re carried along the entire channels. At higher tidal con­!\

ditions or times when inflowing waters are ponded by backwater, as is most

Draft Page 44

often the case in truly large floods, the areas of deposition of coarser sedl­

ments are near the eastern margins of the Preserve, and overbank deposition of

fine fractions is widespread.

once deposited in the marsh areas, the fine sand and silt-sized materials

undergo compaction, generallY becoming reduced to 60 percent or less of their

original thicknesses (Weller, 1959). At Pescadero, our soft-sediment coring

was generally not effective to depths greater than 4-5 feet. From it, we

learn that past depositional conditions throughout the marsh areas generally

are most like those in the undiked portions of Delta Marsh today. There we

find depositional units of sand and silt up to two feet thick near water­

courses, overlying layers of organic muck with leaves and twigs remaining

identifiable in an oxygen-poor environment. In channels, layers or well-

rounded stream gravels at maximum only a few inches thick, separate every

major flood deposit. These grade upward into post-flood organic muds and

peats (gytja), and are then in turn capped with another flood deposit sequence

beginning with coarse sand or gravels. The flood deposit units could be

correlated with runoff records to form the basis of an assumed, unverified,

depositional chronology going back to 1955. The flood deposits of 1955 were

generally so coarse that they could not be penetrated with our simple l-inch

diameter coring tools. If our assumed correlations with years of major depo­

sitional events is incorrect, and what we assume to be 1955 is in fact 1964,

or even 1939, the conclusions we draw are not invalidated.

We find that, at Pescadero, the primary effect of the construction of

artificial dikes has been to shift the zone of maximum deposition of sediments

away from the upper marsh and to concentrate it in the stream channels them-

selves, and in the lower marsh/lagoon area. The stream channels have

Draft Page 45

apparently had to greatly increase their gradients to carry their imposed sed-

iment loads. This has been done by progressive aggradation of the channels

between dikes. The steeper resulting gradients result in a system where

stream gradients do not change abruptly at the back edge of the marsh habitat,

and where sediment transport efficiency is increased across the marsh areas.

The narrower, steeper artificial stream channels carry sediment directly

across the marsh into the lagoon area. The channel aggradation results in

decreased channel capacity and extends well upstream from the Preserve boun­

daries. These results explain the observed changes in the marsh/lagoon sys­

tem. Violis (1979) reports a 54.1 percent reduction in the size of the tidal

delta;open water area between 1900 and 1960. our figures 4, 5, and 6, showing

the progressive encroachment of farms and dikes to the areas originally

flooded as tidal marsh, as well as the Violis data, indicate that the greatest

reduction in marsh area (29 percent) occurred between 1930 and 1960, the

period of greatest agricultural expansion and, not insignificantly, the period

of greatest reduction in major floods.

we have observed through coring, and local residents (Camponetti, per­

sonal communication; Duarte, personal communication) have corroborated through

eyewitness memory, that the upper course of Butane Creek, at least, has

aggraded 5-6 feet in the vicinity of Pescadero Road bridge at the edge of the

Preserve since approximately 1955. Even greater aggradation is suggested by

the county highway records of reconstruction of that bridge, and by the deep

large-diameter coring done at the bridge-site for that purpose (San Mateo

County Public works Dept. records) since about 1910. Comparable aggradation

of Pescadero Creek cannot be clearly demonstrated, although it may have

occurred.

Draft Page 46

Thus, we see that the natural functioning of the marsh/stream system as a

sedimentation basin has been changed somewhat by the activities of people

using the marsh areas for agriculture. Through increased transport capacity

for sediments but decreased possible depositional areas, more recent deposi-

tion has been concentrated in the channels themselves and in the lower

delta;lagoon area. This has decreased the carrying capacity of the stream

channels, and greatly decreased the lagoon area that can potentially function

Q,

as a tidal exchange are' when the system is open and functioning as an estuary.

Another functional change brought about by agriculture has been the

change in salinity gradient across the salt marsh. Although no data are

available on salinities of the marsh before intervention, the vegetation as

mapped in 1854 strongly suggests salt marsh (Shalowitz, 1964; Nichols and

Wright, 1971; Brewer, watson and Gray, 1876). Analysis of soil salinities by

local farmers and for this study shows that surface soils within the entire

area mapped as marsh in 1854 are today saline in summer, particularly if fal-

low. Local soil salinities at the upper (eastern) margin of the marsh area

were found to vary from 10-25 ppt, or up to 70 percent that of sea water.

Natural function in the undisturbed salt marsh would be to expect seasonal

brief flood mixing of saline overwash and low-water lagoonal residual waters

in late fall or early winter. This would normally be followed by rainfall

flushing of salts from surface soils, and by occasional overbank runoff floods

of fresh sediment-laden water in winter. In this fashion, soil salinities are

maintained in the maximum range of 5-10 ppm. Today•s higher salinities sug-

gest that the diking may reduce overbank flood frequencies which in turn

reduce flushing action or periodic burial. However, an alternative hypothesis

is perhaps more plausible. The agricultural clearing of salt-tolerant vegeta-

Draft Page 47

tion, and the plowing of these soils for planting to artichokes or other crops

without full cover or evaporative demand, may allow progressive increase in

salinity of surface soils through evaporative transfer upward in the soils.

When crops were being grown actively, as they are today in the Water Lane

area, high input of irrigation water serves to leach salts downward so long as

water tables remain below root zones. Under these conditions, surface soil

salinities drop to a few parts per thousand. With abandonment of crops after

state purchase of lands, salinities have been progressively rising. With a

return to flood flushing in winter, and a return to seasonal fluctuation of

groundwater table fluctuation, the original salinity conditions, whatever they

may have been, should be possible.

~·£·1· Sea Level ~ Tectonic Controls

The special conditions at Pescadero Marsh brought on by the combined

effects of rising sea level and active deformation of the earth's surface

deserve special discussion in this report. These are entirely "natural" fac­

tors affecting the marsh resource, and the problems at Pescadero are not

unique. In California, the two lagoons of the Point Reyes peninsula and the

small marsh at the mouth of the Carmel River are also strongly affected by the

same combination of sea level and tectonic controls.

All coastal estuary-marsh systems owe their existence, more or less, to

sea level change. coastal marshes are generally old valleys that have been

drowned by rising postglacial sea level. west-coast coastal marshes are gen­

erally much smaller than those on the east or Gulf coasts of North America

because the west coast is generally raising itself, thus decreasing the effec­

tiveness of rising sea level alone to flood large valley systems such as that

Draft Page 48

of the Potomac or the Delaware river valleys. Also, western us coastal marsh

areas are more often flanked with high rapidly-eroding mountains made up of

geologically young soft partly consolidated rocks that are highly faulted.

They thus tend to fill-in faster under a higher sediment flux.

sea level ~ is a universal worldwide feature affecting all coastal

areas. careful work in the san Francisco Bay area by Atwater et al. (1977)

show that for south san Francisco Bay, at the latitude of Pescadero, sea level

rose on the order of 1 m every 60 years during the period of maximum ice

melting-rate from over 10,000 years ago to about 8000 radiocarbon years before

present. Then it slowed rapidly over a 2000-year period to rise at an average

rate of l m per 600 years for the last 6000 years. These are average figures

only and do not indicate the many fluctuations that are known to have occurred

during that time interval (Scholl and Craighead, 1969; Milliman and Emery,

1968; Hicks, 1968). At Pescadero, we can see from the exposed sediments in

the walls of the lower Butano and Pescadero channels where they pass through

the upper filled valleys in the present agricultural areas, that the order­

of-magnitude change in rate of sea level rise 6-8000 years ago markedly

changed local conditions.

We reconstruct, based upon degree of preservation and sedimentary struc­

tures, that sea level rose fast enough to stay ahead of generally rising land

mass until about 7000 years ago. coastal valleys were drowned up to sites

with a present elevation of about +100 feet msl. Like other coastal Califor­

nia areas, lowland alder, willow, sycamore, and redwood were flooded out and

buried in growth position by rapidly-rising sediment levels. The sea/land

interface was at least as far inland as the present town of Pescadero and

probably farther south and east. Most of the Butano valley along the San

Draft Page 49

Gregorio-Hosgri fault trace was upland freshwater marsh, like the area along

that creek known as the "alder thicket" is today., Then, as the rate of sea

level rise decreased, valleys ceased to drown and the shore interface gradu­

ally shifted westward. Today, after 7000 years of slower sea level rise, the

land has again outpaced the sea to exhume up to 50 vertical feet of land that

was once filled and below sea level. This is the area of the southern and

eastern agricultural lands along the two creeks, where the watercourses are

today incised at least 50 feet back down to the old mid-glacial forested val­

ley bottoms. Aside from the interesting fact that this means that some

waterlogged stumps and logs now washing into the lagoon died 7000 years ago,

we can use this information to reconstruct the current rates of land movement

and thus predict the future effects upon the marsh habitat.

Assuming that sea level has been rising approximately 0.54 feet per cen­

tury (1m in 600 years) for the last 7000 years and that during that same time

interval the land has risen 50 feet or more than sea level has risen, we can

estimate a net rise of 88 feet (27m). This gives us a rate of tectonic

uplift of the land area of about 1.26 ft per century, or about 10-times the

long-term (greater than 100,000 per year) regional rate along the southern end

of the santa Cruz Mountain block at santa Cruz. such high rates of uplift are

not unusual on the west coast, and much higher rates exist at Ventura, cape

Mendocino, and southeastern Alaska. Nonetheless, it is a substantial rate and

has significant management implications.

Into the foregoing discussion we must also place the perspective of the

implications for predicted changes in rate of sea level rise. The half-foot

per century rise in sea level that we note for the last 7000 years based upon

geologic data for the San Francisco Peninsula/Bay area is also demonstrated by

Draft Page 50

current long-term tide station records (cr. Hicks (op.cit.) who found 0 ' . . " '',)

rise at San Francisco between 1907 and 1968). Prediced effects of ongoing f\_

changes in atmospheric gas content, while still debated in terms of degree of

effect, are certain to have a net effect of at least a short period of more

rapid sea level rise. Thus, the rapid net uplift of the land, which would

tend to shift the beach-boundary westward and steepen seaward sediment tran-

sport gradients, may tend to be compensated for to some unknown degree by

rapidly-rising sea level, which may prolong the life of Pescadero as a salt-

marsh and estuary.

Today•s net rise of the land at a rate greater than that for the rise in

sea level is, of course, a possible primary reason for the diminution in tidal

exchange and flushing at the Pescadero estuary. However, it cannot explain

all of the tectonically-controlled conditions. As has been mentioned before,

the San Gregorio-Hosgri fault, which offsets the Pigeon Point block progres-

sively northward relative to the headwaters of Pescadero and Butane creeks,

has been responsible for much of the anomalous topography of the lower water-

courses. The net effect of this progressive offset is to lengthen the lower

stream courses, across their already low-gradient filled valley reaches. The

course of Butane Creek is being extended on the order of 10 feet per century

(6 km/200,000 yrs), but there is some evidence that this offset does not all

occur in one fault zone. Heyes (1977, 1981) was the first the note the

anomalously shallow depths to bedrock based upon core drilling along the south

end of Pescadero Beach. No data are available in the center of the north-

south beach alignment, but it is evident from wave diffraction patterns and

low-tide visibility that bedrock exists at shallow water depths immediately

offshore barring at least the southern 1000 feet of the beach. Some offshore

Draft Page 51

nearshore rocks are seen by study of the sequence of available aerial photos

to occur throughout at least 1500 feet, or the southern half, of the beach

length. This fact, coupled with the alignment of the northern margin of the

remnant of the coastal terrace in the Pescadero Reserve boundary and it linear ?

extension into a series of dry valleys south of Pescadero Road, through the

"alder thicket" area, to join the main trace of the san Gregorio-Hosgri fault,

all strongly suggest an active trace of that fault passing along the (left mar-

gin of the marsh and lagoon area, passing under Highway one about 1000 feet

north of the bridge, and trending out to se?-in a northwesterly direction,

presumably to join an offshore trace of the san Gregorio-Hosgri system. This

fault is speculative. Its trend would parallel that of the Butano fault along

the upper watercourse of Pescadero Creek, and its structural function would

presumably be the same as that fault. It is a right-lateral shear-coupled

northwest-trending transverse strike-slip and thrust fault joining two seg-

ments of the main transcurrent plate boundary faults as they come together

offshore just north of the Golden Gate to form the northern trace of the San

Andreas fault. Its presumed presence would help to explain why, north of Pes-

cadero watershed, the "main" trace of the San Gregorio-Hosgri fault is so much

less well defined and topographically distinct in comparison to its course

along Butano Creek. It would also help to explain the remarkably different -+o

bedrock types exposed ~ very close p~ each side of the presumed

fault at opposite ends of Pescadero Beach. The volcanics to the south are

presumably older and should be much lower in the section compared to the mud-

stones cropping out at the beach parking area and to the north (J. Clark, per-

sonal communication, 1984; Glen, 1959).

Draft Page 52

Whether the fault exists or not, it appears clear that the south end of

Pescadero Beach is rising, and probably moving north, relative to the

marsh/lagoon system. This tends to raise the marsh outlet above sea-level, I k·v:;

virtually defeating tidal exchange, and further decrease$,~Seaward gradients

for the lower reaches of the sediment-laden streams. A right lateral offset

rate of 5 feet per century, or one-half that for the san Gregorio-Hosgri sys-

tern as a whole, would account for 1500 feet of offshore resistant volcanic

bedrock being moved across the old mouth of the Pescadero Valley system in the

last 30,000 years since the last lowest mid-glacial low-sea-level valley-

cutting period. Marsh management must accommodate this rather unique "self-

damming" tidal inlet.

~·l· Hydrology

The wetlands system depends primarily upon Pescadero and Butane Creeks

for its supply of fresh water, while Honsinger and Bradley creeks and sur-

rounding hillsides are secondary contributors. Both primary sources are

perennial streams, although there is very little flow during the late summers

of extremely dry years. Ninety percent of Pescadero creek•s annual flow

occurs from December through April. Peak discharge typically occurs in Janu-

ary and February during heavy rains when the soil is saturated from previous

storms. Streamflow tends to respond rapidly to precipitation, due probably to

basin shape and storm orientation relative to basin, steep slopes, relatively

impermeable underlying soils, particular land-uses, and well-developed

drainage pattern. Correspondingly, these streams carry large quantities of

sediment. The physical and biological conditions in the marsh fluctuate

depending upon the dynamic interaction between fluvial and tidal conditions.

Draft Page 53

2.·1·1· ~ Base:

Much hydrologic data exist for Pescadero, although the quality of the

stream-flow records particularly leave much to be desired. For the purposes

of this management plan study, it was necessary to establish a history of

flood flows in order to estimate levels of flooding of the marsh area and sur­

roundings at various frequencies and magnitudes of flow, and was necessary to

estimate both past and future sediment transport regimes and transported

volumes of sediment entering the marsh/lagoon system. Since sufficient tidal

exchange is not present to allow flushing of much of the sediment delivered to

the tidal estuary, it was also necessary to model conditions of change that

have occurred in tidal exchange volumes through historic time.

The foregoing requirements demanded a more complete data base than was

available for this site. To develop the necessary information, it was there­

fore necessary to model and reconstruct past streamflow records on a detailed

daily basis, from which sediment transport models could be developed. For­

tunately, a number of sound analyses of regional hydrologic information appli­

cable to the Pescadero Marsh area have been completed before this study and

provided an analytical framework for testing new models. Earlier significant

works include the July, 1939, Preliminary Bridge Report prepared by the Cali­

fornia State Highway Dept. (1939) for the proposed Highway one Bridge; the

December, 1969, Interim survey Report by the Corps of Engineers (1969) on Pes­

cadero Creek wherein a series of flood control and water development projects

were proposed and analyzed for both Pescadero and Butane creeks; and the

April, 1982, san Mateo county Flood Insurance study (FEMA, 1982) outlining the

flood hazard areas in the Pescadero watershed in the vicinity of the marsh.

Other significant independent analyses of hydrology include the April, 1984,

Draft Page 54

Corps of Engineers letter-report (1984) to CalTrans on the hydrologic implica­

tions of proposed new bridge designs at the Highway one crossing site, and the

extensive analyses conducted by consultants to landowners and by CalTrans for

the 1984 legal action (Phipps vs state of california, op. cit.) which included

reports by Heyes (1979, 1981) and Simons (1984).

Precipitation records are available for a long period for the Pescadero

area. careful analysis for this report demonstrated that the record is of

very good, internally consistent quality. Most of the stations have not been

affected by urbanization or changes in station location. Those records of

greatest local value are as follows: Pigeon Point Lighthouse (1875-1944), Ano

Nuevo Lighthouse (1890-1945), San Gregorio 3SE (USWB #7807), Boulder Creek

Huhtala (1945-ff), Portola State Park (1945-ff), Boulder creek Locatelli,

Calif. Division of Forestry--Pescadero, Pescadero County Highway station,

Butano Falls Tract watermaster, La Honda, Black Mountain 25W, Ben Lomond,

santa Cruz, scarsdale Lake, saratoga Summit, and Skylonda. Some of these sta­

tions had, for at least short periods, recording gages to measure rainfall

intensity. Some, such as the two lighthouses, santa cruz, and Boulder creek

Locatelli, have very long period records. These were compared with the long­

period but lower quality records for san Francisco and Palo Alto to develop

synthetic long-period records for the Pescadero watershed itself. Precipita-

tion intensity analysis using the recording gages and other statistical

methods was done by the Corps of Engineers (1968) to conduct a unit-hydrograph

analysis for maximum intensity storms for their Pescadero Creek dam analysis.

The u.s. Geological survey (Rantz, 1971) conducted a regional analysis that

included this area for the u.s. Department of Housing and Urban Development.

Those two separate analyses, using the same data base but somewhat different

Draft Page 55

methods, are internally consistent. Most significantly, when updated with

current data, the earlier analyses have proven sound. A very complete

analysis of rainfall intensity associated with the January, 1982, storm has

largely verified the earlier work (U.S. Geol. survey, in preparation).

From the available record we learn that maximum runoff volumes do not

generally occur in years of maximum peak floods. Within a period of reason-

ably accurate records, maximum precipitation for a season appears to have

occurred in the water-years of 1868 and 1918. Within the period when both

precipitation and runoff records have been available, the peak annual runoff

occurred in 1941 with an estimated 84,800 ac-ft at the Pescadero Creek gaging

site, about 5.3 miles from the mouth. This would equate to a total watershed

volume 10 of about 144,000 ac-ft or 4.7 x 10 gallons. That is enough water to

cover the entire 320.33 acres of wetlands and potential wetlands to a water

depth of 450 feet. Minimum precipitation years result in minimum runoff

volumes. The year 1977 was the lowest of record with a maximum volume

delivered to the marsh areas of on the order of 1,200 acre feet. An estimated

volume about equal to that was removed from the streams for local irrigation.

Average annual watershed precipitation for the basinwide Pescadero basin

is estimated to be 39 inches (C of E, 1969). The 100-year 1-hour peak rain-

fall intensity is estimated to vary from 1.6 inches at the marsh site to 2.2

inches in the highest part of the watershed.

streamflow records are available within the basin for only two sites.

The best record is that for Pescadero Creek near Pescadero, which has been

gaged by the u.s. Geological survey since April, 1951. The station is 3.0

miles east of the town of Pescadero, 5.3 miles from the mouth, and records

runoff from 45.9 square miles of the 81.3 square-mile watershed. The other

Draft Page 56

station is Butane Creek near Pescadero, which was operated by the u.s. Geolog­

ical Survey from 1962 through 1973. It was located at a site just above the

"alder thicket," about 1.5 miles above Pescadero Road at the Preserve boun­

dary. The station platform is still in place, although much adjacent channel

alteration has occurred since it was abandoned. Both stations have a less­

than-adequate quality of gaging record. The sites are not well "controlled"

in terms of scour and fill associated with flood discharges, and thus errors

are introduced between each major storm and the succeeding flow rating. sta-

tion records indicate plugged conditions that persisted for critical winter

months and the stations were apparently not as well maintained as would be

desirable. By use of other nearby gage sites such as that near Half Moon Bay,

local records have been corrected for periods of missing record by the USGS.

However, for use in analysis for sediment transport, where accurate discharges

are needed on an hourly basis during changing storm conditions, the existing

record has proved almost worthless. The records are reasonably accurate for

estimation of values for monthly runoff, but peak and instantaneous values are

not always reliable. The data base for these published hydrologic data is

given separately after the References Cited in this report as Pescadero study

Hydrologic Bibliography.

For the purposes of this study, it was desirable to have a reasonably

accurate daily flow record for Pescadero and for Butane for 50 years. Since

the Pescadero record did not begin until April, 1951, and since the Butane

record was only available for a 12-year period, synthesis of the longer record

was necessary. such synthesis is regularly done by cross-correlation with

other gaged basins. The Corps of Engineers developed a synthetic flow record

extension beginning with the 1917 water year for Pescadero creek for their

Draft Page 57

analysis of water supply issues. Their analysis, for mean monthly runoff

only, is of only marginal value for this current analysis. we used the good

record available for the san Lorenzo River at the "Big Trees" station as well

as cross-correlations with streamflow on the other side of the santa Cruz

Mountains at saratoga, and in the Menlo Park-Palo Alto area to develop a syn-

thetic daily flow record beginning with the 1937 water year. This gave us

nearly the desired so-year record. Examples of summaries of portions of these

data are presented in Appendices 3 and 4.

While reasonably accurate correlations can be assured for monthly mean

runoff (correlation coefficients of 90 percent or greater for stations as far

away as Arroyo seco Creek at Soledad with a record back to the 1890's), daily

values are considerably more difficult. Different lag times, different storm

patterns, and different watershed shapes all contribute to considerable day-

to-day and hourly variations between stations even as close as those on Pes-

cadero and Butano creeks. For example, for the 12 years of overlapping record

for these two stations within the Pescadero watershed, only 73 percent of the

daily variation of one station could be predicted from the values of the

other. Much of this can be explained by the very different characters of the

two watersheds above the gaging station and the poor quality record. Although

both stations will peak within a few hours of each other with a 2-hour rain-

fall (8 hours for Pescadero, 5 hours for Butano), Butano is a steeper

watershed (about 150 ft/mi vs 110) and has a markedly higher ratio of water­

course length to drainage area (Butano = 14.1 mi/21.2 mi2; Pescadero = 19.1

·; .2) m~ 45.9 m~ . Butano•s watershed is primarily west-facing while Pescadero's

higher headwaters catch northwesterly storms directly.

Draft Page 58

We developed our synthetic record for Pescadero Creek for the period ~937

through ~951 using a weighted double linear regression analysis for the mutu-

ally overlapping period of ~95~ through 1960 for the san Lorenzo River sta-

tion, the saratoga Station, and the Pescadero creek station. The goodness of

fit was 94.10 percent, indicating an acceptable level of accuracy for the

prediction of daily values for the 15 years of missing record for Pescadero.

The much longer missing record for Butane was synthesized at a lower predic-

tive accuracy, based upon a single regression with san Lorenzo River for the

period of mutual record from 1962 through 1971 with an

goodness-of-fit.

From the streamflow analysis we learn that the peak discharge of record

occurred in December, ~955, when 9,420 cfs as gaged at the "near Pescadero"

gage equates to 14,500 cfs at Highway One. The peak flood of January, ~982

almost matched that of 1955 with 9400 cfs. This peak event of record is

estimated to be 3400 cfs for Butane creek at Pescadero Road where it enters

the Marsh. The additional 1600 cfs peak is derived from the area between the

two gaging stations. Five-day total runoff from the peak period of the ~955

flood was about 34,700 ac-ft, or enough to cover the complete wetland area

about 108 feet deep. The average annual flood volume for three consecutive

days of maximum storm flow is about 5200 ac-ft at the mouth. This equates to

an annual maximum average daily discharge at the mouth of about 875 cfs, and

is enough water to flood the 320 acres of the Preserve wetlands to a depth of

16 feet if the water were dammed in place.

The daily data show much more. Although the peak discharges of 1955 and

1982 are virtually identical, the ~982 conditions were much more sustained and

sediment transport was thus probably higher. In 1982 there were 30 days of

Draft Page 59

flow averaging greater than 500 cfs at the Pescadero gage. This flow condi-

tion equates to just over 1000 cfs at the mouth which is close to the minimum

discharge needed to exceed critical flow depths at the mouth and create back-

water conditions in the lagoon. Moreover, the 1982 season is dramatically

different than any other for the period of record. Critical and significant

flows were exceeded only 13 days in 1955, compared with the 30 day of 1982.

The next most significant years for sediment transport were 1940, 1937, and

1957, each with 18 days of greater than 500 cfs at the gage site. The years

1968 and 1951 also exceeded the 1955 record, with 16 and 15 days respectively,

and even 1981, immediately preceding 1982, had 12 days of erosive significant

flows. Thus, the 1982 year was by far the greatest of record for potential

bank erosion with sustained high flows, and 1982 saw the greatest number of

days of runoff-flooding of the marsh lands.

The average annual runoff at the Pescadero gage, for the full period of

flow records between 1951 and the end of the 1982 water-year is 29,920 ac-ft.

This equates to a runoff volume at the marsh of 50,864 ac-ft. This means that

the average year sees delivery of over 150 feet of water to the limited 320-

acre marsh/lagoon area. This also equates to an average annual year-long

discharge at the mouth of 70 cubic feet per second.

Use of the Pescadero gaging station site to estimate conditions in the

marsh is relatively simple and reasonably accurate for average or above-

average flow conditions. The necessary variables for equating runoff and peak

flow at the gage to that elsewhere in the basin are as follows: Mean Annual

Precipitation (MAP) in the basin above the gage is 42 inches for the 45.9 .2

m~

area. MAP for the entire watershed basin is 39 inches for 81.3 mi2 . For Wor-

ley Flat, upon which the Corps of Engineers conducted important hydrologic

Draft Page 60

analyses .2 (1968, App. A) MAP is 43 inches for an area of 37.5 m~ Total run-

off at the mouth, for example, is a function of the difference in catchment

area and average area-elevation weighted precipitation. Thus, a crude but

acceptable estimate of runoff at the mouth that it is equal to 1.7712 [area] x

runoff at gage, minus 7.143 percent [precipitation difference], This works

out to gaged runoff x 1.7. Similarly, Worley Flat is equivalent to gaged run-

off x 0.83. Runoff at the mouth =runoff at Worley Flat x 2.075. Peak flows

do not have the same relationships because of the differing lag and channel

conditions in Butane and Pescadero basins. Using existing records, we can

empirically determine that flood peaks for the mouth will be roughly

equivalent to 1.54 x those for the gage site. This discharge is, however, the

peak into the upper marsh from the two sub-basins. outflow through the tidal

outlet is very much a function of tide, storm, wave, and lagoon-level condi-

tions and cannot be considered as 1.54 times the gaged rate except under ebb-

tide open lagoon conditions with little water stored in the marshlands. such

unique conditions are probably very infrequently observed in nature. It is

thus reasonable to state that outlet flows can only be estimated from the gage

record for limited times of flood flows and even then estimates are only very

approximate.

Flood flows are important in that they transport the bulk of the sediment

and control lagoon flood heights and sediment flushing. By studying both pre-

cipitation records and runoff flood records, we can extend a record of years

of "significant" flooding back in time well beyond runoff records. We cannot,

however, rank those early floods or estimate their effects, except in cases

where geologic records of their earlier heights may be found. Approximately

33 flood events of an estimated discharge greater than 6000 cfs into the marsh

Draft Page 61

area are believed to have occurred. We know volumes accurately only for th~

period of the 1952 water year to the present when the Pescadero gage exists.

crude estimates of peak daily flows were prepared for this study back to 1937

based upon correlation with the San Lorenzo River, and even cruder estimates

could be made back to 1898 based upon the Arroyo seco flood record near

Soledad. For the purposes of the present study, it is really the sequence of

years of significant floods that is important. These are as follows: 1798-

99, 1819, 1849-50, 1852-53, 1861-62, 1867, 1871, 1874, 1878, 1879, 1881,

1889-90, Feb 1894, Jan 1895, Jan 1909, Jan 1911, Jan 1916, Feb 1919, Feb 1940,

Jan 1943, Dec 1952, (4030 cfs at gage), Dec 1955 (9420), Apr 1958 (7630), oct

1962 (4620), Jan/Feb 1963 (6200), Jan 1967 (4100), 1973 (5380), 1978 (4060),

and Dec 1982 (9400). several years such as 1982, 1881, and 1861-62 had

several flood peaks above the significant level. The years given are the

actual years during which flood conditions occurred, not the water years.

"Significant" floods are those thought to have been capable of carrying layers

of sediment into the lagoon that are preserved there today and capable of

extensive overbank flooding in the lagoon;marsh area which could change chan­

nel form or position if unconstrained by dikes.

Tide ~ ~ data for Pescadero are not of high quality. The published

tide tables for san Francisco, with their appropriate corrections for the Half

Moon Bay area are simply predictions of mean values. These data are available

for all years beginning in the 1880's, through u.s. Dept. of commerce and

Labor, coast and Geodetic survey, annual tide tables. They are published one

to two years in advance of the year for which the data are applicable. The

published data are for differences from a MLLW (mean lower-low water) datum,

which at san Francisco is 3.0 ft below mean sea level. At Pescadero, it is

Draft Page 62

estimated to be 2.6 feet below mean sea level with an additional 0.3 ft

regional correction to be added to that for high tides only, yielding a net

difference between local Pescadero mean sea level at high tides and the pub­

lished san Francisco tables of +2.9 ft. The published value is thus 2.9 feet

higher than the prediced numerically-determined mean sea level expected for

Pescadero. In fact, using the tide tables as carefully as possible with accu­

rate curves to interpolate between maxima and minima, it was found that tidal

levels for the period of careful observation at Pescadero in 1983 and 1984

were seldom within a few tenths of feet of that predicted. Storm conditions

were associated frequently with tidal levels 2 or more feet different than

those predicted. The mean values of observations during non-storm times gen­

erally exceeded those levels prediced by at least 0.3 ft. Some of this dif­

ferential may be due to net compaction of the two primary benchmarks, which

are both on unconsolidated soft sediments.

wave climate data applicable to Pescadero, upon which estimates of wave

run-up and beach profile could be estimated, were available only from 1980 to

the present and could not be used for historical analysis. Storm wave condi­

tions could better be estimated historically from newspaper and other pub­

lished records. These are the data summarized by Griggs (unpublished) for the

period 1910 through 1982.

survey data for elevations with the marsh/lagoon areas were largely com­

piled for this report through original field work. Some data are available

from ca1Trans who have produced a detailed carefully controlled topographic

base map of the mouthjbeach area based upon aerial surveys of 6-23-so. Those

records also permit establishment of control elevations and positions along

Highway one from the Pescadero Road turnoff to North Pond, and include control

Draft Page 63

bench marks on the rocky point and in the various parking lots south of the

bridge. san Mateo county Public Works records of bridge construction provided

control elevations on their two Pescadero Road bridges in the vicinity of the

townsite, over Butane and Pescadero creeks. A u.s. Geological survey bench-

mark on the Butane creek Pescadero Road bridge at the Preserve boundary pro-

vided primary control in the upper marsh area (elev. 12.828 ft rnsl), while the

CalTrans bench mark in the northwest Highway one abutment (31.14 ft rnsl) pro-

vided primary control to the west. Both sites were intertied through level

surveys across the marsh. A secondary pin in the center of the Pescadero Road

where it joins Highway One at 47.47 ft msl was used as an added check point.

Important general elevation data include the following: North Point sur-

face, July 21, 1984 = 5.7 ft rnsl; North marsh at its low pump site= 5.6;

North marsh at higher east end = 6.6; Delta marsh at junction of Pescadero and

Butane creeks-water surface and sediment level= 6.1; Delta marsh at end of

dike remnant extending from Round Hill= 7.5; north extremity of left-bank

Butane creek dike enclosing North Butane marsh, dike top= 9.7; Phipps tide -~----~'"~'

gate, top of_hinge-pivot = 1.3:8. In general, dikes have limiting low-point -------·

elevations of about 9-9.5 ft (except where breached). Marsh lands are found

at elevations of 5.6 feet to ±10 ft. Below 5.6 feet there are only tidal mud

flats or tidally flooded channels. Floating debris is concentrated most at an

elevation of about 6.2 ft but extends to 10.0 or ___ ft around the marsh area.

An important series of survey profiles were made in the vicinity of the

river mouth at tidewater. A bench mark pin on bedrock along the left bank at

the position of the cut for the old haul road used to construct the Highway

one bridge, just downstream from the bridge, is 4.463 ft rnsl. The tops of

rocks exposed in the stream bed at the site of the bend 300 feet below the

Draft Page 64

bridge are at +0.76 ft, the tunnel floor is at -0.31 ft at its upper end, and

the roof of the tunnel is at 10.06 ft. The bedrock bed of the stream channel

when defined at low tides 450 feet below the bridge near the end of the north­

ernmost rocks at the rocky point is between -2.45 and -2.37 ft. The slope of

the outlet stream water surface at low tide with tidal outflow between the

bridge and the bedrock control 300 ft downstream is 0.0037.

The hydrologic data base was used to assess 4 basic areas of management

concern. These include 1} floods generated by runoff; 2} sediment transport

into the marsh/lagoon; 3} tidal exchange and breakout floods; and 4} dike

management. Discussion of these subject areas will be limited to those ana-

lyses and factors directly influencing management decisions or options

thereof.

a} Runoff Flooding - frequency~ frequency duration: Appendix 3 is an

analysis of annual maximum flood discharges for the Pescadero-near­

Pescadero gaging station. It is primarily useful for assessing the

recurrence frequency of large magnitude floods. The lower magnitude

values for dry years are "mis-weighted" by the data point for the 1951

water-year which did not include the highest flows of that year since the

record did not begin until after the winter maxima. From the actual

record we can estimate, using this Log-Pearson Type III frequency

analysis, that the 100-year flood volume at the coast is approximately

22,000 cfs (14100 at the gage x 1.54}. This compares with an estimate of

24,000 cfs by the corps of Engineers (1969) as adopted by FEMA (1982}.

we can see that the 1982 and 1955 instantaneous flood peaks were

Draft Page 65

approximately 20-year events (14,500-15,000 cfs at the coast), and that

the average annual flood peak (2-year RI) is approximately 2600 cfs at

the coast.

More important for management decisions is the frequency-duration

analysis. The analysis conducted by the c of E in 1969 for their worley Flats

darnsite (37.5 mi2 ) provided a published curve that could be interpreted for

the marsh area. Their plate A-9, Appendix A (1969), shows that the average

5-day flow that is exceeded every other year is about 6400 ac-ft at the marsh

(3,100 x 2.075). The 100-year 1-day flow volume will be about 31,000 ac-ft,

with a 5-day flow of 68,000 ac-ft.

step-backwater analyses of runoff flooding: Flood heights for vari-

ous discharges can be calculated for the marsh area. This is most readily

accomplished with what is called a backwater calculation, based upon hydraulic

characterist;;.;:;::; a limiting downstream point and "back-calculating" for

flood heights at respective upstream points. Backwater calculations were

first performed for the design of the original Highway One bridge (Brummel,

1939). In that report a non-conservative estimate of 10,000 cfs was used as

the assumed 100-year discharge for the mouth of Pescadero creek at the estuary

outlet, and from that a calculated height of flooding in the lagoon/marsh of

8.5 feet for the 100-year event was estimated, in accord with their belief at

that time that agricultural properties were protected by levees to that eleva-

tion. The calculations and assumptions of 1939 have been important for the

marsh area. Although the estimate of the 100-year discharge magnitude was in

error, the other presumptions upon which bridge design was based are very

informative.

Draft Page 66

The highway hydraulic engineers assessed correctly that the height

of the blocking sand bar in calm summer conditions was about 6.0 feet. They

estimated that winter open-bar conditions would still effect resistance to

outflow of Pescadero creek to elevations that they guessed to be about 1-foot

above the sand bar height, or 7.8 feet. Although the reasoning was not

entirely sound, the resulting height of high storm tides in winter is about

correct at 7 feet. The Federal Emergency Management Agency study (FEMA, 1982)

used the 1969 Corps of Engineers total 100-year flood peak estimate of 24,000

at the mouth to conduct a backwater analysis for floodplain delimitation.

Then in 1984, the Corps of Engineers, using the FEMA data on the channels and

marsh dimensions, calculated backwater elevations for the marsh area (Wisney,

1984; Angeloni, 1984) substituting differing bridge design options to assess

their effects upon the marsh area. In all of these cases, the critical vari­

ables depend completely upon the characteristics of the mouth of the river and

its tidal interactions. Basic assumptions were, in every case, that resis­

tance to flow at the mouth was effective at elevations of +1.0 to -6.8 feet.

As the FEMA bedrock streambed profile shows, scour below -0.8 ft msl is impos-

sible. Although the FEMA study is based upon real surveyed elevations of the

streambed, the elevations of effective tidal resistance are not apparently

included in the analyses. Even the 1939 study, despite narrative discussion

of +7 foot resistance, used an elevation of mean sea level for their actual

channel-bottom, no-resistance, calculations. It is thus the empirical data

that may be the most important for analysis for management of the marsh/lagoon

system.

The empirical data base is marginal. During the two years of care­

ful monitoring of water levels in the lagoon for this study, there were no

Draft Page 67

significant runoff floods. A 1983 storm tide maximum of 6.6 to 6.9 feet above

mean sea level resulted in the highest lagoon stands during a time of an open

bar. In 1984 the seasonal open tidal maximum elevation was +6.4 ft msl.

These two events occurred in autumn without significant runoff. The flooding

of the winter of 1939-40 was observed to have caused scour of 7-8 feet below

the pre-construction streambed of August, 1939, when that site was resurveyed

in June of 1940. However, we do not know the 1940 peak discharge, nor the

maximum lagoon surface elevation for that year of great runoff. The scour was

measured at the site of ongoing construction of bridge piers in unconsolidated

sand and could have simply been the result of locally changed conditions. The

1955 flood, with an estimated discharge at the mouth fo 14,500 cfs, based upon

the gaged record flood of 9420 cfs, is fortunately associated with a lagoon

flood height, marked shortly thereafter on the upstream end of the south High­

way One Bridge pier. That elevation was 9.37 feet msl, as surveyed from the

old paint mark for this present study.

Tidal conditions are not known for the time of the 1955 flood peak.

Howeer, using the surveyed outlet channel dimensions and the 1955 lagoon

level, we can calculate a step-backwater regression to determine how the

outlet channel controls the lagoon levels. By a series of approximations, we

estimate that the primary control point at the outlet is the stream bed eleva­

tion approximately 300 feet below the bridge, and 200 feet above the low-tide

outer limit of a defined stream channel. At this point of control, the effec­

tive base of the flow is at an elevation of +0.32 ft msl. The actual surveyed

maximum elevations of the tops of rocks in the channel is +0.76 ft msl. In

1955 the critical depth at this site is calculated to be 6.5 feet, with a

discharge of 14,500 cfs through an effective area of 1144 ft2 with a roughness

Draft Page 68

factor (Manning's n) of 0.08 in the rocky surf zone. These conditions result

in an elevation of 9.37 ft on the upstream bridge abutment. such calculations

are approximate only, but do serve to show us that scour below sea level could

not have occurred in 1955 at the outlet, and we know that such cannot occur

today because of the bedrock channel floor. we can also see that storm tides

did not seriously interfere with streamflow in 1955 at the peak lagoon levels.

The significance of the analyses of both the empirical and theoreti­

cal flood heights for management is profound. It is not possible for the

outlet stream today to scour seaward to any significant depth. we know from

peak flood observations at other coastal lagoon outlets that scour occurs well

below sea level where not constricted by bedrock (San Lorenzo, Golden Gate,

and Bolinas lagoon outlets are examples of sites of such scour). The FEMA

flood maps for the lagoon;marsh area are accurate from the bridge-site

upstream because they are based upon the assumption that scour does not occur

at the mouth. That assumption is verified by the analysis of the 1955 situa-

tion. FEMA's analysis shows that the narrow point spanned by the highway

bridge effectively determines flood elevations upstream completely across the

state Preserve lands. Their analysis shows that the 100-year backwater will

be just under +15 ft msl just above the bridge, rising to about 15.2 ft along

the eastern Preserve boundaries (8940 ft above the mouth). Since tidal condi­

tions in 1955 are not known, and since the controlling bedrock outlet is

slightly above sea level, the most reasonable conservative flood elevations

should be those based upon the Corps• newer (1984) analysis of the FEMA

cross-sections, for conditions of "shoaling" to 1.0 to 1.5 feet. Their

analysis for shoaling to +1 foot msl indicates 16.18 feet at the bridge and

16.9 feet at the Preserve border (Angeloni, 1984).

Draft Page 69

b). Sediment transport: A study of management alternatives in a site impacted

by high sedimentation rates demands good data on actual sediment tran­

sport. Unfortunately, sediment transport is not a linear function of

streamflow, and one cannot readily estimate high-flow transport rate con­

ditions from observation of low flow volumes. In this study, late fund­

ing resulted in missed opportunities to sample high enough flows to

reflect conditions during significant transport events. Most years are

not characterized by flow conditions associated with the transport of

most of the sediment. It is the 10-year flow events or greater that move

over 80 percent of the sediment volume. To compensate for sediment tran­

sport observations that were restricted to events less than even average

annual flood peaks for the instrumented observation periods of 1983 and

1984, sediment transport modeling became necessary. Two modeling stra­

tegies provided usable data.

Using observed transport rates at lower flows to calibrate mathemat­

ical sediments transport equations derived from empirical observations in

other streams worldwide, it was possible to estimate total volumes of

sediment that could be transported for all the synthesized and real aver-

age daily streamflow levels for the modeling period of 1937-1982. This

method was verified at the Carmel River, California (Curry and Kondolf,

1983), This method valid only so long as the streams are not "sediment

limited"; that is, so long as more sediment is available to be moved in

contact with flowing water than the flow is theoretically capable of mov­

ing. An alternative modeling method, used as a check against the

beforementioned theoretical method, is to simply estimate the direct

volume of sediment deposited in the marsh area, and eroded in the source

Draft Page 70

areas, to crudely estimate net sediment flux. Here, again, one must use

real empirical data on grain sizes available for transport to compare

with those seen in deposits, to estimate the volume that may have been

carried out to sea as suspended sediment.

Sampled sediment transport rates were limited by observational

opportunities and equipment to flows only to 36 cfs on Butano and about

2x that on Pescadero. Highest transport rates by far were observed on

the Butano where, with a water depth of only 8.6 ft, approximately 500

ft3/day were transmitted as bedload. suspended load at these low flows

was negligible. In the Butano basin, the average size of the material

transmitted onto state Preserve lands is 0.6 mm. Eighty-two percent of

the bed sediment (bed load) is medium to fine sand between 0.125 and 1,0

mm median diameter. Less than two-tenths of one percent is silt size

(0.125 mm) or smaller, although the material stored in the stream-banks

undergoing active bank erosion upstream comprise some 30 percent

siltjclay size material. Thus, we must conclude that at least an addi­

tional 30 percent is being moved as suspended load at higher flows. Pes­

cadero sediment transport was simply not observed at measured discharges

owing to bed armoring that does not exist on Butano Creek. Theory

predicts bedload transport initiation on Pescadero Creek at between 100

and 200 cfs.

Using synthesized and real daily flow records and empirical data on

sediment sizes available to be moved, sizes actually moved, water depths

in real channels, and real surveyed stream transport gradients, it was

possible to crudely estimate past sediment transport capacity for Butano

creek, which is not limited to its lower course by available sediment.

Draft Page 71

From about the position of the mountain front along the easternmost trac&

of the San Gregorio-Hosgri fault, Butano channels are not armored with

cobbles in low flow times. Thus, sediment continues to be transported

even down to the lowest threshold velocities and discharges that could be

measured of a fractional cubic foot per second. Pescadero Creek, in con­

trast, is armored over a major portion of its channel downstream to the

Round Hill vicinity, and bed sediment transport stops abruptly on falling

flood hydrographs in a matter of hours to days after cessation of storms.

In Butano, even falling tides were noted to moved bedload.

suspended sediment data are available for some higher flows for Pes­

cadero Creek, but none for Butano. Based upon the sampling done in the

marsh and lagoon areas, it is believed that most channelized flows carry

suspended sediments out to sea and that it is not presently creating

problems in the marsh area. However, with reopening of diked-lands to

regular flooding, these finer-grained, nutrient-rich, sediment fractions

will again become part of the depositional environment of the marshlands.

Using data derived by sampling headwater areas for this management

study, and using published sediment-yield data for the western Santa Cruz

mountains (particularly san Francisquito creek), we estimate that the

current background sediment yield rate for upland areas of the Pescadero

watershed has been approximately o.s ac-ft/yr/mi2 for the past 30 years.

This figure is based upon the logging history during that period (see

Fig. 7), and is consistent with the analysis done by the Corps for their

1968 dam design (C of E, App. A, p. 22 ff). The Corps' conservative

design rate was 1.0 ac-ft/yr/mi2 at a time of higher logging-related sed-

iment yield rates. There is no question, based upon many studies of

Draft Page 72

logging-related sediment yields, that the period of the late 1800's would

have been characterized by much higher over sediment yields (see

Bergquist, 1978, p. 169). At Bolinas lagoon, logging increased sediment

yields approximately 4-fold in the 1800's.

Using the o.s ac-ft/Yr/mi2 estimated long-term average sediment

yield rate to estimate background levels, we find that the 53.5 sq mi o£

Pescadero creek upland would yield, in the last 30 years, aoz ac-ft o£

sediment. The Butane uplands would similarly yield 330 ac-ft. Eroded

sediment from the lower alluvial channels can be estimated from the

aerial photos for the same period of time. We estimated that the 3.5 mi

of severely disturbed incised Butane channel above the alder thicket lost

about 1700 ac-ft, while Pescadero may have lost on the order of 500 ac-ft

in the 30-year period beginning with the 1955 flood and extending through

the current season. Subtracting 30 percent for silt-clay size material

that existed in the source materials but was not deposited in the marsh

area, we estimate about 1420 ac-ft of sediments yielded to the lower

basin by Butane and about 910 for Pescadero in the last 30 years.

Core sampling in the marsh, lagoon, and channels has provided a

rough estimate of thicknesses of deposited sediments following major

area-wide flood events such as that of 1955. Although there is no cer­

tainty that simple estimation of sequences of flood deposits in shallow

hand cores is capable of identifying each post-flood sequence at each

sampling site, general ideas of depth of sediments accumulate s~nce ±1955

was possible in a number of sites. Areas of agricultural use could not

be sampled accurately, but lines of equal thickness of sediment units

could be projected from adjacent less-disturbed areas. Deepest

Draft Page 73

sedimentation was found in the alder-thicket area where 6 feet minimum

characterized the sites that are not current channels. Lower areas of

overbank flooding associated primarily with Butano Creek sources (Butano

marshes and most of the Delta marshes) had 2-3 feet of post 1955? sedi-

mentation. Pescadero depositional areas (North marshes, Round Hill

field, etc.) had very much less sediment accumulation. Thus Pescadero

sedimentation was discontinuous and varied from less than 1 foot near the

beach to on the order of 2 feet near the eastern edge of the Preserve.

Although the marsh area is one of common deposition from all sources

including long-shore drift, dune sands, and the two primary tributaries,

one can determine which areas are dominated by sediment from the various

sources. Much effort was expended attempting to differentiate between

Pescadero and Butano sources in sediments. Lithologically, the two

source areas are virtually identical. Minor differences were insuffi­

cient for source differentiation, especially since we believe that a sig­

nificant portion of the Pescadero alluvial fill is, in fact, of Butano

origin, along the eastern traces of the san Gregorio-Hosgri fault. The

remaining tool for estimating source of a sediment is simple topography.

The 2-foot to 5-foot contour interval maps available through san Mateo

county and CalTrans proved more than adequate for determination of gra­

dients away from source channels. These maps can only reveal conditions

at the times of their aerial-photo base information, but these were con­

sistent through the 1960's and 1970's. Based upon topographic gradients,

Butane sediments dominate approximately 285 depositional acres, and Pes­

cadero dominates at most 189 acres. These depositional sites include the

alder thicket and the natural overbank agricultural areas between the

Draft Page 74

town of Pescadero and the marsh area.

Average Pescadero sediment thickness, although quite variable, since

December, 1955, are 2 feet or less, while those of Butane are about 5

feet. Comparing the estimated sediment yields of the sub-basins in the

last 30 years with the empirically estimated deposition, reveals that

virtually all of Butane's sand-size sediments are trapped in the marsh or

other depositional areas, while about 60 percent of the same grain-size

fractions in the Pescadero channel must exit to the sea. In other words,

1420 ac-ft of Butane sediment, distributed over 285 acres, yields very

close to the estimated 5-feet average decomposition. But Pescadero's 910

ac-ft of sediment should also equal nearly 5 feet of accumulation of

bulked sediment, yet at most only 2 feet can be accounted for in terres­

trial sites.

The theoretical sediment transport capacity of the two tributaries,

where calculated for the channels as they enter the Preserve lands, is

entirely consistent with the empirically estimated sediment flux. The

sediment transport equations do not prove that the required amounts of

sediment were actually transported, only that, if available to the

streams, these are the correct orders of magnitude of sediment transport.

Thus, in summary, the sediment yield analysis indicates that the two tri­

butaries behave quite differently. Pescadero Creek has a sufficient gra­

dient in its lower course to carry the bulk of its load to the beach to

nourish the beach and sand dunes. Probably because of that steeper gra­

dient, Pescadero creek is armored with coarser sediments in such a

fashion that low flows between storms do not carry bedload sediment.

Butane, on the other hand, has such a low gradient lower 3-mile stream

Draft Page 75

course that it cannot transport its load to the sea. Further, its una~­

mored lower stream bed and fine to medium sand bed provide opportunities

to move minor amounts of bed sediment even at mid-summer base-flow condi­

tions. Most of the bed-load portion of Butane's sediment is trapped in

the lowlands and is not discharged to the beach. The average sediment

yield from the Butano basin at about 3.06 ac-ft;yrjmi2 is about 4 times

that for Pescadero basin for the last 30 years.

c). Tidal exchange and breakout floods: Pescadero lagoon;estuary has so lit­

tle tidal exchange at present that its study is relatively simple. At

times of highest observed tides (+6 ft msl, +6.6 ft MLLW tide-table

datum) all of the active stream channels of the Pescadero area are tidal.

Tidal effects along Butano Creek reach the Pescadero Road bridge at a

lagoon-stage of about 4.60 ft msl, which are usually reached on two or

more occasions a year. At this stage, tides reach up Pescadero's channel

to the approximate location of the hill east of Round Hill, at an old

pump site in the eucalyptus north of the old ranch buildings. When the

bar is closed across the mouth and high tides coincide with short-period

steep waves to fill the lagoon to higher levels, all of the area shown on

the 1854 map as marsh may come under the influence of saline waters. The

1854 surface area became wetland in November, 1963, at lagoon levels of

6.6 to 6.9 feet msl, and again in september of 1984, with precipitation

coupled with lagoon levels to 5.9 ft msl.

If, for the same of modeling, we take the volume of water contained

at a +5 to +6 foot msl tide with an open bar as 300 ac-ft, which is a

reasonable maximum based upon topography assuming dikes are not hindering

passage of water, then we can propose an average outflow for 6 hours of

Draft Page 76

ebb conditions at 605 cfs. Peak flows would be on the order of 1000 cfs

which, in theory, are just enough to exceed critical flow velocity and do

significant erosive work at the mouth. This assumes the present observed

6-hour tidal lag between the coast and the uppermost reaches of tidal

influence. Today•s small estuary volume also drains in about 6 hours,

but its maximum tidal discharge is only about 400 cfs. Today's volume of

tidal exchange is estimated to be about 55 ac-ft, all restricted to the

small estuary and two channels at peak tide stages. The area of today•s

estuary is less than one-half that of 1900, according to Violis (54.1%

reduction 1900-1960; Violis, 1979), and its volume reduction due to dik­

ing and sedimentation combined may be on the order of one-tenth--but is

unknown. From a management standpoint, there is little that can be done

about the accumulated sediment, but we can increase the exchangeable

volume from 55 to 300 ac-ft.

About the only empirical evidence we can gain for what would be the

normal operating conditions of tidal exchange in an undiked area is that

to be gained from observation of the draining of the marsh upon breakout.

Artificial opening of the bar at times of little excess runoff but high

lagoon stage gives an opportunity to judge rates of discharge and

drainage times. Every artificial breakout is different. some occur dur­

ing high tides and, as apparently occurred during at least one attempted

opening in 1977, may result in adding more water to the lagoon. Others

occur at times of high rainfall when discharge is augmented by precipita­

tion. Beach width very much affects the development of an outlet channel

upon breaching, as does the site chosen for the breaching. Thus, as may

be expected, estimations of discharge at the mouth based upon observa-

Draft Page 77

tions of rate of dropping of lagoon levels vary widely. D. Heyes of Cal­

Trans (personal communication) observed a drop from 6.0 ft to 4.5 ft in

40 hours in the 1977 drought period, with no significant runoff or pre-

cipitation. Several tidal changes would have occurred during that 40-

hour period so discharges may have even been negative at some times.

Tommy Phipps (personal communication) reports occasions of drops of 6-8

feet in a 12-hour period. From the Phipps tide gate base at about a

stage of 7 ft, this observation would equate to something like an average

of 55 cfs for the full period of falling tide. This is a reasonable

number for full drainage. No such conditions have been observed in the

course of this management study. our highest discharge reading upon

opening of the bar occurred 11-19-83 with a peak discharge of 400 cfs on

a drop in stage of 1-foot between successive tides at a stage of 4.0

feet. This was augmented by storm runoff.

The basic character of the draining marsh/lagoon system today is one of

very slow (7-10 day) drainage of the diked lands with more rapid (12-24 hour)

draining of the actual small lagoon residual and its channels. To drain the

marshland areas within a 12-hour falling tide period will logically require

that the waters within those areas be able to enter the channels during a 6-

hour period (to accommodate the added 6-r lag). Dike modifications should be

accomplished to this effect. Thus, the limiting elements for tidal exchange

rate will be rate of falling tide and size of the river-mouth opening. We

have calculated that approximately 1000 cfs is needed at the Highway One

bridge constriction to generate any backwater from that alone. Thus, the only

variable that can be directly affected by management is the character of the

breakout channel. Wide unobstructed breakout channels will normally occur

Draft Page 78

most often with a naturally high lagoon level, a falling tide, and a moderat8

runoff flood volume. This will crate and maintain a breakout channel width of

on the order of 250 feet that will not readily be closed by longshore drift

immediately.

In summary, the tidal volume exchanged today is very small, often

insignificant. The only significant emulation of pre-diking tidal exchange

occurs on rare occasions with breakout floods, and those are believed to be

best encouraged by allowing natural breakouts only. With restoration of

twice-daily tidal access to all of the marshlands through dike modification, a

twice-annual maximum tidal flood volume and rate approximately equivalent to

today•s maximum breakout floods may be restored. Such a tidal exchange would

have a significant effect to help prevent progressive year-to-year accumula­

tions of sediment at the mouth from all sources, including the significant but

unknown contributions of the overwash deltas in the area of the Highway One

bridge. The healthy marsh/lagoon/estuary system is one with both breakout

floods and tidal exchange to do the job of flushing sediments seaward. The

present system is constrained by dikes, albeit breached, that do not allow

sufficiently fast filling or draining within a 12-hour tidal cycle. Sedimen­

tation has additionally restricted tidal exchange.

~·i· Modifications of the Natural Habitat

It is nece$sary to reconstruct the history of Pescadero Marsh to estab­

lish a model for restoration, and to define those processes responsible for

its evolution and subsequently predict the nature of its future. Pescadero

Marsh can reasonably be assumed to have existed as a drowned Pleistocene coa­

stal valley for millenia. Human-use and cultural history in the watershed

Draft Page 79

dates back centuries, while precipitation and runoff have been recorded fo~

mere decades. Long-term data on erosion and sedimentation are essentially

non-existent. Under the constraints of an inadequate data base, any attempt

to define the processes affecting the Pescadero Marsh's character and condi­

tion, demands the development and utilization of a set of techniques more

inclusive than numerical modeling. Among these alternatives are:

(1) synthesizing a data base by correlation with an analogous watershed;

(2) using vegetation as an indicator of modified conditions by determining

changes in vegetative patterns resulting from habitat

progression/regression and species migration/invasion.

interpreting geomorphic features as manifestations of processes occurring

within the watershed, while stratigraphy can indicate past events and

trends in sediment processes

To a limited extent these techniques can provide data capable of generating

quantitative first order approximations.

Maps and aerial photography can be valuable aids in such investigations.

Fortunately, aerial photographs of the Pescadero Marsh area are available

spanning over 50 years and provide the most valuable resource for assessing

recent human-induced environmental changes. The 1854 map provides the earli­

est documentation of the marsh's prior condition depicting the extent of

marshlands at that time, as is useful as well for determining the extent of

tidal influence (Figure 1).

However, using aerial photos for analyses of changes and trends is com­

plicated by variations in precipitation and runoff, tides, currents and winds,

seasons, and stream discharge into the ocean which obfuscate changes in the

Draft Page so

dependent variable of interest, namely sediment deposition and lagoon storag~.

Despite this, maps and aerial photography have been invaluable in determining

changes in sediment sources, land use patterns and practices, drainage and

channel morphology, beach size, slope and streambank stability, vegetative

patterns, and construction and development which can in turn be interpreted to

deduce processes operating within the watershed.

2·2· ~-Use History

Unique among coastal valleys, land-use patterns in the Pescadero creek

watershed have not changed dramatically during the past century. Timber-

harvesting, agriculture, livestock grazing, and tourism have been and remain

the occupation of time and land here. Accordingly, alterations in the charac-

ter and condition of the marsh are not easily explained by reference to such

causes as urbanization and development, or other instances of dramatic shifts

in land-use patterns. However, the cumulative effects of decades of such

practices throughout the watershed have undoubtaQly had an influence upon the

character and condition of the marsh. As a result of the marsh's position

downstream of all events and activities occurring throughout the watershed, it

is particularly vulnerable),to pot only dramatic modifications, but also incre-/ \, ·,._

mental alterations occurring across a long span of time or large area of the

watershed.

Man is a geologic agent. Some of our activities create unwanted events

or vastly accelerate natural processes. we erode the soil, cause landslides,

trigger earthquakes, alter surface and subsurface water flows, and affect

natural processes in many other ways.

Draft Page 81"

~·~·!· Modifications of wetlands

The primary human modifications of the wetlands are covered well by

Violis in his thesis on the area (1979). Only new data will be summarized

here. Violis documents the progressive reduction in uncultivated wetlands,

with the greatest reduction occurring between 1930 and 1968 (29 percent), He

also outlines the progressive diminution in size of the lagoon/estuary with a

47 percent reduction between 1930 and 1960 and a 54 percent reduction since

the end of the last century. Our work suggests that sediment influx contri­

buted strongly to the reduction in tidal areas as well as "land reclamation"

for agricultural purposes. The sediment influxes were primarily episodic and

associated with major storms and periods of watershed manipulation. Based

upon a sediment record that has only been outlined from 1955 to the present,

it is reasonable to assume that significant sediment influx occurred in the

period from the late 1850's through 1890 when major runoff floods coincided

with initial logging. Then the storms of 1940, 1956, 1958 and 1973 water-

years set the stage for the very long-duration floods of 1982 to carry the

bulk of the sediment to the marsh that we see within the top 6 feet of silt to

coarse sand.

significant channelization, particularly of Butano Creek prior to 1929,

destroyed the natural 3-channel distributory pattern of that sediment-laden

watercourse. Sediments originally distributed rather evenly over the Delta­

marsh were often then confined to a single long aggrading channel, and their

deposition was concentrated closer to the mouth. This additional sediment

burden at the mouth occurred at a time that coincided with 1940 construction

of Highway One. The site of the bridge itself was one of reduction of water­

course width by about 20 percent from 1928 to 1956 based upon aerial photos of

Draft Page 82

those years. The reduction in apparent watercourse width apparently resulted

from changes in sediment flux around the bridge, caused in part by the block­

age of the North Pond overwash area by the Highway One berm. Although the

bridge piers, and the scour associated with them in the 1955 floods, doubtless

contribute to a narrowing of the apparent watercourse width (a deeper channel

needs to be less wide), the most significant change in beach sediment circula­

tion was caused by the highway berm which increases longshore transport of

sand into the mouth of the estuary/lagoon.

Changes in vegetative cover on the coastal dunes has also reduced the

ability of beach sands to move out of the coastal beach circulation cells,

thus further impeding drainage of marshlands and increasing sedimentation

within the Preserve area. Finally, the human construction of the artificial

tunnel at the mouth of the outlet stream and the agriculturally-motivated

artificial opening of the beach bar have together reduced the frequency of

larger beach-modifying delta-eroding breakout floods, thus further contribut­

ing to the unnatural constriction of sediment movement passed the delta. Pes­

cadero Creek with its channel modifications tending toward straighter,

steeper-gradient courses compare dramatically with the diking of both sides of

Butane Creek and the tortuous course it must now take to the delta.

The wetland area depicted on the 1854 map (excluding open estuary and

channels) was approximately 298.9 acres. Today•s Preserve boundaries enclose

282.4 of those potential marshland acres. Despite accumulations of between 1

and 6 feet of sediment in the last 30 years in the marshlands, most of these

282.4 acres are still accessible to annual high tides at least one time per

year. Only about 19.5 acres have been "lost" to tidal influence since 1854 in

natural levees and dikes.

Draft Page 83

~·~·~· Timber-Harvesting

Activities related to the logging of timber lands can have a noticeably

large and immediate impact on the environment of forest lands and downstream

reaches of the watershed. Such activities may result in short-term erosion

and sedimentation far in excess of that which would occur under most natural

circumstances which may produce delayed effects of significant consequence

upon downstream locales. The impacts of timber harvesting derive not so much

from the sudden absence of vegetative cover as from the means by which the Y..) ,. J>. . )

timber is removed. Besides the elimination of protective elements, the pri-

mary impacts of logging operations include soil compaction and displacement,

and alteration of hillslope drainage. The excavation and exposure of surfi-

cial geologic materials during road construction, log skidding, and other log-

ging operations commonly results in increased runoff, landsliding, and erosion

of unstable soils and rock masses, and altered hydrologic regimens. The ulti-

mate effects of such activities upon downstream reaches are elevated flood

peaks due to increased and accelerated runoff, and increases in sediment flux

due to soil disturbance and the increased competence of runoff.

Although, the impacts of timber harvesting on forest land depend on

pedologic and geologic characteristics, the steepness of the topography, and

climate; equally critical if not more so are yarding methods, percent of trees

harvested, type of equipment used, road construction, location of landings and

skid trails, and care of operation. Accordingly, it is essential to not only

determine regions appropriate for harvesting, but to also define appropriate

harvesting methods. This responsibility lies within the California Department

of Forestry (CDF). However, their interests are state interests and tend to

generalize watershed needs. The unique and sensitive habitat of a coastal

Draft Page 84

wetlands requires special consideration.

It is important to appreciate that our mapping of timber harvest history

begins with the charted record. The major logging of the 1800's, covered in

impart in Violis' thesis (op. cit.), has certainly also been significant. The

work of Bergquist (1978) shows that, at Bolinas Lagoon, logging effects not

only resulted in an increase of over 4 times in sedimentation rates, but also

resulted in an influx of significantly coarser sediment. Although Bolinas

Lagoon is a very different kind of system than that of Pescadero, the rates of

sediment accumulation Bergquist found there for his post-logging period are ,>

comparable to those associated with Pescadero creek itself as it enters the

delta marsh area. One cannot assume, however, that logging in the 1800's sig­

nificantly filled the North Marsh area because the maps show this not to be

the case and gradients are too steep.

~·~·l· Timber-Harvesting History

A comprehensive history of timber harvesting in the Pescadero Creek

watershed has never been catalogued, and records are not available by which to

compile such a history. However, a number of resources are available from

which to derive at least a cursory view of recent logging patterns.

Since few stands of old growth redwoods exist in the watershed outside of

publicly-owned lands (county and state parks), it is apparent that most of the

watershed previously vegetated by redwoods has been logged at least once since

logging activity commenced in the area during the 1850's. More detailed

information of timber-harvesting patterns has been derived from a collection

of aerial photographs dating from 1941 to 1982, and from California Department

of Forestry records which date back to 1973.

Draft Page 85

Although information derived from aerial photography is primative, it

allows the determination of areas logged, approximate dates logging occurred

in a range of years, and intensiveness of logging, as well as subsequent

recovery rates. In addition to aerial photography, information is available

through the Department of Forestry which maintains a record of timber harvest

plans as mandated by the Z'berg-Njedley Forest Practice Act of 1973. These

plans detail the area to be logged, erosion hazard rating, percent and type of

harvest, reduction of coverage, harvest methods, road construction, and miti-

gation of potential adverse effects including stream protection and fish and

wildlife protection. Accordingly, knowledge of timber harvesting patterns and

practices is most inadequate before the 1920's, but progressively improves to

the present.

Figure 7A, displays the history of timber harvesting in Pescadero creek basin

on a decade by decade basis since the 1920's. 3 Logging activity dates prior to

1940 are mere approximations deduced from apparent revegetation shown in 1941

aerial photo, while activities between 1941 and 1971 are derived from aerial

photos and activities subsequent to 1972 have been directly transferred from

CDF records.

The acceleration of natural processes resulting from these activities is

difficult to quantify, as well as the amount of sediment introduced into the

system and the rate at which it moves downstream and enters the marsh. How-

3 Bibliography for Timber-Harvest Map

Aerial Photographs 1941, 1956, 1963, 1975, 1982 California Department of Forestry Timber-Harvest Map 1973-1984. western Ecological services company, 1983, Natural Resources Management Pro­gram for Pescadero Creek County Park.

Draft Page 86

ever, it is fairly reasonable to assume in a qualitative manner that logging

activities performed over a span of one hundred plus years, throughout a

majority of the watershed have accelerated the natural processes of erosion

and sedimentation.

Land-use patterns in the watershed have remained relatively stable over

the past century. What has changed dramatically in the past decades are

land-use practices as a result of changes in technology. Agriculture and

timber harvesting have become increasing mechanized, and chemicals have become

a more and more significant component of such businesses. Accordingly, such

activities have waged increasing impacts upon their surrounding environs in

terms of erosion and contamination.

6. Recommendations

This section includes a prioritized series of recommendations for direct

management action, as well as discussion of institutional roles, maintenance

plans, erosion-control, and continued monitoring and program assessment. For

the purposes of clarity, the recommendations are differentiated into those

affecting the lands under the direct control of the State through the Depart-

ment of Parks and Recreation, and to those in the remainder of the watershed

under private and other public agency controls. l Little) Butano state Park

lands are included in this latter category for geographic continuity. The

priorities suggested herein are advisory only, and are based primarily upon

the foregoing analyses of the physical and biological systems. They therefore

do not accommodate the very real institutional realities of budget, manpower,

and public impact. These priorities will need to be modified by the State and

other interested groups to effect the wisest rehabilitation and reclamation

Draft Page 87

goals within the context of realistic feasibility.

As stated in Sections 1 and 2 of this report, the goals of the recommen-

dations provided here are to both rehabilitate and restore the function and

longevity of the beach-lagoon-marsh system to that of a slowly-changing pro-

gressively infilling naturally-functioning tidal-estuary;coastal-marsh system.

These recommendations are tempered strongly with the realistic understanding

that coastal salt marshes must progressively decrease in area through geologic

time under today•s sea-level and climatic conditions, and that public funds

can wisely be spent best to develop and enhance natural saltmarsh system func-

tions, and not to force it to be frozen at some point in its natural evolu-

tionary progression. To this end, these recommendations are modest in scope,

generally self-perpetuating, low maintenance, and "restorative" in nature.

Although sound hydrologic engineering analysis is used to back these recommen-

dations, they do not intend to directly "re-build" or "re-design" the coastal

system to achieve direct and immediate full function as hypothesized for the

1854 base-line state. that early condition is one that can never be reached

and should not be sought. It is used as a model to provide a clear idea about

natural hydrologic function and balance. It is this natural function which is

the clear and direct goal of these recommendations.

~·1· Lower Marsh/Lagoon/Beach ~

The strategy behind these recommendations is to restore beach dynamic

function, enhance and restore tidal exchange, increase stream sediment and

tidal sediment flushing, and decrease potential complications between state

Park management goals and utilization of neighboring properties. As a direct

result of these actions, biologic function of the marsh and tidal estuary will

Draft Page 88

be enhanced and options for development of wildlife habitat are increased.

Three classes of priorities are developed. Highest Priority (Priority 1)

actions are those needed immediately to restore lost function. Priority 2

actions are needed to maintain or enhance natural functions, such as flushing

of sediments by tidal and flood action, and to protect against use conflicts

and potential liability. Priority 3 activities will insure continued function

of restored lands or will lengthen the periods of time that those functions

will continue without cessation.

~·!·!· Priority one Recommendations

1). DIKES. Dikes should be managed so that sediments borne by the streams

are dropped on the delta-fans leading into the marshland area and not, as

at present, carried into the tidal estuary except at times of highest

runoff floods. Dikes should also be breached and modified to maximize

tidal exchange volume and runoff flood storage. Further, these modifica-

tions may be made in such a way as to maximize protected nesting habitats

above tidal flood influence and the reach of non-swimming terrestrial

predators. Finally, some existing dike segments may be maintained and

enhanced to maximize storage of water in areas now only marginally wet-

lands and to maximize freshwater habitats.

Diking has been a part of the Pescadero marshland environment for as

long as known historical information permits review. The 1854 map (Fig.

1) shows a road along a right-bank elevated-area along Pescadero creek

from the townsite (shown on the 1895 update) continuously to Pescadero

Beach. Both sides of Pescadero creek are shown as not characterized by

wetland vegetation. In part this is doubtless the result of natural

Draft Page 89

levees, deposited by that larger creek during high overbank flooding,

which would have been more common with a naturally-functioning readily­

flooded marsh lowland area. Butane creek also shows a small area of

natural levees. Since potatoes were being grown in the marsh area at the

time of the 1854 survey (San Mateo co. Historical Soc., pers. comm. ), it

is reasonable to assume that at least the road alignment area may have

been along a levee/dike area, built and maintained by early settlers.

rt is recommended that existing dikes be modified to permit inflood­

ing by tides, especially by early-winter overbreach tidal floodwaters.

To this end it is necessary that dikes be breached with passages of suf­

ficient width and depth to allow the rapid inflow and outflow of tidal

waters. Since the site of the present Highway one bridge will ultimately

comprise the limiting channel for tidal exchange, artificial breach

dimensions should be approximately equivalent to the size of the lagoon

outlet. This will, in theory, permit any single area flooded by tidal

action to drain on ebb tide or beach break-out at a rate which is not

limited by the size of the breach. Breaches should then be constructed

to be approximately 280 feet wide and 2-4 feet below the levels of the

areas being drained. Dikes were recently breached by state Parks in

several places but insufficiently to allow free tidal exchange. Without

a deepened outlet channel, no breaching effort alone may be effective in

increasing tidal exchange volumes to critical magnitudes.

Referring to the Figure 5 illustrating dikes, the following breaches

are recommended: 1). The site of the present breach at the west end of

the North Butane dike against the coastal terrace should be expanded to

the requisite 280' width. Depth at present is adequate. 2). The

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triple-junction point where the dike separating Middle and North Butane

marshes meets the Butane creek left-bank dike should be removed com-

pletely. This is the most critical single dike modification. The breach '----......-~--·-~~"'W'-"

should be of at least 280' width and be to at least the depth of the

present thalweg of Butane creek. 3). The Middle Butane-North Butane dike

itself lies directly in the channel of what was once an important tidal

distributary. Five hundred feet of this dike should be removed to sea

level datum +2.0' at the south end of this dike. The breach at the

Butane Creek end of this dike should be designed to allow flood overflow

from Butane to enter both Middle and North Butane marshes, while the

500-foot breach will allow the Middle Butane waters to reestablish

drainage into the North Butane distributary. 4). The present breaches at

the south and north ends of the dike between East Butane and Middle

Butane are ineffective but innocuous. The breach at the south end should

be extended to 280' width at the present depth, to drain overflow of

flood waters from Butane creek. 5). The pr,esent breach at the east end

of ~a~t Butam? marsh should be deepened approximately 3 feet to permit

overflooding at even modest annual discharge peaks of Butane creek.

Since the east end of the marsh will deliberately trap sediment corning

from Butane Creek and will thus relieve some of the flooding pressure on

Pescadero creek at the Butane Creek bridge, this overflow site will

require maintenance to keep it free and functioning.

Breaching the North Marsh dike effectively is difficult. 6). The

site of the present bridged western breach is probably best, but of

inadequate width. This should be made wider to at least 280 feet.

Breaching this dike farther east is unlikely to be effective since Pes-

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cadero Creek can infill such breaches through flood overbank sedimenta-

tion. North Marsh is flooded tidally, particularly with beach-bar flood-

ing, but should also be able to accept direct overwash through North

Pond. If that North Pond circulation can be reestablished, even infre-

quently (once a decade), then North Marsh may periodically become a major

ponded area if desired for wildlife purposes. In that case, breaching to

increase regular tidal exchange as proposed here might be reconsidered,

and the present breaches refilled. 7). The "outlet" channel at the south

end of North Pond should be reestablished. If overwash from the beach

can be reestablished, then an initial dug opening of approximately .20-

foot width to a depth of mean sea level +2 feet will permit the estab-

lishment of a natural (wider) channel with the next overwash. However,

if the beach overwash flushing cannot be immediately established, then it

may be prudent to install a weir with removable flash-boards, locked to

prevent public interference, with at minimum a 16 square-foot capacity

below a water-surface elevation of mean sea level +4.0 ft. In effect,

since the water surface of North Pond may rise to +5 to +6 ft msl on an

average year, this control channel will have to extend from the top of

the dike at about +7 ft, down to a channel bottom concrete weir located

at an elevation of mean sea level, for a 4-foot width channel. This

would be operated to spill water rapidly into North Pond when North Marsh

was flooded to +6 feet with salt water, and to maintain water in North

Pond to that maximum elevation for as long as possible, with the option

to drain the pond nearly completely during low winter tide stages.

Questions arise about public use of dike remnants. The trail along

the north side of Pescadero Creek could easily be maintained if it con-

Draft Page 92

tinued to be connected to the Highway One trail head by a bridge over th~

280-foot breach. The cost of such a temporary bridge needs to be con-

sidered, as well as its periodic replacement after major floods. Access

to the left-bank Butano creek dike is more of a problem. Since all

access dikes plus the middle will be breached, it may be well to consider

not making provision for public access, and to even specifically break up

the west Middle Butano dike to provide nesting habitat. There is no

hydrologic justification for added breaching, but there may be other

valid reasons for it, and it is not detrimental to the restoration of

hydrologic function.

The dikes of East Delta Marsh comprise a unique case. Priority Two

recommendations specify a breaching of the left bank Pescadero creek dike

at the extreme east limit of state property to allow infrequent (10-year

return period) flood overflows of Pescadero Creek to join the Butane

creek system through East Delta marsh. Thus, it is necessary to provide

an outlet for these waters. No breaching of the East Delta marsh dike

system is here recommended because consideration may wish to be given to

the operation of the present East Delta Marsh drainage structure for

habitat enhancement. That marsh area is today drained through a control

structure last constructed by Mr. Tommy Phipps in the last decade. The

Phipps tide gate is located just south of Round Hill at the northwest

corner of the East Delta marsh. The top of the gate is a 7.18 feet msl.

It serves today to allow drainage of precipitation and overflows out of

East Delta marsh, but restricts tidal and beach overtopping floods from

entering East Delta marsh until they rise above 7.18 feet. The tide gate

is built into a concrete faced dike section of sufficient width to ade-

Draft Page 93

quately allow for outflow from the proposed eastern Pescadero creek over­

topping channel. Thus, there is little fundamental hydrologic reason to

alter the diking of East Delta marsh except as it may relate to alterna­

tive solutions to the problem of flooding of agricultural lands of neigh­

bors to the state Park property (see Priority Two recommendations).

With minor modifications, the Phipps Tide Gate could be made to

operate as a removable darn, functioning normally in the opposite send of

that of today. The structure is well-constructed and would be service­

able for at least another decade with minimal maintenance. It could be

made to hold back wintertime precipitation impondments of fresh water,

and to release same out into Delta Marsh, thus providing a summer-time

fresh-water;salt-water interface at the east edge of that marsh. This

interface in this site today is seen to be habitat for very many small

fish. When tidal waters rose above the base of the tide gate, at about

5.0 feet, salt water would move into the East Delta marsh. Alterna­

tively, the weir at the tide gate could be operated as a fixed darn with

flash boards to maintain the easternmost portion of the marsh as dom­

inantly fresh-water marsh habitat.

It is observed that a wide range of microsites with differing salin­

ities are found today in the vicinity of the Phipps tide gate. Soils are

generally quite saline since the area is normally subject to periodic

flooding by tidal waters. salt tolerant species of plants predominate.

In winter, when fresh water flows out of the Phipps tide gate into the

main Delta Marsh pickle-weed flats, the brackish water organisms cluster

around the bases of these highly saline plants that are then releasing

salts accumulated in summer. Freshwater organisms find habitat among the

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freshwater aquatic plants that line the drainage ditches leading from

East Delta Marsh.

salinity tolerances.

There is thus an overlap of species with different

2). BEACH AREA: A primary recommendation for the beach area is that the North

Pond overflow channel be reestablished. This channel connects the back­

beach area with North Pond only at times of coincident high tide and high

wave swash (short period, high amplitude winter waves). such overflow is

not expected annually, but will occur several times within a 10-year

period. The lagoon;estuary system may or may not be open to the sea when

overwash occurs. The most probable time for such overwash is during the

months of November and December. At the t~mes of overwash, the fore­

beaches are generally inaccessible to the public. The overwash channel

that should be reestablished lies immediately south of the State Parks

Pescadero Beach parking area. The channel alignment in no way interferes

with or is obstructed by the parking lot or kiosk. On the beach proper,

reestablishment of the natural channel is simply accomplished through

selective log removal. Logs are placed as they are, presumably, only to

prevent access to the beach by motor vehicles. A chain locked to posts

can cover the whole region of access.

The more difficult problem is the barrier to the North Pond created

by the Highway one berm. we recommend a rectangular box culvert, so•

wide, with its base at mean sea level, and oriented approximately N 45°

w. such a culvert should be accessible from the beach side for clean­

out. Alternatives include a causeway, a small highway bridge, and a

series of pipe culverts. The first two are reasonably costly, but effec-

Draft Page 95

tive. The pipe culverts would be inexpensive but would not be easily

cleaned by the force of tidal water or human maintenance. At the time of

construction of the Highway one berm, according to the state Highway

archives, most of the proposed highway route across the dunes was indi-

cated to be about 30+ feet above mean sea level. The north overwash

inlet was shown along the centerline of the alignment at xl-2 feet above

sea level, and had to be filled to its present level by hauling material

from the north. If cooperation from Cal-Trans cannot be secured for res­

toration of this natural tidal channel, state Parks may wish to consider

simply managing its beach environment to restore natural function, and

allowing the highway to overtop upon rare occasions when the beach-berm

is overtopped at an elevation of about 10 feet above msl. These occa­

sions are too rare, however, to provide functional restoration of the

North Pond environment.

Another priority one management goal should be the restoration of

the potential for tidal exchange and sediment flushing at the mouth of

Pescadero Creek. Under the present highway, tectonic, and sediment flux

environment at the mouth of Pescadero Creek, it is our recommendation

that the most cost-effective, least disruptive, and most certain restora­

tion of function can be best achieved by deepening the bedrock channel

upon which Pescadero creek flows to the sea at the south end of the

beach. After careful consideration, this most "unnatural" action is

believed to best retore natural function. Once completed, it will be

completely invisible under the beach or floodwaters. Alternatives con­

sidered include dredging sediment from the tidal estuary, complete relo­

cation of the Highway One bridge and use of a causeway long the full

Draft Page 96

length of the Pescadero Beach region, use of marsh lands as pump-storag~

reservoirs for sudden releases to be combined with high runoff events to

effect sediment flushing, and other heroic measures.

The present water course, held at the south end of the beach pri­

marily by longshore beach drift, cannot be expected to seek any other

route to the sea so long as the Highway one berm remains in place and

high sediment yields continue from the watershed to support a wide beach.

With continued tectonic uplift of approximately 1' per century on the

Pigeon-Point block at the mouth of the creek, and continued "lengthening"

of the course of the outlet by the northward movement of the left side of

the creek at its junction with the sea by on the order of 10' per cen­

tury, even the short period of the last so-years of artificial conditions

could coincide with a "defeat" of the ability of the tidal outlet to

function in the fashion of a normal estuary.

It is recommended that a channel be constructed, in the fragmented

partly-decomposed volcanic bedrock, to a depth of 10 feet below sea

level, for a width of approximately 100 feet. This will involve the

removal of approximately 6000 cubic feet of rock and sediment, in the

surf zone, with a deeping of the channel by as much as 9 feet compared to

its present position. This is a significant task, primarily because of

the necessity to work in the wave zone at times of lowest (-5'} tides in

June when waves coincident with lowest tides are minimal. The bedrock

bench has been surveyed to a minimum elevation of -2.45' approximately

100' offshore, beyond the end of the point (AR144, elev. 39.54' ). This

bench can be traced on aerial photos to a point approximately 1000 feet

north of the outlet of the creek. It is therefore not feasible to force

Draft Page 97

the outlet northward around the subsea bedrock barrier. The channel

would have to be deepened from the approximate position of "the bend"

about 350' downstream below the west side of the highway bridge, to a

point estimated to be approximately 250' further in a northwesterly

direction. Present stream bed elevations decline from +0.76 feet at "the

bend" to approximately -2.0' in the surf zone offshore. the surface of

the tidal portion of the stream bed is primarily a series of boulders,

some apparently movable, but most being upward projections of bedrock

pillow-basalts. Since these are highly weathered where exposed in the

sea cliffs, it is reasonable to predict that they may be readily moved

with a large back-hoe. Such an excavation vehicle would have to be

attached by cable to a larger caterpillar tractor stationed on the beach

so that the latter could belay the former, and pull it to safety if

needed.

Plate 5 shows the bed of the outlet channel at "the bend" where

water surface elevations are controlled by bedrock. The deepened channel

should be located to most effectively allow the highest winter flow

volumes moving N 60° W under the Highway One bridge to exit directly to

the sea around the rocky point (not through the tunnel--see priority

two). This places the deeper modified channel bed north of the channel

as shown in Plate 5. The 100-foot recommended width is not alone suffi­

cient to carry the full outlet volume of the watershed at flood flows,

but will provide a critically needed deep central channel for sediment

transport from the deepest point in the lagoon about 500-750' upstream

from the bridge. The -10 foot msl depth necessary is based upon the

reported observed scour at the bridge site following the storm of Feb.

Draft Page 98

28, 1940 (Bridge construction Report, p. 18) which showed, in June, 1940,

an increase in depth of 7-8' at the bridge alignment compared with the

August, 1939, surveys. The beach width of 4-11-41 of 260' was the nar­

rowest of record after highway construction so we can assume that the

major storms of 1939-40 allowed beach retreat to permit northward exiting

of the channel in a position no longer possible today due to the beach

width and highway berm.

3). BEACH BAR. The beach bar should not be artificially opened. It should

be allowed to impend runoff and wave overwash to heights determined only

by beach conditions and runoff volume. It should be allowed to "break­

out" naturally, at times of coincident high lagoon stage and, upon occa­

sion, high runoff. Such breakouts are much more effective in tidal sedi­

ment flushing action seaward, and can help to evenly distribute incoming

sediments throughout the lagoon-marsh area. High lagoon levels enclosed

by beach-bar conditions insure opportunities for salt-water flooding reg­

ularly to elevations of +6 to +9 feet above sea level, and thus help to

maintain saline soils and salt-tolerant vegetation in the lower marsh

areas. current dike heights of +7 to +14 feet insure that nesting sites

at various elevations above tidal flooding can be secured for avifauna.

The single exception to the recommendation against artificial open­

ing would be to allow such opening upon rare occasions when flood waters

impended by the beach-berm threaten serious damage to private and public

lands and structures built above +9 feet ms1. The most likely property

to be affected is the private land at Water Lane adjacent to park pro-

perty. Here recommended land exchange or protective works should be

Draft Page 99

designed to allow flooding to 9-feet upon the relatively rare occas~ons

when beach bar conditions allow it. Flooding to these elevations from

stream runoff floods would be expected to occur about as often as from

beach-bar controlled conditions. Allowing opening artificially at +9' is

sufficiently infrequent to have any measurable effect upon state Park

lands.

2·1·£· Priority ~ Recommendations

1). PESCADERO CREEK OVERFLOW. The artificially maintained acute-angle bend

in Pescadero Creek at its point of contact with the easternmost limit of

state Parks land presents a continuing maintenance and possible liability

problem. This site has repeatedly flooded at high stages, and overtops

the inadequate dikes built along the left bank of Pescadero creek. The

waters that flood out of the channel at the site of this greater-than­

right-angle bend generally flood agricultural fields under private owner­

ship and comingle with regularly recurring floodwaters from Butano creek

to pond against the East Delta Marsh dikes. The course of Pescadero

Creek at this site is shown on the 1854 map in approximately the same

position as it exists today. The alignment is definitely anomalous with

a straightened reach extending from the townsite of Pescadero to the

state land boundary, followed by an acute dog-leg bend from whence it

exits along a mostly controlled route to the sea through the narrow low­

land course north of Round Hill. Some of this river course may be a

direct result of faulting, but much is believed to be attributable to

human change. The watercourse today is "re-"located so as to maximize

usable agricultural bottomlands.

Draft Page 100

It is recommended that a new overflow area be established to carry

floodwaters above 3000-5000 cubic feet per second that could otherwise

erode and overtop dikes in unpredicted places. the new "channel" should

extend from the site of the redwood log cribbing at the right-angle bend

in a southwestward direction along the approximate eastern border of the

state's property. It should be designed to carry water only when the

stage of Pescadero creek rises above what would be the normal overbank

level at this site assuming that the present protective works were not in

place. The width of the breach in the protective works should be 150 ft

with the dike margins cut back to a 1:4 slope. This opening will carry

the expected 100-year discharge overflow. Depending on the chosen option

for dealing with the tidal flooding of the adjacent agricultural lands, a

new dike will have to be established along the eastern margin of the

state property connecting with the upstream breach site and extending

along the property line at least to Water Lane. This dike is provided to

protect the adjacent agricultural lands from flooding when serious over­

topping occurs on a recurrence interval of between approximately once in

five years and once in 20 years.

The west side of the overflow "channel" need not be protected.

Flood waters will follow the lowest route as they have in the past before

the construction of protective works to flow west-southwest to the base

of the hill in the vicinity of the present temporary park headquarters

buildings, and thence into the tidal portions of East Delta Marsh. The

natural course of these flood overflow waters will be to flow against the

base of the hill, along the road connecting the present headquarter

buildings with Round Hill and the Phipps tide gate. The waters will flow

Draft Page 101

adjacent to that road southwestward to the southernmost point of thaL

road, from whence they will flood out into the marsh area and flow

approx~mately due westward. This is reconstructed from the topography

and from gravel deposits left by past floods. Under the present manage­

ment scheme as recommended herein, these waters will pond against the

westernmost East Delta Marsh dike and overtop the concrete weir at the

Phipps tide gate. In the past, before modification, these waters would

have joined Butano Creek at the point of its northernmost swing, which

helps to explain why Butano•s channel takes such a bizarre course to the

sea. In fact, Butano today flows in an old channel of Pescadero creek

from East Delta Marsh westward. The ancestral Butano channel is doubt­

less that now filled by the northern part of the Middle Butano/North

Butano dike, which will be removed under this management plan.

The present Pescadero channel, from the site of the easternmost

flood breach, will continue to carry ordinary annual discharges and its

valuable and well-developed wildlife habitat will be preserved. The

present redwood log cribbing at the site of the bed can be partly left in

place to provide a sill over which flood waters must pass to enter the

overflow "channel." During high flood states, approximately once in five

years, this overflow condition will render the Delta marshes, Round Hill,

and the hill at the present headquarters buildings, an island. It will

be inaccessible to vehicles for a number of days with each major flood.

If access was necessary, perhaps a cable-way footbridge could be con­

structed across the present main Pescadero Channel, either at Round Hill,

or north of the old fish-rearing ponds where suitable trees and stable

high banks exist. It is specifically not recommended that the present

Draft Page 102

water Lane access or the breached left-bank overflow channel at the dike

be considered for bridging for all-weather access. For large flood

events, these sites would have high-velocity waters of up to 10 feet per

second and would be difficult to bridge safely in a cost-effective

fashion.

2). LOWLAND NEIGHBORING PROPERTY. The Water Lane properties, presently owned

by Mr. Ed Camponetti, present a specific management problem. It is

necessary to allow the marshlands to be flooded to their natural depths

at times of beach overwash with beach-bar closure. In so doing, the

flooding occurs in all areas of the potential (1852) marsh lands on state

property, but also occurs on the neighboring water Lane property. The

extent of lands naturally subject to flooding on a regular periodic basis

every several years can best be seen by reference to the 1854 map, look­

ing specifically at the wetland vegetation. The san Mateo County topo­

graphic map series (San Mateo co. Planning Dept., various dates) also

accurately show the lowland areas subject to regular flooding as those

below what they depict as about +5 feet elevation. The 1854 map, and the

regions of wetland soils as seen through the plowed fields on the 1928

aerial photos are the best guides to flooding on a regular basis since

the soils and vegetation best reflect the naturally functioning system.

The present dikes along Pescadero Creek outside of state Lands are

of inadequate height to protect against the 100-year flood. They are

overtopped on an approximate 20-year flood stage. If one were simply to

erect a dike and pump system to protect the private Water Lane properties

from tidal flooding, then there would be ponds formed behind those dikes

Draft Page 103

at times of river flooding. No pumps could keep up with the discharge of

Pescadero Creek in flood (the 100-year event, discharging an estimated

16,700 cfs in Pescadero Creek, would put perhaps 6,400 cfs over the

dikes). Such a dike might be effective if it were constructed with a

large tide-gate to allow through-passage of waters from the east.

The following three options are recommended, in order of increasing

management complexity and difficulty. l). Effect a land

exchange/purchase to secure tidal flood rights to a management unit of

approximately 11.7 acres (10.5 acres flooded plus lands marginal to them

with diminished agricultural access). The state owns 6.9 acres of good

artichoke lands immediately north and east of the old ranch buildings

housing the temporary headquarters. However, that land will be subject

to reduced access during floods of approximately a 5-year recurrence

interval, and to coarse gravel sedimentation over approximately 2 of

those 6.9 acres. 2). construct a diking system approximately 3000 feet

long such that a low (4-6 ft) dike encloses the boundaries of the private

property with East Delta marsh, while a higher dike reconstruction of 6-8

feet extends along the right bank of Butano Creek from Pescadero Road to

the Park boundary. The dike would then comprise approximately 1000 feet

of low berm and approximately 2000 feet of high berm. Then, using

materials dredged by pump-dredge from Butane Creek channel locally,

infill the private land to raise it all above the level of regular tidal

flooding (approximately +7 feet above msl would be necessary). the

volume of fill required would be approximately 44,500 cubic yards. This

is about 41 percent of the average annual sediment discharge of Butano

Creek and about 3-times the volume of loose sediment stored in the adja-

Draft Page 104

cent Butane Channel. The top and face of the dike enclosing the infilled

lands would have to be faced with non-eroding materials to withstand

overwash from high floods and erosion by overflow currents along its

base. 3). A high dike would be constructed beginning at Pescadero Creek

and extending completely around the private lands, approximately 4100

feet long, ending at Pescadero Road bridge over Butane creek. This dike

would have to have high capacity marginal drainage channels along its

full length on the "private" side. These would be fed to a sump area at

the lowest point and non-flood seepage would be pumped to Butane creek.

At flood stages, when waters from Butane creek (2-4 times every year), or

Pescadero creek (once every 20 years) enter these lands or when rainfall

intensities are high and runoff exceeds pump capacity, a swing gate near

the sump would be opened to allow passage of these waters through a 75-

foot concrete weir into East Delta Marsh.

The first option has the advantage of far greater simplicity, no

liability or maintenance problems and, in the long run, lesser cost. The

other options can only be effected with a loss of potential wetlands and

with a continuing problem of casting blame for various kinds of flooding

that will continue to occur. The latter two options have the advantage

of allowing for the possible construction of high dikes (to 11 feet above

mean sea level) and thus not necessitating any artificial intervention to

breach beach-bars when lagoon waters rise above the state property boun­

dary, as they will on rare occasions (perhaps once in so years) but the

costjbenefit ratio for such high dikes is doubtless negative.

Draft Page 105

Both of the foregoing recommendation categories raise the mutual

issue of the design requirements for the dike to be constructed from the

Pescadero Creek overflow breach along the west side of the private pro-

perties. Using Corps of Engineers design criteria (C of E, 1969, p. A-

39) and FEMA predicted flood levels (FEMA, 1982, section B), both of

which were verified in the current management plan study, standard good

engineering practice would demand that the top of the newly constructed

dike be built to +18 feet above msl to allow 2 feet of safety/freeboard

for the predicted 100-year +16-foot flood surface. This elevation would

have to be maintained over the full linear extent of the dike because it

is determined primarily by the backwater calculations from the outlet

channel near Highway One. But the dikes upstream from state property,

into which the new dike would be integrated, are approximately 4 feet

lower. And Butane Creek is completely unprotected by dikes in its usual

sites of overflow. It is thus recommended that new dikes be constructed

to the same protective standards as those of the existing Pescadero creek

dikes, subject to legal review by state's attorneys. This strategy will

permit the State to protect adjacent lands from flooding by waters passed

to it from channels upstream. In the event of high magnitude floods

overtopping all dikes, the state will not be responsible for damages from

upstream conditions outside its control. If land exchanges can be

effected to place the Water Lane properties subject to regular tidal

flooding under state control, then marginal dike design should be such as

to protect adjacent private properties from Pescadero Creek discharges up

to the height of the present dike only. The dike should be extended

about 100 feet southwest of the southwestern limit of private property

only, since that will accommodate and protect against flood damages by

Draft Page 106

Pescadero Creek waters alone. Flooding of private lands would then still

occur, but as the result of Butane Creek overflow or lagoon mouth backwa­

ter elevations not under any form of control by state Parks.

3). BEACH TUNNEL. The tunnel at the mouth of Pescadero Creek, with a floor

elevation of -0.3 ft msl, does not permit effective drainage of the tidal

estuary portion of the lagoon. It does, however, effectively prevent the

lagoon from reaching elevations sufficient to effect tidal flushing upon

breakout and prevents flooding of tidal wetlands when beach conditions

are such that the lagoon is closed by a beach-bar abutting the rocky

point but not plugging the tunnel. This is undesirable for natural

management and restoration. The tunnel should be effectively plugged

with concrete and rock cofferdams at each end.

4). BUTANO CHANNEL AT PESCADERO CREEK BRIDGE: The recent aggradation of this

channel of 5-6 feet in 30 years greatly increases the frequency of over­

bank flooding. The average annual volume of sediment moved under the

bridge is unknown, but the average volume moved in the whole Butane chan-

nel may be on the order of 70 ac-ft per annum. The volume of fresh

unconsolidated fine sand stored in the channel on State lands is about

15,000 cubic yards in an unconsolidated state. In the "2nd" option for

protection of lowland neighboring property, described above, a fill of

44,500 cubic yards would be needed, or two and one-half years of pump-

dredging of the Butane creek channel. Such dredging could not be

expected to provide any kind of long-term relief from channel flooding

since at least an order of magnitude more unconsolidated sediment is

stored in-channel immediately upstream of the bridge.

Draft Page 107

~·~·l· Priority Three Recommendations

1). PUMPS, POLES, AND BRIDGES. Numerous "artifacts" of agricultural use

remain throughout the marsh lowlands under direct state control. The

dikes and tide-gate have already been addressed in higher priority recom-

mendations. There are no overriding reasons to maintain or preserve the

remaining lowland "restoration artifacts" from the standpoint of form or

function of the marsh-lagoon system. Pumps, hunting blinds, pump-houses,

bridge members, and fence remnants can probably all be removed. The sin-

gle group of artifacts that may have a function in the restored system is

that of the power and fence poles. A preliminary biological inventory of

the lowland terrestrial areas that will be flooded under the recommended

management plan shows a very large population of meadow voles and other

microtenes (reference). A significant population of raptors exist to

prey upon this population, and upon other prey birds (reference). It is

possible that, for wildlife management reasons, existing poles, including

even small fence and miscellaneous posts, may wish to be left in place to

aid the raptors. The increased frequency of flooding of lowland areas

will probably not be so frequently that it will eliminate microtene habi-

tat.

2). VEGETATION CONTROL. The subject area of control of exotic vegetation

within the State Park's area is largely outside the purview of this

management study. The upland areas of dikes within the marsh proper, and

the bedrock hills and terrace surfaces of the park lands, are character-

ized by significant exotic vegetation. Changes in the vegetation have l ~~ ... occuicc

1

and r·i:;:··most obvious in regard to eucalyptus and pampas-grass

(Violis 1979}. The introduced eucalyptus, probably introduced in the

Draft Page lOB

1880's (Kinney, 1895) has proven to be a valuable time-marker for pollen

analysis of coastal lagoon sediments nearby at Bolinas (Bergquist, 1978).

The trees at Pescadero provide nesting habitat for many birds and shelter

for what may be an unusually tall and robust local population of deer

(reference). Exotic vegetation within marsh areas subject to salt-water

flooding includes residual artichoke and straw-flower plants, as well as

other introduced species (Frenkel, 1978). Returning the marsh to a more

natural tidal and flood cycle will tend to restore much of the native

vegetation. This has happened in salt-marsh areas elsewhere in the

region (Atwater and Hedel, 1976).

A potential area of concern where present vegetation management does

affect system function is that of the coastal dunes. Elsewhere in coa­

stal California, introduced species have tended to stabilize~ coastal

dunes and result~ in higher dune elevations (Casper __ ). The 1854

map, when compared with the profiles of the dunes for Proposed Highway

one corridor in the late 1930's, appears to be the same in each case and

.,,a,"i\ll'iittlii!!''§ein:e as that found today, with the single major exception of the

overwash channel region into North Pond. What has changed significantly

is the areas of the "hook" of Pescadero Beach, east and southeast of the

north highway bridge abutment. The presence of the bridge approach berm

rising to +30 feet msl, and the presence of much introduced stabilizing

vegetation on both sides of the highway, may have greatly stabilized the

"hook" area.

Judging by the _;t:o~gra,J?hy and the old channels visible in aerial

photographs, it is probable that the hook area was periodically washed

out to sea by circulation of waters southward from North Pond during

Draft Page 109

overwash, and by major runoff floods such as that of 1955. We can see

from imbedded debris and logs at an elevation matching that recorded on

the bridge for the 1955 flood, the highest of record for runoff

discharge, that the floodwaters overtopped much of the area shown as

active dunes on the hook as shown in the 1854 map. Today, with source

sands greatly reduced through introduced vegetation, the dune migration

cycle is essentially aborted. With recommended restoration of North Pond

overwash and flushing, and with future high runoff floods, we can expect

the backdune sand areas to be flushed out and not replaced. It is thus

recommended that consideration be given to allowing vegetation to be

trammeled out in the backdune "hook" area to more nearly emulate pre­

stabilization conditions, and that this also be encouraged in the isthmus

between North Pond and North Marsh. This will allow ready erosion by

flowing waters to develop and maintain through-circulation. Some sand

will be replaced annually through minor erosional scars in the ice-plant

and introduced grasses of the foredune areas, so long as people continue

to walk there. This is probably desirable, from a natural systems

viewpoint, so long as it does not significantly interfere with highway

maintenance. sands removed by highway crews must be returned to the

beach-dune-drift cell (see following section 6.3 on Maintenance).

Other vegetation control concerns center around channel maintenance

and riparian vegetation. This subject will be dealt with in detail in

section 6.3. In general, riparian habitat and vegetation should be

preserved. However, to maintain both a visitor interpretative program

and remain good neighbors with adjacent landowners, some channel vegeta­

tion maintenance is required, particularly the removal of log jams and

Draft Page 110

fallen trees that could cause log jams. This applies only to the upper

areas of the marsh with channel bed elevations of about +6 ft msl.

&·£· watershed Areas Above Marsh

The strategy behind these recommendations is to reduce sediment produc­

tion from upland source areas and, to the extent possible, slow the passage of

sediment in transit or in temporary channel storage into the marsh/lagoon sys­

tem. Since the marsh area has been receiving great quantities of sediment in

excess of long-term historic background but not historic peak levels, it fol­

lows that to permit the system to regain a measure of its tidal estuary func­

tions, it is necessary to carry out rehabilitation management in an environ­

ment of reduced sediment loading. To this end several management goals, if

implemented, would aid in rehabilitation of lower wetland areas and would

insure that habitats, once restored, would be able to continue functioning for

relatively long periods of time measured in centuries. Obviously, management

prescriptions for upland areas outside of state ownership require practical

cooperative mutually beneficial implementation strategies.

these are discussed.

Where possible,

The three classes of priorities are similar to those for the areas under

direct state control. In this case, highest priority (Priority 1) actions are

are those recommended to facilitate restoration of function downstream.

Without these actions, work downstream may be ineffective. Prio~ity 2 actions

are needed to maintain conditions leading to restoration downstream. Priority

three actions will insure long-continued function of the marsh/lagoon/beach

systems, once restored.

Draft Page 111

~·~·~· Priority one Recommendations

1). REVEGETATION. Areas of the lower channels of both Butane and Pescadero I

creeks are today rapidly eroding to providg a major source of sediment. /'',

In the case of Butane, these sites are believed to have contributed about

80 percent of the total sediment flux of the last 30 years. In the

Butane Creek channels, a channel length of about 3.5 miles centered on

the site of the junction of Butane and Little Butane creeks is character-

ized by significant present active bank instability. Preliminary channel

surveys identified about 20 sites between the Butane Falls Tract and a

point about 1.25 mile below the junction with the Little Butane where

active bank undercutting at times of high flow had contributed many hun-

dreds to several thousands of cubic yards of sand-sized sediment in sin-

gle flood-flow events, such as those of 1982. In general the stream is

flowing on resistant "bedrock" or resistant clay plugs. To accommodate

high flows carrying sediment or log debris, these streams can only cut

laterally, which then contributes disproportionately larger amounts of

sediment downstream, and the process becomes self-amplifying. Only

well-vegetated channel walls can resist lateral undercutting, especially

those with imbedded Pleistocene riparian forest stumps or log jams in-

situ in the channel banks.

It is recommended that these sites of high sediment production be

inventoried and that a replanting effort be undertaken on a modest scale.

The sites are generally moist and could easily be replanted. The bene-

fits to local landowners who are losing agricultural lands to channel

erosion are obvious. The benefits to the marsh are equally great, and

the anadromous fishery of Butane Creek will benefit from the reduced sand

Draft Page 112

stone.

Equally important on Butane is the removal of any log jam that ini­

tiates the lateral cutting of unconsolidated channel banks. This is both

a one-time effort and a maintenance problem. There are massive log jams

at and above Butane Falls, below the Butane Falls tract, and smaller

accumulations in the channel along the critically eroding reaches of both

Butane and lower Little Butane channels. A cooperative "channel-watch"

program is recommended, using local residents to spot potential trouble

spots. An effective technique in Butane creek would involve simple use

of chain saws to reduce logs to lengths of 4-5 feet that could then float

free in flood flows. care should be taken not to bring backhoes or other

heavy equipment into use that would destroy channel bank cohesion and

vegetative cover.

The Pescadero creek problem areas differ somewhat from those on

Butane Creek. Because the lower reaches of Pescadero do not follow the

active San Gregorio-Hosgri fault system, there is less volume of reex­

humed channel fill along its course. Where it does flow through agricul­

tural lands upstream from the town, there are high cut banks, which were

damaged in the 1982 flood flows like those of the lower Butane channel.

The terrace remnants in the upper Pescadero watershed primarily are made

up of coarse sands and cobbles, and are less readily eroded and moved by

the stream. Pescadero has a major sediment source in its middle reaches

centered around Dearborn Park, and extending approximately 2 miles up-

and downstream from that area. Here active translational landslides

directly enter the stream channel and provide sediment of all sizes to

the stream at rates that are dependent primarily upon the rate of

Draft Page 113

movement of these slide masses. The hillsides in this sensitive area

have been the sites of recent logging operations in the 1970's and 1980's

(see Historical Timber Harvesting map, Fig. 7). It is recommended that

an inventory be made of sediment sources in this area and that great care

be exercised in executing timber harvests (through their permitting pro­

cess with the state) and grading permits (through normal county permit

review). Some vegetation of toeslopes of actively eroding slides may be

considered. The raw slopes that are not associated with moving transla­

tional slide masses are not sources of continuing sediment input in the

same fashion as stream cuts in such deep-seated slides.

2). OFF-ROAD VEHICLE USE: A small area immediately north of Round Hill, just

outside of state Parks lands, has recently been used for off-road motor­

cycle use. The entire hillside bedrock area west of Bradley creek,

comprising some 2 square miles of watershed area, is highly subject to

deep gully erosion. This problem has been studied for State Parks by

Swanson (1982), who found that the bedrock unit on this west side of the

san Gregorio-Hosgri fault system was subject to deep massive gully ero­

sion at times when high cumulative soil water conditions coincided with

times of high precipitation intensity. Land use practices were shown to

clearly affect the susceptibility of a site to a renewed erosion cycle.

Deep and damaging gully erosion both on state property above North Pond

and in the drainages north of Pescadero has already caused serious dam­

age. It is recommended that cooperative efforts or purchase options be

considered to reduce the present damage and to permit vegetation to

prevent future problems. Gully control is the subject of the next set of

recommendation.

Draft Page 114

~·l·l· Priority ~ Recommendations

1). GULLY CONTROL: Gully erosion originating through soil piping outside of

State Park lands extends onto state lands at North Pond, and contributes

substantial quantities of fine-grained sediment (silt and sand sizes) to

Pescadero creek at other sites between Bradley Creek and the coast. In

almost all cases studied, actions or conditions on lands outside of the

Preserve boundary are responsible for the gullying. Aerial photo

analysis through the period 1928 to present indicates that the gullies

form periodically, and tend to heal over with vegetation. The conditions

favoring gully formation are a high clay content subsoil, a moderately

porous surface soil (favored by the presence of wind-blown sands incor­

porated into the surface soils after the formation of deep subsoils), and

high soil moisture levels accompanied by high intensity rainfall. The

meteorologic conditions of 1982 provided such conditions, as apparently

have other historical periods.

Four sites of gully formation directly affect the Pescadero marsh

system. A site just north of the northwesternrnost limit of the Preserve

boundary has been subject to repeated periodic gully formation. This

site is characterized by a major trunk gully that debouches directly onto

state Highway One. Sediments pass across the highway and onto the beach

at the north end of Pescadero Beach. Highway closures and damage to

beach facilities result from active gullying periods. A second set of

gullies arise along the approximate route of the pre-Highway One coastal

roadbed at about 300-feet elevation near the summit of the hill north of

North Marsh. Deep gullies (50-feet plus) have formed below this site of

impaired subsurface drainage, and they carry all of their sediments into

Draft Page 115

North Pond. The delta area forming in North Pond can be seen to have

formed entirely after the earliest 1928 aerial photos. The third area of

gully activity affecting the marsh habitat is that in the before-

mentioned motorcycle use area north of Round Hill. The final area is a

gently sloping land surface located immediately northeast of the

northeasternmost boundary of the Preserve, on agricultural lands now

apparently being left fallow. This site contributes sediment to the

fields and small ephemeral drainage that in turn feed it to Pescadero

Creek near the site of its "big bend."

It is recommended that measures be taken to reduce active gully ere-

sion in these four sites. Benefits to local landowners and for state

highway maintenance are obvious. Erosion control measures that would be

most feasible and effective here are not as obvious. Much work has been

done on this problem. The work by Swanson (op.cit.) at Pomponio Creek

immediately north of Pescadero has not yet generated solutions to the

problems except to restrict triggering by incompatible land uses. Work

by the National Park service at Golden Gate National Recreation Area has

shown that effective control can be achieved with a series of well-

maintained wooden check-dams. However, the conditions are different at

the Gold Gate headlands, and the scale of the problems is much smaller

than at Pescadero Marsh. Attempted dam construction in the lower reaches

of a major gully at Pomponio failed (.;

repeated,v owing primarily to the

large volume of water and sediment discharge. Clearly, for areas with

incipient or headward-cutting gullies, maintenance of a good cover of

diverse vegetation, rooting at multiple depths, is important. Even this

is difficult because the high soil water levels discourage deeper rooting

Draft Page 116

plants in the presence of a clay subsoil. once the gullies form, the~r

steep (even vertical or overhanging) cut slopes make revegetation very

difficult. Native brush species such as coyote brush seem particularly

ineffective. What is needed is a very aggressive plant that tolerates

sediment accumulation and is anchored by a dense rhizome-like root. such

a plant, if planted in the thalweg of the gully, would prevent its head-\

ward cutting and deepening. Pampas grass or other undesirable exotic \

species might prove to be the only effective ~~~~~at:,~,:,,,,:l'::~abilitation \

tools. Other methods that could be tried are a filter-fabric covered

with fine gravel and in turned covered by coarser anchoring rip-rap

placed directly in the bed of the channels upstream from permeable

debris-dams of brush, small branches, and jute netting placed on an arma-

ture of driven steel fence posts. such mechanical means have been used

effectively when well maintained in less-steep gullies in the arid

southwest. Their construction is covered in a series of u.s. Forest Ser-

vice Research Papers by Burchard Heede. It is recommended that serious

experimental efforts be instigated at the North Pond gully sites, as soon

as man-power and funds can be secured, to attempt to slow or halt the

growth of these major gullies. seeding or maintenance of a dense cover

crop on unused agricultural lands should be tried at the lower gradient

sites northeast of the Preserve. This could be effected on a cooperative

basis with the county Soil Conservation service agent and the landowners.

2). ALDER THICKET: Butano creek, from its junction with state Parks lands at

Pescadero Road upstream for a distance of approximately 1.2 miles, flows

in a lowland swamp of dense riparian vegetation. This area, which we

have referred to as the "alder thicket" comprises some so acres of twist-

Draft Page 117

ing anastomosing waterways through primarily a willow and alder forest.

The area is remarkable for its wildlife and for the virtual absence of

evidence of humans. It is of true wilderness character, where the moving

water and continuous sounds of birds in the mature overstory effectively

mask any sounds that might pass from the highways or townsite nearby.

The contiguous nature of the riparian corridor from the generally circu­

lar alder thicket area into the state Preserve provides a travel route

for birds and mammals frequenting the marsh. Birds nesting in the

thicket feed on plentiful food sources including the anadromous fish that

migrate through the maze of constantly changing waterways. Local lore

and dense bordering poison-oak generally keep human entries to his area

to a minimum. Quicksand is prevalent around frequent log-jams and small

natural drop-structures where sediments are deposited rapidly. Depending

upon past storm runoff volumes, quicksand is seldom more than a nuisance

with a resistant base 3 or 4 feet below the surface.

The alder thicket area provides a vital functional role in the

natural working of the marsh system. In addition to the obvious expan­

sion of habitats to include one quite different from those of the marsh

proper, the alder thicket serves as a vital water and sediment buffer.

The thicket area is formed where Butano Creek abruptly turns westward

away from the main trace of the San Gregorio-Hosgri fault as a now-

isolated portion of an ancestral channel. Continued faulting of the

Pigeon Point block upward and northwestward has forced Butano creek to

flow in an extremely low-gradient channel, virtually defeating its sedi­

ment transport capacity locally. To overcome the problems of transport

of its high sediment loads from upstream, the Butano channel has had to

Draft Page 118

aggrade many tens of feet of sand. In so doing, it has lost its conf1n-

ing channel and spread across an area up to 2000 feet wide. Vegetation

in the thicket area is restricted to that which is adapted to frequently

and complete root burial. Adventitious roots now exposed up to 6 feet

above present channel levels indicate that the region has long functioned

to temper the rate of transport of sediment seaward, restraining it at

times of high sediment load and releasing it at times of lower background

transport. The 1982 and 1983 high runoff seasons carried enough new sed­

iment into the marsh area to kill by suffocation most of the older cen­

tral alders of 40-50 years estimated age. This is a natural consequence

of the sedimentation and a pattern that has been repeated many times

judging from the buried and exposed stumps of this short-lived tree

species.

It is recommended that the thicket area be maintained in its present

vital functional role as a sediment buffer and wildlife sanctuary. For

this latter function, it is necessary that it remain continuous with the

present marsh area, and that the passage beneath the Pescadero Road

bridge be maintained. If the thicket were to burn or its vegetation be

functionally damaged in any serious way, the marsh area would be subject

to immediate depositional burial by on the order of 6 feet of sediment

during periods high runoff. outright purchase or lease agreements are

recommended. Loss of this sediment buffering function would certainly

far overshadow any other historic action of mankind that has affected the

marsh system. Restoration cannot be effectively undertaken or maintained

if the alder thicket cannot be secured to a reasonably safe status.

Since the areas of riparian vegetation are subject to annual flooding

Draft Page 119

of the bed of the creek was at least 4-6 feet lower during that period of

time.

It is recommended that care be taken to keep the lower riparian cor­

ridor between the thicket and the bridge clear of log jams. The proposed

management recommendations for the marsh area proper will serve to lower

base level under the bridge and reduce the rate of aggradation, but some

will doubtless continue at times of high runoff floods such as 1955,

1964, and 1982-3. The fine sands that flood out across the agricultural

fields southeast of the bridge are themselves the best long-term solution

to the problem, since these wide natural levees protect against further

flooding while maintaining a fertile agricultural field for annual crops,

or for those that can withstand some degree of sedimentation. The bridge

itself has been raised and replaced at least two times, but the

approaches to the bridge are too low. With reduction in sediment supply

and maintenance of the thicket, the frequency of overbank flooding should

begin to decrease within a few years of implementation of priority one

and two recommendations. Local landowners should be consulted and

cooperative solutions such as cropping adaptations, ditched overbank

returns along the highway, and pressure for County highway improvement

should be mutually considered. Flooding is a natural occurrence here and

will continue to some extent in the future.

~·£·1· Prioriity Three Recommendations

1). ~TERSHED MANAGEMENT PLAN: It is recommended that State Parks consider

initiating a cooperative effort among County agencies, conservation

organizations, and other relevant state agencies to develop and effect a

Draft Page 121

over their entire lateral extent, it is doubtful if the present landown-

ers could successfully convert these sites to any other use. However,

attempts,

effects.

or accidental damage, could have devastating downstream

The current annual overbank flooding problems experienced by lan­

downers along the right bank of Butano Creek in the vicinity of Pescadero

Road are a serious problem. The aggradation of the channel of the Butano

along the East Butane Marsh area and especially upstream into the alder

thicket is such that ordinary average annual discharge will overtop the

stream-banks along the field southeast of the bridge. This overbank flow

will usually pond against the Pescadero Road berm and return to the chan­

nel but in higher (5-year return period flows) it crosses the Pescadero

Road berm and enters the water Lane area fields. Local landowners per­

ceive that this problem of flooding has been increasing in severity in

recent years. Judging by buried fences at the north end of the alder

thicket, and by eyewitness accounts by local people such as camponetti

and Duarte and by the records and opinions of county Road Maintenance

department personnel, 5 to 6 feet of aggradation has occurred in the

vicinity of the bridge since 1955, with the rate of aggradation generally

increasing. This estimate compares favorably with the 4-5 feet of uncom­

pacted sand that we find through coring in this area lying on top of a

layer of coarser clasts over compact organic-rich fine silts. Investiga­

tion in the thicket area and the riparian corridor between the thicket

and the bridge indicates that such periods of aggradation have occurred

before, and to even greater depths than today•s. we also find clear evi­

dence, in the rooting depth of trees 40-50 years of age, that the level

Draft Page 120

general land management plan to reduce sediment production. Such a

cooperative plan should focus on the several areas of primary sediment

production, especially timber harvest, road construction, land clearing,

and some agricultural practices. A specific goal of such a plan should

be the preparation of a map of areas of the watershed that are sensitive

to disturbance in terms of sediment production. This map should specifi­

cally delimit all of the sites subject to gullying, including those west

of Bradley Creek, and those along the Butane creek-San Gregorio fault

valley. Landslide areas with slides that directly enter watercourses

should be outlined for consideration for timber harvest, development, and

road construction. Channel banks subject to undercutting or damaged with

vegetation removal should comprise another map unit. Temporary sediment

storage sites such as the alluvial bottomlands, the alder thicket, and

the finer-grained stream terraces should be inventoried for stored

volumes an susceptibility to releases, and should be mapped.

such a map effort, using aerial photo and field surveys, could be

done cooperatively through the nearby u.s. Geological survey, through

universities, or through other agencies such as the Soil Conservation

service in a period of at most one year. The real effort would then have

to be passed on to county Planning, state Division of Forestry, and the

other land use management agencies for implementation (see Figs. 7 and

8). A goal of s·uch a program should be reduction of sediment yield by on

the order of so percent with existing administrative tools and infras­

tructure. With added effort by the county and state, considerably

greater reductions could be realized. A reduction of so percent in sedi­

ment yield could be translated into a prolongation on the order of

Draft Page 122

several hundred years in the life of the estuarine portion of the

marsh/lagoon system (see for example Rowntree, 1975; Teal and Teal,

1969).

2). NORTH POND HILLTOP: It is recommended that, in the long run, it will be

necessary to do more than just stop the ongoing of expansion of the

current gullies debouching into North Pond. Extensive piping and discon­

tinuous gully segments exist surrounding the hilltop area north and east

of North Marsh. Although grasses are apparently more effective in

preventing gully formation than are pure native brush stands, the best

preventive solution is to maintain a mixed mosaic of brush and grass,

probably fire maintained, with great care taken to avoid compaction by

cattle, roads, temporary vehicle transit, and human trails. To effect

this, it is recommended that the Preserve boundary be extended to the

hilltop.

6.3. Maintenance

The goals of this management plant include, as a major element, full con­

sideration for the establishment of self-reinforcing, "naturally progressing,"

low-maintenance restoration and rehabilitation. However, some maintenance is

inherent in the construction and operation of dikes, devegetation of dune

areas, and operation of tide gates. A particularly difficult area of mainte­

nance, in terms of management strategy, is that of riparian vegetation along

channelways and dikes. The constant dispute between the cost-effective

engineering approach which demands devegetation, and the biologic, ecologic,

and aesthetic approaches that value and favor establishment of undisturbed

riparian corridors is well known. In fact, there are some valid compromise

Draft Page 123

positions. The engineer building a trapezoidal channel to convey water is

concerned with the greatly increased flow resistance of the well-vegetated

channel wall. It is perfectly possible to design the channel to accommodate

slower flowing water with vegetation, but such cannot be justified by most

short-sighted limited cost-benefit analyses. Those concerned with riparian

forest habitat know that many species are propagated primarily by sprouting

from uprooted tree boles carried to new depositional sites by flood waters in

a site where change is a constant. Fish habitat is greatly enhanced by wil­

low, cottonwood, and alder that form a closed canopy over watercourses helping

keep water temperature cool for juvenile steelhead. Landowners see the lean­

ing trees correctly as subject to toppling into the channel and forming log or

debris jams.

For this management plan, it is recommended that design channels be able

to accommodate riparian vegetation, and that its colonization be encouraged.

However, in a natural marsh depositional system, the expected log jams and

overflow breakout patterns create a depositional environment wherein sediment

moves to the lowest areas, fills them, and then seeks another low area. This

means that the natural coastal estuarine-marsh system is one of constantly

changing drainage patterns in its above-tide-range areas. Here at Pescadero,

these are precisely the areas where roadways, bridges, and agricultural lands

abut the Preserve boundaries. To allow the channels in the Preserve to fill

in and shift to new sites, while clearly best from a natural systems perspec-

tive, will wreak havoc with neighbors.

compromise.

It is thus necessary to reach a

It is recommended that existing channels of Butano and Pescadero Creek

leading to the Preserve boundaries and leading downstream to a channel bed

Draft Page 124

elevation of approximately 6 feet above msl, be maintained for open flow.

This does not mean that highwater overflow of water and sediment is not to be

encouraged wherever possible. The operative strategy should always be to

allow streams to deposit sediment loads over as large an area as far from the

marsh and lagoon as possible. However, to maintain the positions of the

channels leading to the State's lands, some effort must be made to preserve

the upper channels within the Reserve proper. To this end, the hand removal

of existing log jams and leaning trees (greater than 20 degrees from vertical)

is in order. The very marginally gravel-armored bed of Pescadero Creek where

it enters the Preserve boundary and above it should not be disturbed if at all

possible. Use of chainsaws to reduce logs to 5-foot lengths that can be car­

ried out on tidal or runoff floods should in most cases be adequate. The

existing log jam near Round Hill that has not been completely removed by burn­

ing in the past is at a low enough elevation to pose no serious threat to

private lands, but may trap logs cut and left in place upstream. some con-

sideration may then be given to reducing its right (main) channel blockage by

sawing.

For sites above the Preserve boundaries, consideration should be given to

use of state ccc crews working with local landowners and a "streamwatch" pro­

gram where local people could call and ask for help with log removal. Because

of the sediment source implications of upstream logjams on both Pescadero and

Butane creeks, it is recommended that the state take an active role in logjam

removal and prevention. such activities are clearly part of the maintenance

responsibilities necessary to operate the Preserve effectively.

Other maintenance tasks inherent in the before-listed recommendations

(sections 6.1 and 6.2) include careful maintenance and monitoring of any in-

Draft Page 125

gully erosion control structures. Filter blankets and cribbing can do mor8

harm than good if they are not maintained and observed after every major

storm. The overflow channel at the "big bend" on Pescadero creek and its

accompanying wing dike must be maintained in an operating condition. The East

Butane Marsh overflow channel, as recommended, will probably fill with sedi­

ment after major flood flows. Bulldozer access to this site should be main­

tained as at present. Effective trapping of sediment in the East Butane marsh

area may lead to infilling of some or all of the vernal pools there. These

three features are clearly show on the 1854 map and all later aerial photos.

Very modest earth moving in the easternmost portion of this marsh segment

could encourage sediment deposition in such a fashion that the permanence of

these pools was enhanced.

Highway maintenance crews regularly remove sand from Highway one where it

is blown. This sand should be returned to the beach circulation cell by dump­

ing it at the north end of the state Parks beach parking area.

!!_._!. Timing

Timing the period of alterations is crucial to the success of the res­

toration plan. Major disturbances of dikes and vegetation should not be per­

formed immediately prior to the rain season, setting a scenario for extensive

erosion. Alterations to the marsh should be temporally spaced, distributing

impacts across time and insuring the stability of the ecosystem.

!1.·1· Monitoring Program

Restoring a major system like the Pescadero Marsh is not a simple

single-effort task. It requires careful observation once alterations begin

Draft Page 126

and historical flow patterns are restored. such monitoring warns of adverse

effects and events, and judges restoration progress relative to the plan,

while collecting further information necessary to enhance our understanding of

processes active in the marsh. To the extent that monitoring can provide

this, greater effort should be directed toward it and the public can be

assured that its money is well spent.

~·~·!· Progress

Performance standards once established, should be utilized to monitor

activities in the beach zone, marsh zone, and upper watershed so impacts con­

flicting with the objectives of this restoration plan will be indicated.

Accordingly, progress of the restoration program can be judged and the marsh

can be protected from the adverse effects of activities occurring within the

watershed.

A number of techniques can be employed as part of a monitoring program.

The following should be considered.

(1} Flow and Discharge Gauging

The quantities of water flowing into and out of the wetlands define the

character of the marsh. In order to more adequately model the hydrologic

regime of the wetlands, the determination of flows is a minimum of infor-

mation. such information is essential to managing the system and deter-

mining appropriate times for beach berm breaching.

(2} Chemical water Quality (surface and groundwater}

Obviously, water quality is critical to the productivity and persistence

of the wetlands. Monitoring water quality should be a top priority to

Draft Page 127

insure the success of any restoration project. surface water sampling

should be performed seasonally in order to determine the full range of

values for a particular constituent. This could be adequatedly achieved

by sampling at the end of summer (prior to and at the initiation of the

winter rains) to determine the maximum levels of contamination; and again

at the end of the winter rains to determine the levels of contamination

following extensive flushing. water quality should be monitored for

sea-water intrusion, urban and agricultural runoff, domestic waste and

landfill leachates, and erosion and sedimentation by analyzing for the

following constituents:

salinity lead and other heavy metals nutrients pesticides landfill leachates (acidity) sediment discharge sedimentation turbidity

(3) Population Transects

Population transects can be a convenient technique for monitoring long-

term trends in ecosystems. While such a technique is quite interpreta-

tive, it is valuable to the extent that species patterns tend to

integrate the extent of events and activities occurring within the habi-

tat. Biological conditions stand as the prime criteria by which restora-

tion can be judged. Accordingly, permanent transects should be esta-

blished deriving species composition, population densities and coverage

with sampling at various elevations and flow regimes of the following:

vegetation fisheries birds

Draft Page 128

mammals reptiles

(4) Aerial Photography

The bulk of historical information available on the Pescadero Marsh has

been derived from aerial photography, As such, these photos provide the

baseline values for conditions in the marsh. To assess large scale

effects resulting from alterations in the Marsh, aerial photography

should be employed and compared against existing photography.

6.6. Upper watershed Recommendations

As has been expressed repeatedly, any effective restoration of the Pes-

cadero Marsh is dependent upon managing land uses in the upper watershed which

significantly impact the character of the marsh. However, difficulties arise

in attempting to implement such influence given the limited jurisdiction of

the state Department of Parks and Recreation. Despite this impediment, it is

recommended that watershed management be approached. Given the diverse

interests involved in the handling of the Pescadero Marsh, this may provide an

ideal opportunity in which to institute such a program.

~·l· Justification !2£ Growth control

The most critical adverse land use affecting wetlands is intensive urban

development not simply due to the panoply of direct impacts but to the long

term commitment of resources and the persistence of structural features. Such

impacts include:

Draft Page 129

(l) roads and bridges serving urban development presently impinge upon the

marshland by confining its expanse and flow patterns;

(2) competition for limited resources particularly in the flatlands reduces

the quality of water and land available to agriculture and the marsh;

(3) disposal of domestic wastes threatens water quality in the marsh;

(4) grading of surfaces for construction disturbs soils and vegetation which

increases erosion and sediment input to surface waters;

(5) impermeable surfaces resulting from urban development (paving, building

construction, etc.) reduce infiltration and increase runoff downstream,

thereby:

-increasing erosion and sedimentation in lowlands, -increasing flood peaks and risks downstream, -reducing groundwater recharge.

Once development in an area is established its progress is seldom

reversed, especially along the central Californian coast. Consequently, such

development frequently translates into a lost opportunities for wetlands res-

toration. Persistence and productivity of a unique wetland system can be most

effectively achieved by intercession prior to degradation approaching a criti-

cal state. The Pescadero creek watershed is at an appropriate stage to con-

certedly manage existing land-uses, preempting the introduction of land-use

patterns and practices which are incompatible with the persistence of a coa-

stal wetlands systems. Preventive measures taken are far more efficient and

effective than attempts to obtain a cure. However, certain preexisting condi-

tions in the watershed would render the application of preventive measures

meaningless •. Accordingly, corrective measures must be taken where adverse

effects have and are occurring.

Draft Page 130

~·l·l· Recommendations 1£ control growth ~ urban development

Controlling urban development and growth along the coast of California

has become rabid political game during the past decade with the most prominent

result being the California coastal Act of 1976. These efforts have been

directed primarily at regulating land uses by the review of local master

plans. such efforts have proven to be quite confrontational and not wholly

successful. While the use of zoning regulations should not be ignored, what

may prove to be more effective is the control of infrastructural development

upon which urban growth is dependent. The control of infrastructural develop­

ment would primarily regulate the construction of roads, sewers, and water

supply projects. Controlling convenient access by limiting the improvement of

existing roads and the construction of new roads, controlling the capacity for

waste disposal to natural, local constraints by limiting sewer projects, and

controlling water availability by limiting water supply projects will, at a

minimum, maintain the demand for residential development in this area. Fail­

ing to implement these controls will surely induce urban development and its

attendant impacts. such controls should be implemented in addition to zoning

for conservative land use that is traditional to the region.

~·~· Institutional Arrangements

~·~·l· Special Legislation ~ Sensitive Habitat Designation

Given the unique character of the coastal wetlands of Pescadero Marsh and

the inherent dependence of the marsh upon the character of the entire

watershed, consideration may be given to special legislation designating

watersheds upstream from sensitive habitats as correspondingly sensitive.

such designation would require special permitting and review of activities

Draft Page 131

within the watershed including:

-Timber Harvest Permit review:

this would require exception to existing state legislation to allow

local review of timber harvest permitting process, giving special atten­

tion to assessment of slope stability, erosion potential, and stream

protection zones;

in addition, measures should be taken to insure conformance with per­

mits.

-grading permit review,

-riparian habitat protection zone,

-erosion control ordinances.

Considerations may also wish to be given to development of legislation to

correct the North Pond circulation problem through culvert construction.

~·~·~· watershed Agency

Additionally, the permitting process for any given activity should be

efficient for both the administrating agency and the applicant. Duplication

and multiple permitting should be avoided, not only for the sake of effi­

ciency, but also to remove the bureaucratic disincentives. To the extent that

the process is convenient, the cooperation of residents is encouraged.

Accordingly, the permitting process should be integrated into a single

clearinghouse-type agency with regulatory powers vested to them by member

agencies. While having the potential for streamlining the permitting process

and providing consistent information, such an agency would have the inherent

ability to assess the cumulative impacts of all activities within the

watershed by virtue of being the sole responsible agency. said agency might

Draft Page 132

consist of those existing agencies and interested parties presently affiliated

to the Pescadero Marsh and activities in the watershed: Parks and Recreation,

Fish and Game, Forestry, county Planning, sequoia Audubon, open space, etc.

REFERENCES CITED

Addicott, W. o., 1952, Ecological and natural history studies of the genus

Macoma in Elkhorn Slough, California. M.s. thesis, Stanford Univ. 89 p,

Angeloni, W. C., 1984, Letter report of April 5 to A. E. satow, state of Cali­

fornia, Dept. of Transportation, Dist. 4, san Francisco of hydraulic com­

putations and computer analyses of 4 possible bridge alternatives to

replace Pescadero Bridge. Dept. of the Army, san Francisco Dist., Corp

of Engineers, 3 p.

Atwater, B. F., and C. W. Hedel, 1976, Distribution of seed plants with

respect to tide levels and water salinity in the natural tidal marshes of

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_______ , and E. J. Helley, 1977, Late Quaternary depositional history, Holo­

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Bergquist, J. R., 1978, Depositional history and fault-related studies, Boli­

nas Lagoon, california. u.s. Geol. Survey Open File Rept. 78-802, 227 p.

Brewer, w. H., s. Watson, and A. Gray, 1876, California Geological Survey, v.

1, Botany. welsh, Bigelow & co., Univ. Press, Cambridge, Mass, 628 p.

Draft Page 133

Brumunel, G., 1939, Bridge Dept. -Preliminary Report- Proposed Bridge across

Pescadero Creek located 28 miles south of Half Moon Bay in San Mateo

County, IV-SM-56-B, Bridge No. 35-28, July, 1939, unpaginated.

California Coastal Commission, 1982 (to be supplied by T. Taylor

deleted)

California state Highway Dept., 1939, (see Brurnunel, 1939).

else

_______ , 1941, Bridge construction Report, Pescadero Creek Bridge, No. 35-28.

Typescript on file, CalTrans Offices, Dist. 4, san Francisco. Plates,

photos, and drawings.

Clark, J. c. and E. E. Brabb. 1978, stratigraphic contrasts across the San

Gregorio Fault, santa Cruz Mountains, West central California. pp 25-34

in Calif. Div. Mines and Geol. sp. Rept 137. Dept. of Water Resources,

1959, california floods of~· State of California, sacramento, Calif.

Corps of Engineers, u.s. Engineer Dist., 1969, water Resources Development,

Interim Survey Report, Pescadero Creek, Dec. 1969, san Francisco, 42 p.

in App, A- hydrology,

_______ , 1984, (see Angeloni, 1984; Wisney, 1984).

Curry, R. R. and G. M. Kondolf, 1983, Sediment transport and channel stabil-

ity, Carmel River, california. Rept. to the Monterey Peninsula water

Management District, Monterey, Calif., 400+ p,

Elliot, Bruce, 1973, The Natural Resources of Pescadero Marsh and Environs.

California Department of Fish and Game Draft Coastal Wetland Series #13.

July 1975.

Draft Page 134

FEMA, 1982, Flood Insurance study, san Mateo county, calif., Unincorporated

Areas. Federal Emergency Management Agency, community Number 060311, 480

map panels + text and profiles 16-P through 20-PP (Pescadero).

Frenkel, R. E., 1978, Ruderal vegetation along some California roadsides:

Univ. Calif. Publ. in Geog., v. 28, 163 p.

Glen, W., 1959, Pliocene and lower Pleistocene of the western part of the San

Francisco peninsula. Univ. calif. Publ. Geol. sci. Bull., v. 36, p.

147-198.

Heyes, D. G., 1977, A geotechnical study of Lower Pescadero creek, San Mateo

County, California. state of california, Dept. of Transportation,

Materials Section, San Francisco. 48 + p.

_______ , 1981, Update of March, 1977, Geotechnical report on the mouth of Pes­

cadero creek (including the project to remove rocks and pilings). state

of California, Dept. of Transportation, Materials Section, Dist. 4, San

Francisco, 30 + p.

Hicks, s. D., 1968, Long-period variations in secular sea level trends. Shore

and Bech, v. 39, no. 1, p. 26-31.

Johnson, J, w., 1971, The significance of seasonal beach changes in tidal

boundaries. Shore and Beach, v. 39, no. 1, p. 26-31.

Josselyn, M. (ed. ), 1982, Wetland restoration and enhancement in California.

Tiburon Center for Environmental Studies, Calif. Sea Grant Rept. No. T­

CSGCP-007, December, 1982.

Draft Page 135

Kinney, A., 1895, Eucalyptus. B. R. Baumgardt & co., Los Angeles, 298 ~·

LaJoie, K. R. and others, 1979 Quaternary Tectonics of coastal santa ~ and

~ ~ counties, california, ~ indicated ~ deformed marine terraces

~alluvial deposits (with other papers); pp 61-119 in weber, G.E. , et

al, (eds), Field Trip Guide, coastal Tectonics and coastal Geologic

Hazards in santa cruz and san Mateo counties, California; cordillerian

Section, Geol. Soc. America.

Milliman, J. D., and K. o. Emery, 1968, sea levels during the past 35,000

years. Science, v. 162, p. 1121-1123.

Nichols, D. R., and N. A. wright, 1971, Preliminary map of historic margins of

marshlands, San Francisco Bay, California. u.s. Geol. Survey Open File

Rept., 10 p, 1 map 1:125,000

Pierce, J. w., 1970, Tidal inlets and washover fans. Jour. Geo1., v. 78, p.

230-234.

Rantz, s. E., 1971, Mean Annual Precipitation Depth-Duration-Frequency data

for the San Francisco Bay Region. u.s. Housing and Urban Development and

u.s. Geol. survey Basic Data Contribution 32, san Francisco Bay Region

Environment and Resources Planning study series, map + text.

Rowntree, R. A., 1973, Morphological change in a California estuary: Sedimen­

tation and marsh invasion at Bolinas Lagoon. PhD dissertation, Univ.

Calif. Berkeley, 271 p.

Draft Page 136

_______ , 1975, Morphological aging in a California estuary: Myth and institu­

tions in coastal resource policy. Geoscience and Man, v. 12, p. 31-41.

san Mateo County Planning Dept., various dates, Photogrammetric maps of Pes­

cadero Lagoon area. Three map series are available at very large scale

for the 6 sheets covering the lagoon/marsh area.

Scholl, D. W., F. C. Craighead, and M. Stuiver, 1969, Florida submergence

curve revised: Its relation to coastal sedimentation rates. Science, v.

163, p. 562-564.

Shalowitz, A. L., 1964, Shore and sea boundaries, interpretation and use of

coast and Geodetic Survey data. u.s. Dept. commerce, coast and Geodetic

survey, wash. D.C., v. 2, 749 p.

Simons, D. B., 1984, Report on causes of flooding of the Phipps property in

Dec. 1977, Pescadero, California. Simons, Li and Associates, Ft. Col­

lins, Colorado, unpaginated.

swanson, M., 1982, Piping and gully formation in coastal san Mateo County,

california. Master of science thesis, Dept. of Earth Sciences, Univ.

calif., santa cruz.

Teal, J, and M. Teal, 1969, Life and death of a salt marsh. Ballantine Books,

New York, 274 pp.

Violis, F., 1979, The Evolution of Pescadero Marsh. Master's thesis, Dept. of

Geog., San Francisco state Univ.

Draft Page 137

Weber, G. E. and K. R. LaJoie, 1977, ~Pleistocene and Holocene Tectonics

of the ~ Gregorio Fault ~ between Moss Beach ~ Point Ano Nuevo,

~~Co., calif. Geol soc. America Abs. with Programs, v. 9, no. 4,

p. 524.

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Geol., v. 43, no. 2, p. 273-310.

Wisney, P. B., 1984, Hydraulic Evaluation, Pescadero Creek Bridge Replacement.

State of Calif., Dept. of Transportation, Dist. 4, san Francisco. Sept.

11, 15 p.

Draft Page 138

Pescadero study Hydrologic Bibliography

Doyel, w. w., et al, 1967, Index to: catalog of information 2rr ~ ~' surface water stations. Dept. of the Interior, Geological survey, Office of water Data Coordination, Washington, D.C.

Fiering, M. B., 1967, stream~ synthesis. Harvard University Press, Cam­bridge, Mass.

, and Jackson, B. B., 1971, synthetic streamflows. American Geophysi­cal Union, Washington, D.C.

Goss, Joseph, 1974, Availability £f ~ 2rr surface-water quantity and quality ~ the ~ Francisco bay region, California, with ~ summary of beneficial uses and implications for land ~· Interpretive Report 5, Dept. of the Interior, United states Geological survey, Washington, D.c.

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Draft Page 140

Interior, Washington, D.C.

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Draft Page 142

APPENDIX l

PESCADERO MARSH PRESERVE ACREAGE*

UPLANDS North Lands (includes dunes, eucalyptus grove, coastal Terrace Field east of Round Hill Nunziatti Hill Nunziatti Field Round Hill Dikes

uplands Total

WETLANDS North Pond North Marsh Delta Marsh East Delta Marsh North Butane Middle Butane East Butane Lagoon and River Channel

wetlands Total

Preserve Total

123.62 etc. 59.00 7.01

25.73 7.86 3.42

40,91

267.55 acres

17.30 65.12 82.45 44.80 30.85 11.92 49.39 18.50

320.33 acres

587.88 acres

*Areas determined from CalTrans aerial photograph taken June, 1980. (scale 1:6000)

Draft Page 143

APPENDIX 2 - Pescadero creek Flow Frequency Analysis

U. c. santa Cruz - Log-Pearson Type III--Frequency Analysis - Version II Fluvial Systems - Spring 1983 Page l

Pescadero-Creek-near-Pescadero 1951 TO 1982 N = 32 STATION 11126500 CODE PK

INPUT DATA

65.000 3360.000 3440.000 953.000 840.000 9420.000 908.000 7630.000 1380.000 816.000 150.000 1720.000 6700.000 1170.000 3310.000 626.000 4100.000 2740.000 2900.000 2300.000 770.000 205.000 5380.000 2370.000 1740.000 86.000 67.000 4060.000 1900.000 2940.000 631.000 9400.000

MEAN LOGS = 3.143 STANDARD DEVIATION LOGS = .599 SKEWNESS LOGS = -.873 STANDARD ERROR OF SKEWNESS LOGS = .414 EXCEEDANCE PROB RECURRENCE INTERVAL MAGNITUDES

.9900 1.01 24.155

.9500 1.05 107.972

.9000 1.11 219.648

.8000 1.25 479.493

.7000 1.43 799.016

.5000 2.00 1694.536

.4000 2.50 2341.747

.2000 5.00 4516.414

.1000 10.00 6805.727

.0400 25.00 9822.469

.0200 50.00 12013.735

.0100 100.00 14084.741

.0050 200.00 16015.228

Draft Page 144

u. c. Santa cruz - Log-Pearson Type III--Frequency Analysis - Version II Fluvial Systems - Spring 1983 Page 2 Pescadero-Creek-near-Pescadero 1951 TO 1982 N = 32 STATION 11126500 CODE

PK

0.995 0.99 0.95 0.90 0.80 PROBABILITY

0.50 0.20 0.1 0.04 0.02 0.01 0.005

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1.005 1.01 1.05 1. ]_]_ 1.25 2 RECURRENCE INTERVALS

THE FOLLOWING SYMBOLS MAY APPEAR IN THE PLOT X - AN INPUT DATA VALUE

* - A CALCULATED VALUE 0 - A CALCULATED VALUE AND ONE DATA VALUE AT SAME

POSITION 2 - TWO INPUT DATA VALUES PLOTTED AT SAME POSITION 3 - THREE INPUT DATA VALUES PLOTTED AT SAME POSITION A - A CALCULATED VALUE AND TWO DATA VALUES AT THE

SAME POSITION

B - A CALCULATED VALUE AND THREE DATA VALUES AT THE SAME POSITION

Draft

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Page 147

PescaFile XlFile = sanL5160 XlFile = Sarat5160

YFile = Pesca5160

0. 94101997 = Req -2.90046593 =bO

0.21697967 =b1 1.99461177 =b2

===== PescaFile ==::;= === 1== is interval

2=== is interval === 3=== is interval

4=== is interval --- 5=== is interval === 6=== is interval === 7=== is interval === B=== is interval === 9=== is interval ===10=== is interval ===11=== is interval ===12=== is interval

APPENDIX 3

HYDROLOGIC DATA SUMMARY

0 <= discharge < 5 === 1== 5 <= discharge < 10 == 2===

10 <= discharge < 50== 3== 50 <= discharge < 100 === 4===

100 <= discharge < 200 === 5=== 200 <= discharge < 500 === 6=== 500 <= discharge < 1000 === 7===

1000 <= discharge < 2000 === B=== 2000 <= discharge < 3000 === 9=== 3000 <= discharge < 4000 ==10=== 4000 <= discharge < 5000 ===11=== 5000 <= discharge < 10000 ===12===

===13=== is interval 10000 <= discharge < 9000000 ===13===