Larsen Creek Stream AssessmentLagunitas Watershed, Marin County

Brian BelluominiBill GoedeckeParis Good-SwanThad SheltonOscar Steiner

G642 Watershed RestorationFall 2009

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(SPAWNUSA)

Introduction

The Lagunitas Creek Watershed in Marin County is one of the most

important spawning sites for Steelhead trout and Coho salmon in California.

Larsen Creek is a tributary in the watershed that has some of the ideal

structures necessary for fish spawning, such as pool - riffle channel

characteristics. One study was completed on Larsen Creek to assess the habitat

conditions for fish but no data existed about the spatial layout of the creek. The

purpose of our study was to complete a structural survey of Larsen Creek to

determine future restoration options and fish habitat analysis. These can be

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compared with future measurements to determine the success or failure of

restoration and erosion control practices at maintaining a pool-riffle channel. A

recent study (2005) showed that the Larsen Creek was one of the most

successful streams in the watershed at providing habitat for salmon and trout as

they left for the ocean. Our study shows that with some strong erosion control

methods, Larsen Creek can continue to be an ideal habitat for Coho salmon and

steelhead trout.  

Larsen Creek Watershed

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Stream Description

     Larsen Creek is located in the Lagunitas Creek watershed in West Marin

County, California. It is a first order stream that flows into San Geronimo Creek.

About half of the land surrounding the Lagunitas Creek watershed is privately

owned.  The other half is dived between the Marin Municipal Water District and

the National Park Service (NOAA 2008). The housing density in this watershed

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is relatively sparse with only 6,000 residents and 2,600 houses on about 70,000

acres.

Ownership map of land in Lagunitas Watershed (SPAWNUSA)

Larsen Creek was chosen for its ease of access and its function as historic

salmon habitat. According to SPAWN, the tributaries of San Geronimo and

Lagunitas Creeks have higher rates of salmon spawning and juvenile habitat

areas than the main creek itself. This was a deciding factor in choosing this site.

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Chart comparing rates of redds per stream area in the Lagunitas Watershed. Spawning density is higher in the smaller tributaries. (SPAWNUSA)

San Geronimo Golf Course (LagunitasMontessori.org)

The San Geronimo Golf Course, located to the North and East of our study

area, is one of the biggest stakeholders of Larsen Creek. Much of the upstream

reach flows directly through sections of the golf course. Adjoining the

downstream areas of Larsen Creek is a school and community center to the

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West and a County-managed open space preserve to the East that is frequently

used by hikers, bikers, and equestrians. The size of the watershed that drains

into Larsen Creek is approximately 465 acres. The confluence of Larsen and

Geronimo Creek is approximately 76.2 meters and the elevation in the

headwaters area is approximately 213.36 meters (Reese et al. 2005).

Impervious surfaces are primarily in the lower reach area. Sir Francis

Drake Road is a major thoroughfare that runs roughly parallel to San Geronimo

Creek near the Larsen and San Geronimo Creek confluence. The Lagunitas

School is located on either side of the lower reach and is composed of two

campuses connected by a paved road that crosses Larsen Creek approximately

292 meters from the confluence (measurement by Reese et al. 2005). Total

acreage for the amount of impervious surface for both campuses and the

Lagunitas School Road is approximately 7.2 acres with 2.3 acres draining

directly into the creek through a culvert on the east side of the creek.

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Using Rosgen Stream Classification, the first 200 or so meter stretch of

Larsen Creek from the confluence with San Geronimo Creek is a B6 channel

type. The next 500 or so meter reach is a F3 channel type. No classification

was done above this point. (Reese et al. 2005). A F3 channel has a riffle/pool

morphology with infrequently spaced pools, a high width to depth ratio and is

entrenched, meanders and is mostly dominated by cobbles (Rosgen 1994).

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Above the Lagunitas Bridge and up to the golf course Larsen Creek can be

characterized as more highly incised with a slightly greater stream gradient than

below the bridge. Less sediment was observed in the creek bed in the upper

channel than was observed in the lower channel. A B6 channel also has a

riffle/pool morphology and a high width to depth ratio but with less

entrenchment (Rosgen 1994). It is noted for having infrequently spaced pools,

although the stretch we surveyed was more pool dominated due to the presence

of two culverts that act as drainage for adjacent areas. More sediment

deposition was observed in this lower reach. The substrate is often sand and silt

or clay. Larsen Creek looked to adjust into a class B channel with progressively

lower banks as the creek meanders into the valley bottom.

 

Stakeholders and Watershed History

The main stakeholders for Larsen Creek are the San Geronimo Golf

Course, Lagunitas School, residents that live along San Geronimo Creek, and

SPAWN (Salmon Protection and Watershed Network). The golf course owns

much of the land that the Larsen Creek runs through as well as some of the

tributaries that flow into it (Reese et al. 2005). The course manager seems to be

impartial to the condition of the creek so long as it looks good for golfers and

restoration attempts do not affect the layout of the golf course. The Lagunitas

School greatly wants to preserve the delicate stream habitat so that the children

of the school can enjoy its beauty and observed the endangered salmon that

spawn in its waters. Some of the residents living along San Geronimo Creek and

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SPAWN have somewhat differing views (personal communication with SPAWN

founder, Todd Steiner).

 SPAWN recently sued the county of Marin for not acting on their promise

to improve stream quality and building regulations, which forced the county into

a two-year moratorium on building within 100 feet of any stream (SPAWN 2009).

A local community meeting was held with the county supervisor, SPAWN and

concerned community members. Members of the community were concerned

that the value of their homes might be affected, that they would not be allowed

to have gardens and other modifications along the creek corridor, and that local

construction business might be hampered. SPAWN argued that preserving the

creek and endangered species that live in it will increase the value of property

located on the creek and will improve the water and habitat quality by

preventing development, making the stream a safer place for children to

explore. Not surprisingly, residents support stream restoration so long as it

doesn’t affect them directly. Many residents are very hostile towards SPAWN

and its volunteers because they think that SPAWN will report their creek-side

activities, resulting in a fine by the County or forced removal of their private

structures. This makes access to the San Geronimo creek more difficult than it

may have been before the moratorium. SPAWN has attempted to modify the

way people interact with the stream in order to try and rehabilitate the riparian

habitat, water quality, and abundance of spawning fish. If the stream quality

degrades to the point where no fish return, SPAWN will have a harder time

finding funding and inspiring the community to help in the preservation and

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restoration of the streams (personal communication with SPAWN founder, Todd

Steiner).

Previous Studies

    A previous study of Larsen Creek was completed in September of 2005. It

was done by the Watershed Stewards Project/AmeriCorps Members under the

influence of the California Department of Fish and Game. The goal was to

determine what habitat was available for anadromous salmonids (Reese et al.

2005). They also made recommendations for habitat improvement. At the time

of the study there were two culverts pouring into Larsen Creek causing

substantial bank scouring. This is still an issue today as the pools formed by the

culverts are quite deep and channelized flow is causing substantial bank

erosion.

The 2005 study completed a habitat inventory that was found in the

California Salmonid Stream Habitat Restoration Manual and the components

researched were flow, channel type, temperature, habitat type, embeddedness,

shelter rating, substrate composition, canopy, bank composition and vegetation,

large woody debris count, and average bankfull width. However, missing from

this study was a detailed physical profile of the stream.  This project therefore

focused on creating a detailed spatial profile and sediment analysis of Larsen

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Creek by creating a sound longitudinal profile, three cross section studies, and a

detailed pebble count of the downstream reach of the creek. This analysis will

be helpful in future comparisons to determine if restoration methods are

actually succeeding in reducing erosion and creating suitable salmon and trout

habitat. The study from 2005 found that B6 and F3 channels are especially

strong places for salmon habitat.

Salmon returning to San Geronimo Creek in 2008 (SPAWNUSA)

Cover created by boulders and logs are safe places for fish to hide from

predators and the structure of the channel is good for restoration methods and

streambed enhancement (Reese et al. 2005). The embeddedness of Larsen

Creek and the extensive woody debris around the stream also create well-suited

areas for spawning. Wood structures protect salmon from predators, provide

places for resting and reduce competition for food and shelter. Many

recommendations were made in the 2005 study including completing an

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inventory of stream bank erosion, identifying sediment sources, increasing

woody cover on the pools and designing pool enhancement structures.

 

Salmon

     The Lagunitas Creek Watershed sustains the most significant population

of endangered Central Coast Coho salmon in California (Pincetich 1999). This

watershed supports 35 miles of Coho-bearing streams. Coho salmon have a

three year life cycle.   Their first year is spent living in rivers and streams before

migrating to the ocean for a year and a half.  They need substantial food,

protection, and cool, well-oxidized water in order to survive the first year of life

(Flosi et al. 1999). The streams of California generally have enough gravel for

spawning but there are not enough streams with pools for the juvenile Coho.

The juveniles prefer slow moving water with a temperature between 48 to 60° F.

Coho in the early stages of their lives need access to shallow, calm water and

the California Salmonid Stream Habitat Restoration Manual recommends that

restoration projects should focus on providing shade, woody debris, and organic

nutrients to ensure suitable habitat (Flosi et al. 1999). Larsen Creek has a well

developed pool and riffle system and is also a cold-water stream away from

many of the negative effects of urbanization, making it a good site for salmon

spawning. There is also extensive canopy cover that keeps the stream cold in

the summer months.

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The Central California Coast ESU Steelhead is also a threatened fish

species that lives in the Lagunitas Creek Watershed. Steelhead trout enjoy more

streams and areas of suitable habitat than the Coho salmon, and the steelhead

are much generally more flexible with their living conditions (Pincetich 1999).

Over a lifetime, they can make several spawning trips between the ocean and

freshwater and actually spawn later in the winter or in early spring. Steelheads

often spend more than a year in freshwater before migrating to the ocean,

allowing them to grow larger and thus having a greater likelihood of survival.

The preferred habitat of the steelhead is very similar to the Coho. Small gravel is

necessary for spawning and logs and boulders will greatly improve habitat

conditions (Flosi et al. 1999). Juveniles also prefer to live in shallow pools or

riffles where the water is cool.

    A study done in the spring of 2009 researched the amount of salmon in

the Lagunitas Creek Watershed that were returning to the ocean (Pincetich,

2009). 48 Coho smolts were observed in Larsen Creek this year, almost double 14

the amount observed in previous years. A total of 664 smolts were observed in

the entire Lagunitas watershed. This is a very promising number because very

few smolts were found in the past several years due to drought and barriers to

out-migration. Bank restoration and erosion reduction methods will increase the

likelihood that Larsen Creek can remain a strong site for salmon populations.

Erosion Potential (SPAWNUSA)

     The presence of salmon in a stream is an indicator of overall stream

health. Besides providing a profile of the physical structure of the stream, the

goal of our study was to determine if Larsen Creek is providing ideal habitat for

salmon. Previous restoration projects and the amount of erosion and sediment

needed to be analyzed in order to determine the feasibility of a salmon habitat

in Larsen Creek. The sides of the banks in several areas looked like they had

undergone bank stabilization projects in order to reduce the amount of erosion

taking place. The 2005 study recommended bank stabilization projects as the

best way to reduce erosion but unfortunately these projects had failed and the

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bank continued to erode past the roots of the trees. It is important to determine

the amount of erosion and sediment in the stream because this could affect the

stream composition and reduce the likelihood of salmon using Larsen Creek to

spawn in the area of our survey.

Evidence of streambank erosion

    

Survey

In September and October of 2009, our group completed three cross-

sections, three pebble counts, and a longitudinal survey of a downstream reach

of the creek. On the first visual assessment of the streambed, the stream was

relatively dry with no flow in the ripples but some standing water in the scour

pools.  The second visit to the streambed was after the first significant rain of

the season and there was flow through the thalweg and significant water depth

in the pools. On the third visit, the stream still had water flowing throughout the

length of the reach despite there having been no rain in between visits.

Significant woody debris and canopy cover were observed, indicating good

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areas for salmon habitat. However, substantial bank erosion was also observed

occurring throughout the length of the reach.

 Access

  Our study area is located on the property of a public school, adjacent to

public access off of Sir Francis Drake Boulevard, and within the boundaries of

the Marrietta Larson Preserve.   There were no stakeholder protests in surveying

the site, and there was easy access from the public parking area next to the

public school and San Geronimo Community Center.  Upstream of the study

area, Larsen creek runs through a section of the San Geronimo golf course.  

Contact was made with managers of the golf course and permission was

granted to access the section of the creek that runs through the course for up-

stream reconnaissance. Larsen Creek has no access obstacles (other than

widespread poison oak) and this is unlikely to change in the near future.

Methods and Materials 

     Our assessment of the lower stretch of Larsen Creek relied mainly on

creating an approximation of the physical structure of the stream by surveying a

longitudinal profile and three creek cross sections.  Other features of the creek

that have an impact on streamflow, erosion and sediment yield, such as culverts

and previous restoration sites, were documented and given impact analysis. 

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Equipment used: 

Leica Sprinter 100 digital leveler Stadia rod Increment tree borer Trimble GPS receiver Suunto tandem combination compass/clinometers 50 m measuring tape Field Notebooks

Excepting the camera, all data collection equipment was borrowed from the SFSU Geography Department with permission from Dr. Jerry Davis.

The Leica Sprinter and Stadia rod in action

Fieldwork Dates (2009):

  September 26th - site selection, reconnaissance

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  October 17th - First day of assessment and field work, longitudinal

profile

  October 30th - Pebble count, cross section measurements, flow

   October 31st - Pebble count, cross section measurements, flow

Field data collection was done primarily using a Leica Sprinter digital

leveler.  To create our survey, a permanent benchmark was created at the SE

corner of the bridge spanning Larsen creek at the upstream boundary of our

survey area.  This was our primary control point as it is permanent and visible

from the majority of our study area. 

Established benchmarks

To begin our analysis of the creeks morphology, we needed to establish a

permanent benchmark, at a fixed location, by which to measure or elevations

from. A small bridge crossed the creek at the most upstream extent of our

survey. The footing of the abutment (BM1) provided a stable foundation to fix

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our vertical control. We set up the Leica Sprinter on a point bar at the first

meander of the creek. This location was recorded by backsighting to BM1 and

fixing our instrument height at .099 m. above the footing and 10.71 m distance

@ 36.5 degrees azimuth. During the longitudinal profile, the instrument had to

be moved twice in order to maintain stadia rod visibility. During each move, the

foresights and backsights were recorded and monitored with secondary support

from clinometers to reinforce the azimuth. (see Longitudinal Profile Spreadsheet

(LPS) for data)

To survey the longitudinal profile, a tape measure was laid in the creek

along the thalweg and station distances were calculated at every 0.5 m.  The

average width of the channel is estimated to be 3 meters; thus the longitudinal

profile, being 20x channel width, spanned 60 meters of the creek.  Because of

areas of fallen trees and dense vegetation, it was necessary to create turning

points within the survey.  Included in the profile were recordings of water depth

and substrate materials as well as major creek features such as pools/riffles,

fallen vegetation, bank erosion and culverts. 

Cross sections were surveyed at several locations along the

stream. Significant trees with a small nail driven into the trunk were established

as controls. These also served as new benchmarks, as each was referenced to

BM1 and recorded as BM2, BM3 and BM 4, respectively. Height, distance and

azimuth were recorded for these locations. (see LPS) The measuring tape was

stretched across the stream perpendicular to stream flow. A second measuring

tape was maintained along the thalweg to cross-reference the longitudinal

profile with the x-section and the station id. The cross section profile along with

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measurements of streambed and streambank characteristics and water

conditions were observed and recorded. Cross section locations were chosen to

give a representative idea of the valley shape and to ensure easy replication of

the survey in the future.

A pebble count was also performed at each of the three cross-section

areas to determine the size and quality of streambed material. This was useful

in assessing substrate in relation to water quality and possible salmon spawning

areas.

Cross Section Surveys: Vegetation is often in the instrument’s line of sight.

Erosion rates estimations were attempted using a dendro-

geomorphological method of dating exposed tree roots at eroded sections of the

stream.  This is done using the major root axis as the relative position of the

former, original soil and relating that measurement to the age of the exposed

roots to determine the amount of soil erosion over time (Gartner 2007).  Using

Gartner (2007) guidelines, the only possible roots for analysis belonged to a

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small bay-laurel tree. However, due to very high moisture content within the

exposed roots, samples were very difficult to read and often fell apart shortly

after coring. However, this is a promising method of erosion rate analysis and is

worth attempting for other surveys in areas where sediment yield is crucial to

stream health.

Culverts: These culverts drain large areas of the watershed add significant amounts of sediment to the stream. They also create artificial pools and augment the size and depth of existing pools. The effects of the culverts could be mitigated by placing well-structured barriers to drain entrances to keep out sediment, leaf litter and other debris.

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Sediment yield: two photos of the same pool. The left photo was taken September 17 before rains came to the area. The right photo was taken October 30 after several storms. The increased turbidity of the water indicates a high level of sediment erosion from upstream and upslope sources. Increased turbidity and sediment in the stream decreases salmon habitat value.

Results

After conducting a detailed longitudinal profile, cross-section and pebble

count analysis of what we deemed the most suitable as well as heavily

impacted stretch of Larson Creek for trout and salmon spawning, we have

determined several restoration strategies that could be implemented to help

preserve and enhance the stream quality for Salmonids. The easiest and

least costly way to decrease the sediment loading into the scour pools

created by the two culverts in our study area would be to surround culvert

entrances with sediment blocking barriers, such as coconut fiber waddles.

Another option is to remove the culvert draining from the Lagunitas campus

and redirecting stream flow directly into San Geronimo Creek. This would

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decrease artificial pooling and sediment yield into Larsen Creek, which is

likely to have a higher salmon spawning density.

Streamflow rates could be reduced by strategically placing large

boulders, logs or root wads at the mouth of the culverts entering Larsen

creek. This would significantly slow the water flow and lead to decreased

erosion downstream

As for stream bank erosion, the planting of willow stakes and other

riparian vegetation structures will act as a stabilizing agent in the cut banks

as well as provide shade and predator protection for juvenile and spawning

Coho and Steelhead. Further investigation of upstream sediment sources

from hillside erosion could be remedied through native plantings and netting

on the springs and gullies that feed Larsen Creek. Larsen Creek’s location

right in the middle of an elementary school makes it a great place for getting

Marin’s youth educated and involved in the restoration and preservation of

these crucial breeding grounds for our native and endangered fish species.

With a little restoration and community involvement the quality of Larsen

Creek should be able to rebound and sustain its fruitful characteristics for

years to come.

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0 10 20 30 40 50 60 7075.800

76.000

76.200

76.400

76.600

76.800

77.000

77.200

77.400

77.600

77.800

Longitudinal Profile

Depth of River Bot -tom

Water Depth

Benchmark

Elev

ation

0 2 4 6 8 10 12 14 16 18 2076

76.577

77.578

78.579

79.580

80.581

Cross-Section 1

Horizontal Distance

Elev

ation

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0 2 4 6 8 10 12 14 16 18 2075

76

77

78

79

80

Cross-Section 2

Horizontal Distance

Elev

ation

0 1 2 3 4 5 6 7 8 9 1075

75.576

76.577

77.578

78.579

Cross-Section 3

Horizontal Distance

Elev

ation

(m)

9%

18%

38%

31%

4%

Cross Section 1 Pebble Count

2--8 Fine Gravel

8--16 Med Gravel

16--32 Coarse Gravel

32--64 Very Coarse Gravel

64--90 Small Cobble

Size (mm), Classification

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23%

22%

21%

22%

11%

1%

Cross Section 2 Pebble Count

<2 Sand

2--8 Fine Gravel

8--16 Med Gravel

16--32 Coarse Gravel

32--64 Very Coarse Gravel

64--90 Small Cobble

Size (mm), Classification

1%

9%

29%

43%

18%

1%

Cross Section 3 Pebble Count

<2 Sand

2--8 Fine Gravel

8--16 Med Gravel

16--32 Coarse Gravel

32--64 Very Coarse Gravel

64--90 Small Cobble

Size (mm), Classification

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References

Flosi, G., Downie. S., Hopelain, J., Bird, M., Coey, R., Collins, B. 1999. California Salmonid Stream Habitat Restoration Manual. CA Dept. of Fish and Game. 3rd Edition. 495 pages. Sacramento, CA.  Gartner, H. 2006.  Tree Roots – Methodological review and new development in dating and quantifying erosive processes.  Geomorphology (86) 2007: 243-251  Montgomery, D., and J. Buffington. 1993. Channel Classification, Prediction of Channel Response, and Assessment of Channel Condition. Washington State Timber, Fish & Wildlife Report TFW-SI-110-93-002. 110 pp. National Oceanic and Atmospheric Administration. 2008. Watershed Characterization: Lagunitas Creek Watershed. National Marine Fisheries Service.  Pincetich, C., T. Steiner, and P. Bouley. Coho and Steelhead Smolt Outmigration from the San Geronimo Valley, Marin County, 2009. Salmon Protection and Watershed Network.   Reese, H. and S. Philipps. 2005. Stream Inventory Report: Larsen Creek. Coastal Watershed Program. Rosgen, D.L., 1994.  A Classification of Natural Rivers. Catena, Vol 22: 169-199, Elsevier Science, B. V. Amsterdam.

SPAWN. 2004. County of Marin in Violation of CEQA: Ruling by Court of Appeals Requires CEQA Review for New House in Sensitive Creekside Habitat. Accessed from www.spawnusa.org

Steiner, Todd. SPAWN founder and father of Oscar. Personal communication over survey period.

 

 

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