Llano River and Sandy Creek Basins - Fluvial Geomorphic GIS Analyses

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Fluvial Geomorphic Analses of the Llano River and Sand Creek Basins, CentralTeas, Using Geographic Information Sstems (GIS) and Arc Hdro ToolsF T. HCE 394KD 9, 2005

R . T ( ) (- ).D . T

(3/) (Qb), . I (/), (), (% -), . M - . R , , . T , C T.

A E P L U T H C, L R S C (F 1), . T , (F 2). A, , C E P P L U. T

, . M, .

Figure 1. M .


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Figre 2. Annal peak eamflo (m3/) fo he Llano Rie a Llano, Tea and compaion ih ohe ie inimilal ied dainage bain.

Channel geome can be decibed in hee plane of adjmen: (1) planfom (efeed o a paen), (2) co-ecion (efeed o a hape), and (3) longidinal (efeed o a he pofile). Common indice ed o decibe channelpaen inclde cae (adi of cae (m)/channel idh (m)), meande aelengh (m), inoi (), anddegee of channel diiion fo a gien each (Fige 3). Channel hape i mo commonl deemined b he aio ofbankfll idh (m) o deph (m), he peence of ba o iland, and he mme of hee componen. The channelpofile i a plo of he bed eleaion along a each of inee. Thee plane of geomeic adjmen commonl hae beenindependenl eamined (e.g., Leopold and Maddock 1953; Leopold and Wolman 1957; Schmm 1963; Fegon 1987;Rogen 1994); hoee he hee plane eldom ae inegaed ih one anohe in die of mal adjmen (Fige4).


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Figre 3. Classification of channel pattern. Source: Church (1992), modified from Schumm (1985).

Figre 4. Model for mutual adjustment of channel slope, shape, and pattern of meandering rivers. Source: Rosgen

(1994).

An adequate understanding of mutual adjustment of channel geometry in the Llano River and Sandy Creek basinsshould be approached from a spatial context and organized in a spatial framework. A wide variety of fluvial geomorphic

parameters rely on spatial measurements, including, but not limited to, drainage area (km 2), channel width (m), sinuosity[channel length (m)/valley axis length (m)], radius of curvature (m), and slope (m/m). Clearly, the organization andanalysis of spatial data are integral to assessing fluvial geomorphic forms and processes. Currently, geographicinformation systems (GIS) not only serve as the most widely accepted platform for storage and organization of fluvialgeomorphic data, but are also useful for a variety of geomorphic analyses.

PURPOSE AND SCOPE

The purpose of this report is to present a variety of procedures and techniques used to store, organize, and analyze

fluvial geomorphic data associated with the Llano River and Sandy Creek basins in Central Texas. Specifically, sectionsbelow are devoted to: (1) the data and procedures necessary for stream and watershed delineation, (2) the creation oflongitudinal profiles, or plots of elevation with distance downstream, in the study area, and (3) an assessment of the

potential to model stream power (W/m2) in the study area.Much of the work completed for the project was performed in ESRI ArcGIS 9.1 using Arc Hydro Tools. Maidment

(2002) provides a synthesis of concepts, techniques, and guidelines associated with Arc Hydro Tools. Hydrography andelevation data used in the project were downloaded from the U.S. Geological Surveys National Hydrography Dataset(NHD) website (http://nhd.usgs.gov) and Seamless Data Distribution System (http://seamless.usgs.gov). No field datacollection efforts were necessary for completion of the project.

HYDROGRAPHY AND ELEVATION DATA

Hydrography data were downloaded from the U.S. Geological Survey National Hydrography Dataset (NHD)website (http://nhd.usgs.gov). High resolution (1:24,000) data were selected, and four subbasins were needed to coverthe Llano River and Sandy Creek basins (Figure 5). NHD data contain reach codes, feature names, and other codes touniquely identify river and stream reaches.


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Figre 5. High ei (1:24,000) Naia Hdgah Daae (NHD) bbai f La Rie ad Sad Ceebai.

Eeai daa ee daded f he U.S. Gegica Se Seae Daa Diibi Se ebie(h://eae.g.g). 30- ee ad 10-ee digia eeai de (DEM) (Fige 6) ee daded eca he La Rie ad Sad Cee bai. Ufae, he 10-ee DEM caied eica ie f daa, echig ac he eie d aea f h h. A ecd ae dad he 10-ee DEM a

ade, iedig he ae e. Jea Pache, Naia Maig Diii Lia f he USGS i Ai, a aachedab he -daa ie. A a e, he cec daa ee ided a eea had die f he USGS EahRece Obeai ad Sciece (EROS) Daa Cee. Recaga DEM aic ee ceaed f bh he 30- ad10- ee DEM ae ig he Rae Caca i Saia Aa f ESRI AcMa 9.1. The 30-ee DEM aic i11 0 egabe ad eied 2 idiida ae; he 10-ee DEM aic i 1 .81 gigabe ad eied 12 idiidaae.

Figre 6. 10-ee DEM aic aig he La Rie ad Sad Cee bai.

ARC HYDRO TOOLS

Ac Hd T (Maide 2002) i ESRI AcMa 9.1 ee ed geeae hdgic aia daae f hed aea. The daae geeaed b Ac Hd T ae ef f eaic deieai f ie ad eae ad aehed f DEM. Uie ideificai be, icdig HdID ad DaiID, ae gie ea eache ad aehed. Thee ae ef i aciaig hdgic daa f he each cae he aehedcae.

Pcede ieeed ig Ac Hd T f he La Rie ad Sad Cee bai ee: (1) fi i ihe a 30- ad 10-ee DEM aic, (2) cacae f dieci gid, (3) cacae f accai gid, (4)cacae ea defiii gid, ig a hehd f 100,000 ce (10 ae iee) f he 10-ee DEM, (5)

Norh Llano Rier

Soh Llano Rier

Llano Rier

Lake Bchanan anL.B.J.


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calclae eam egmenaion gid, (6) calclae cachmen gid, (7) poce dainage line, (8) poce adjoincachmen, (9) poce dainage poin, (10) delineae aehed a he ole of he Llano Rie, he Jame Rie,Beae Ceek, and Sand Ceek ing bach poin poceing, (11) geneae HdoEdge and HdoJncion daae ingHdo Neok Geneaion.

The dainage diide donloaded fom he NHD and delineaed fom he 30- and 10-mee DEM ing AcHdo Tool diffeed fom one anohe (Fige 7). The NHD bbain dainage diide i a genealied, hand-digiied line.The dainage diide poceed fo he 30- and 10-mee DEM end o follo one anohe, b can baniall deiaefom one anohe in paicla localiie. In one inance, a mall aea of he 10-mee delineaed aehed of he LlanoRie a miing (Fige 8). Thi aea a eplaced b ing he Diole command (ESRI AcToolbo 9.1) on hemiing baehed and added o he 10-mee aehed ih he Append command (ESRI Toolbo 9.1). Undeied

eice inide he appended ecion ee manall emoed ding an edi eion in ESRI AcMap 9.1.

Figre 7. Dainage diide fom he NHD and poceed fom 30- and 10-mee DEM ing Ac Hdo Tool. Thenoheaen edge of he Llano Rie bain epeen he mo eaggeaed deiaion of he hee daa oce.

Figre 8. Miing poion of he Llano Rie aehed ceaed fom he 10-mee DEM.

10-meer DEM30-meer DEM


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LONGITUDINAL PROFILES

L . T - . P , , (L L 1962; S S 1987; M W 1997). P . S

. C (N/2) (W/2).L , . I, ,

/.B C, L R,

ESRI AM 9.1. T - NHD . F, B C M ESRI AT 9.1. N, B C XT P , ://..(F 9). T C F P, - . FB C, 100 . U, : (1) OID , , (2) 100 (F 1 0). B , (F 11). T . M E 2003 . N,

10- DEM E V P ESRI AT 9.1. T . OID .F, B C (F 12). I DEM (F 13).

Figre 9. ESRI AM 9.1 XT P . T L R 100 .


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Figre 10. T ESRI AM 9.1 M T - 100 XT P . T 100 .

Figre 11. M B C. T OID 381 . A 381 390 100 . A OID 375, 71.82 .


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Figre 12. Beae Ceek geneall dipla a concae-p longidinal pofile, b lope emain emakabl conan

beeen 8 and 60 kilomee doneam. Sligh inceae in eleaion doneam ae aibed o boh he poimiof he eam channel o a eep alle all and he eolion of he DEM.

Figre 13. The poin highlighed in ble along Beae Ceek epeen a locaion hee eleaion inceae in adoneam diecion. Thi i eplained b he poimi of he channel o he eep alle all and he eolion of heDEM.

POTENTIAL FOR STREAM POWER MODELING

Seam poe (W/m2) i commonl ed o ae edimen anpo (Bagnold 1977; Caon and Giffih 1987)

and channel geome (Fegon 1987; an den Beg 1995) in ie em. Seam poe (W/m2) a inodced bBagnold (1966) o ae edimen anpo, and can be defined a:

= UgdS, hee


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(W/2), U (/),

(1000 /3),

g (9.80 /2), d (), S (/).

S (W/2) (N/2) (/).A GIS . F,

10- DEM U.S. C A E A . U

1 0- DEM L R S C , S S A ESRI AM 9.1 (F 1 4). N, Z S S A T NHD (F 15).

Figre 14. S S A ESRI AM 9.1. T Z S .


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Figre 15. Map of mean percent channel slope of the North Llano River, created in ESRI ArcMap 9.1 using the ZonalStatistics function and a 10-meter slope grid.

The other parameters needed to model stream power (W/m2) are flow velocity (m/s) and flow depth (m). Theseparameters can represent any given flow within the range of possible discharges of the river or stream. An initialapproach toward the application of these parameters to model stream power would be to choose a flow of interest, such a

bankfull discharge (m3/s). Field surveys of the channel reaches would also be necessary to characterize bankfull channeldepth (m). Assumptions of bankfull channel depth (m) may be empirically estimated from a plot of bankfull channel width(m) and depth (m). Finally, mean flow velocity (U) (m/s) could be estimated from a flow resistance equation, such as theDarcyWeisbach friction factor (f), defined as (Robert 2003):

f= 8gdS/U2, and 1/f= 2.11 + 2.03log10(d/ks), and

ks 6.8D50 , where

fis the dimensionless DarcyWeisbach friction factor, ksis the equivalent sand roughness height (m), and

D50is the median bed-particle size (m).

Again, field surveys would be necessary to make appropriate assumptions of bed- particle size (m) for channel reaches.Generally, a downstream decrease in bed-particle size (m) is observed, although tributaries and changes in lithology canreverse this trend.

CONCLUSIONS

An analysis of channel geometry in the Llano River and Sandy Creek basins requires hydrologic data, including

drainage areas (km2), discharges (m3/s), and channel slope. Arc Hydro Tools in ESRI ArcMap 9.1 is an excellent platformto generate and manage hydrologic data for fluvial geomorphic analyses. DEM processing in Arc Hydro Tools, combinedwith downloadable NHD data provide the best spatial hydrologic datasets for the study area. Edits to DEM-generatedwatersheds are common, but corrections are simple and do not compromise data quality. Using DEMs and NHD data,longitudinal profiles of elevation and distance downstream can be produced in ESRI ArcMap 9.1, although tedious manualtracking of downstream distance is involved. Finally, GIS has the potential to model stream power in river and streamreaches. Slope is the parameter that is most easily modeled. Velocity and flow depth parameters require fieldinvestigations, flow frequency assessments, and empirical assessments.

REFERENCES


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d / i / i h d 06/ /h i ll CE394K 0 h

Bagnold, R.A. 1966.An approach to the sediment transport from general physics. U.S. Geological Survey Professional

Paper 422I. Washington, DC: United States Government Printing Office.Bagnold, R.A. 1977. Bed load transport by natural rivers. Water Resources Research 13:303312.Carson, M.A., and Griffiths, G.A. 1987. Bedload transport in gravel channels.Journal of Hydrology (New Zealand) 26:1

151.Church, M. 1992. Channel morphology and typology. In The river handbookVolume 1, eds.P. Calow and G.E. Petts,

126143: Oxford, England, Blackwell.Ferguson, R.I. 1987. Hydraulic and sedimentary controls of channel pattern. In River channelsEnvironment and

process, ed. K.S. Richards, 129158. Oxford, England: Blackwell.Leopold, L.B., and Langbein, W.B. 1962. The concept of entropy in landscape evolution. U.S. Geological Survey

Professional Paper 500A. Washington, DC: United States Government Printing Office.

Leopold, L.B., and Maddock, T. 1953. The hydraulic geometry of stream channels and some physiographic implicationsU.S. Geological Survey Professional Paper 252. Washington, DC: United States Government Printing Office.

Leopold, L.B., and Wolman, M.G. 1957.River channel patternsBraided, meandering, and straight. U.S. Geological

Survey Professional Paper 282B:3985. Washington, DC: United States Government Printing Office.Maidment, D.L., ed. 2002.Arc HydroGIS for water resources. Redlands, CA: ESRI Press.Morris, P.H., and Williams, D.J. 1997. Exponential longitudinal profiles of streams.Earth Surface Processes and

Landforms 22:143163.Robert, A. 2003.River processes. London: Arnold.Rosgen, D.L. 1994. A classification of natural rivers. Catena 22:169199.Schumm, S.A. 1963. Sinuosity of alluvial rivers on the Great Plains. Geological Society of America Bulletin 74:1089

1100.Schumm, S.A. 1985. Patterns of alluvial rivers.Annual Review of Earth and Planetary Sciences 13:527.

Snow, R.S., and Slingerland, R.L. 1987. Mathematical modeling of graded river profiles. Journal of Geology 95:1533.van den Berg, J.H. 1995. Prediction of alluvial channel pattern of perennial rivers. Geomorphology 12:259279.

Llano River and Sandy Creek Basins - Fluvial Geomorphic GIS Analyses

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