U.S. Department of the InteriorU.S. Geological Survey

Fact Sheet 2014–3038April 2014

Estimating Suspended Sediment in Rivers Using Acoustic Doppler Meters

Printed on recycled paper

Prepared in cooperation with the Federal Interagency Sedimentation Project

Key Points

• TheU.S.EnvironmentalProtectionAgency(2009)estimatesthatexcessivesedimentistheleadingcauseofwater-qualityimpairmentinwaterbodiesintheUnitedStates.Thecostofdamagesattributabletosedimentishigh,estimatedatmorethan$20billionannually(Osterkampandothers,2004).

• Sedimentmonitoringisessentialtoinformedsolutionstosediment-relatedissues.However,sedimentmonitoringbytheU.S.GeologicalSurvey(USGS)hasdecreasedconsiderablyoverthepastquartercentury.

• Newtechniquesthatmakeuseofacousticbackscatterhaveshowngreatpotentialforaccuratelyandcost-effectivelyestimatingsuspended-sedimentconcentrations.

Monitoring sediment is important for the management of water resources. “Sediment monitoring data can be used to determine effectiveness of sediment reduction actions in the watershed and guide adaptive sediment management,” states Richard Turner of the U.S. Army Corps of Engineers, Walla Walla District. “Monitoring data helps foster fact-based working relationships with regulators and stakeholders, and contributes to the U.S. Army Corps of Engineers’ public safety efforts and flood risk reduction.”

Figure 1. High sediment concentrations can reduce biological productivity of aquatic systems (A), impair water quality (B), (C), (E), decrease flood-protection capacity of levees and dams (D), decrease reservoir storage capacity (D) and affect waterway navigation (E).

Why Is Sediment Important to Measure?Sedimentcanbetransportedassuspendedload

(moveswiththeflowoftheriver)orasbedload(rollsalongtheriverbed)orcanbedepositedontheriverbedorbank.TheconceptsdescribedinthisFactSheetfocusonmethodsforestimatingsuspendedsedimentbecauseitistypicallythelargestpartoftotalsedimenttransportedinariver(Meadeandothers,1990).Sedimentisnaturallyoccurringandessentialtosupportingtheecologicalfunctionofawaterbody.Highsedimentconcentrationsinriversandstreams,however,canbedetrimental(fig.1).

How Is Suspended Sediment Measured?

Formanyyears,USGSscientistshavecollectedsedimentsamplesfrommultipleverticalsectionsinriversusingpointordepth-integratingsamplers.Sedimentsamplesrepresentthesedimentconcentrationinaparticularriveratagivenpointintime.Tocontinuouslyestimatesedimentconcentrationsduringperiodswhensamplesarenotcollected,scientistsdeveloprelationsbetweensedimentconcentrationsandotherparameters,mostcommonly,streamflowmeasuredatanearbystreamgage.

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However,thisapproachoftendoesnotaccuratelyestimatesedimentconcentrations.Sedimentconcentrationsmaydifferforthesamestreamflows,particularlyontherisingandfallinglimbofthestreamflowhydrographduringastormevent(fig.2).

Why Are Surrogate Technologies Useful for Estimating Suspended Sediment?

Sedimentsurrogatetechnologiesoftencanreliablyestimatesedimentconcentrationandtypicallyareeasier,safer,and(or)lessexpensivetoutilizethantraditionalsedimentdatacollectionmethods.TheuseofacousticDopplermeters(fig.3),inparticular,showsgreatpotentialforestimatingsedimentbecausethey:• Arealreadyextensivelyusedinstreamflowmonitoringandprovideconcurrentrivervelocitydata;

• Provideamoredirectmeasureofsedimentconcentrationsthantheuseofstreamflow(fig.2);

• Arenotassusceptibletobiofoulingasothersurrogatetechnologies,suchasturbiditysensors;

• Measurealargersamplingvolumethanothersurrogatetechnologies;and

• Canpotentiallyprovideinformationonsedimentsizeifmultipleacousticfrequenciesareused.Surrogatetechnologiesallowcontinuousestimatesof

sedimentconcentrationandload,whichcanbemadeavailablereal-timethroughtheUSGSNationalWaterInformationSystem(U.S.GeologicalSurvey,2014).Real-time,continuoussediment

datacanbeusefulformonitoringriverresponsedownstreamofareasaffectedbyrecentwildfires,constructionorremediationactivities,leveefailures,orchanginglanduses.Additionally,real-timedatacanprovideanearlywarningforoperatorsofmunicipalwatersupplyandhydropowerfacilitiesconcernedwithavoidingdamagetoinfrastructurefromsediment.

How Does a Sediment Acoustic Surrogate Streamgage Work?

ScientistsdeployanacousticDopplermetertypicallyatafixedlocationinariver.Themetertransmitspulsesofsoundataknownfrequency,alongtwoormorebeamsangledtoflow,whichreflectoffsedimentinthewater(fig.4).AcousticDopplermetersareprimarilyusedtomeasurewatervelocityusingtheDopplerprinciplebutalsooutputareturnpulsestrengthindicator,called“backscatter”(LevesqueandOberg,2012).Althoughbackscatterismostoftenusedtoassurethequalityofvelocitydata,italsocanserveasanindicatoroftheconcentrationofsedimentinthemeter’smeasurementvolume.

ScientistscollectsedimentsamplesfromtheriverwhiletheacousticDopplermeterisdeployed(fig.4)andrelatethesedimentconcentrationstobackscattermeasurements.Themeasuredbackscatterdataarecorrectedforlossesresultingfromspreadingoftheacousticbeamsandabsorptionofthepulsebywaterandsediment.Aftersamplesarecollectedoverarangeofhydrologicandsedimentconditions,scientistsdeveloparelationbetweenthesedimentconcentrationsandcorrectedbackscatterdata(fig.5)thatisusedtocontinuouslyestimatesedimentconcentrations.ResearchisongoingtoevaluatetheperformanceandoperationallimitsofacousticDopplermetersasasurrogateforsediment,particularlyduringperiodsofchangingsedimentgrain-sizedistribution.

Figure 2. Suspended-sediment concentrations and streamflow during a storm event on Kickapoo Creek near Bloomington, Illinois (USGS streamgage 05579630). Sampled sediment concentrations peak prior to the peak in streamflow and are not equal at identical streamflows during the event. Sediment concentrations estimated using data from an acoustic Doppler meter at the streamgage closely match sampled concentrations.

Figure 3. Acoustic Doppler meters used for estimating suspended-sediment concentrations in the Clearwater River at Spalding, Idaho (USGS streamgage 13342500).

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EXPLANATION

Sediment Acoustic Surrogate Monitoring in the United States

TheUSGScollectssuspended-sedimentsamplesatabout673streamgagesintheUnitedStates(asof2012).Suspended-sedimentsamplesandacousticDopplermeterdataareconcurrentlycollectedat115streamgagesin22States,andrelationshavebeencompletedorarebeingdevelopedat51ofthesestreamgagestoestimatesedimentconcentrations(fig.6).Asof2012,theUSGShasdeployedacousticDopplermetersinfixedlocationsat470streamgagesintheUnitedStatesforthepurposeofmonitoringstreamflow.Collectingsedimentsamplesanddevelopingsurrogaterelationsatthesestreamgageswouldgreatlyenhanceanational,continuoussedimentmonitoringnetwork.

Want to Learn More?TheFederalInteragencySedimentationProject(FISP)

conductsandsponsorsresearchonemergingtechnologiesforsedimentmonitoring,includingtheuseofacousticDopplermeters.Additionally,theUSGShascreatedaSedimentAcousticLeadershipTeam(SALT)tohelpguidethedirectionofsedimentacousticresearchintheUnitedStates.LearnmoreaboutFISPathttp://water.usgs.gov/fisp/andSALTathttp://water.usgs.gov/osw/SALT/

Figure 4. Example of a sediment acoustic surrogate streamgage (adapted from image provided by SonTekTM - A Xylem Brand.)

USGS Sediment sampling vessel

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Relation between streamflow and

Relation between acoustic backscatter and suspended-sediment concentration, 2008–2010:

R² (Coefficient of Determination) = 0.93

suspended-sediment concentration, 2008–2010: R² (Coefficient of Determination) = 0.55

Samples, streamflow relationSamples, acoustic relation

EXPLANATION

Figure 5. Relations developed between suspended-sediment concentration and streamflow, and backscatter measurements from an acoustic Doppler meter in the Clearwater River at Spalding, Idaho (USGS streamgage 13342500). The relation developed using an acoustic Doppler meter is better than the relation developed using streamflow, partially because streamflow at the streamgage comes from a combination of regulated (dammed) and unregulated (free-flowing) sources, which have varying sediment contributions.

Publishing support provided by the U.S. Geological SurveyTacoma Publishing Service Center Graphic design: Bill Gibbs

Wood, M.S., 2014, Estimating suspended sediment in rivers using acoustic Doppler meters: U.S. Geological Survey Fact Sheet 2014-3038, 4 p., http://dx.doi.org/10.3133/fs20143038.

Author: Molly S. Wood, Hydraulic Engineer U.S. Geological Survey Idaho Water Science Center mswood@usgs.gov

For additional information, contact:,,

U.S. Geological Survey Office of Surface Water 415 National Center, 12201 Sunrise Valley Drive Reston, Va. 20192 http://water.usgs.gov/osw/contact.html

References Cited

Levesque,V.A.,andOberg,K.A.,2012,Computingdischargeusingtheindexvelocitymethod:U.S.GeologicalSurveyTechniquesandMethods,book3,chap.A23,148p.,http://pubs.usgs.gov/tm/3a23/).

Meade,R.H.,Yuzyk,T.R.,andDay,T.J.,1990,MovementandstorageofsedimentinriversoftheUnitedStatesandCanada,inWolman,M.G.,andRiggs,H.C.,eds.,Surfacewaterhydrology—ThegeologyofNorthAmerica:Boulder,Colo.,GeologicalSocietyofAmerica,p.255–280.

Osterkamp,W.R.,Heilman,Phil,andGray,J.R.,2004,AninvitationtoparticipateinaNorthAmericansediment-monitoringnetwork:Eos,TransactionsAmericanGeophysicalUnion,v.85,no.40,p.386–388.

U.S.EnvironmentalProtectionAgency,2009,Nationalwaterqualityinventory—ReporttoCongress,2004reportingcycle,January2009:OfficeofWater,Washington,D.C.,EPA841-R-08-001,43p.

U.S.GeologicalSurvey,2014,NationalWaterInformationSystem(NWISWeb):U.S.GeologicalSurveydatabase,accessedFebruary6,2014,athttp://waterdata.usgs.gov/nwis/.

Sediment Acoustic Surrogate Studies of Interest

Gray,J.R.,andLanders,M.N.,2014,Measuringsuspendedsediment,inAhuja,S.,ed.,ComprehensiveWaterQualityandPurification:Elsevier,Waltham,v.1,p.157–204.

Landers,M.N.,2012,Fluvialsuspendedsedimentcharacteristicsbyhigh-resolution,surrogatemetricsofturbidity,laser-diffraction,acousticbackscatter,andacousticattenuation:GeorgiaInstituteofTechnology,SchoolofCivilandEnvironmentalEngineering,Atlanta,Georgia,Ph.D.dissertation,236p.,accessedFebruary6,2014,athttp://hdl.handle.net/1853/43747.

Topping,D.,Wright,S.A.,Melis,T.S.,andRubin,D.M.,2006,High-resolutionmonitoringofsuspended-sedimentconcentrationandgrainsizeintheColoradoRiverusinglaser-diffractioninstrumentsandathree-frequencyacousticsystem—Proceedingsofthe8thFederalInteragencySedimentationConference,April2–6,2006:Reno,Nevada,CD-ROM,ISBN0-9779007-1-1.

Wood,M.S.,andTeasdale,G.N.,2013,UseofsurrogatetechnologiestoestimatesuspendedsedimentintheClearwaterRiver,Idaho,andSnakeRiver,Washington,2008–10:U.S.GeologicalSurveyScientificInvestigationsReport2013-5052,30p.,http://pubs.usgs.gov/sir/2013/5052/.

Acknowledgments

TheauthorwishestothankMarkLanders,CaseyLee,TimStraub,KevinOberg,andCoryWilliams(U.S.GeologicalSurvey)andTimCalappiandRichardTurner(U.S.ArmyCorpsofEngineers)forcontributinginformationtothispublication.

Photographs taken by: Figure 1E, Tom Roorda (www.RoordaAerial.com); Figure 1C, U.S. Army Corps of Engineers–Detroit; Figure 1D, Bureau of Reclamation; All other photographs taken by U.S. Geological Survey employees.

ISSN 2327-6916 (print)ISSN 2327-6932 (online)http://dx.doi.org/10.3133/fs20140328

Figure 6. Number and locations of streamgages in the United States where suspended-sediment and acoustic Doppler meter data are collected by the U.S. Geological Survey (as of 2012).

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EXPLANATION

Sediment acoustic surrogate streamgages with relations completed or in development to estimate suspended-sediment concentration

Number of streamgages per State where suspended- sediment and acoustic data are collected

01-2 3-4 5-67 or more

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