Figure 1. Benefits and threats of river sediment to ecosystems and society.

Drainage Basins

Deltas and Marshes

Source of contaminants

Enables marsh accretion, buffers sea-level riseExcessive sediment buries habitatLack of sediment, inundation because of sea-level rise

BeachesForms beachesLack of sediment leads to erosion

MountainsSource of sedimentExtreme events deliver too much sediment

Provides nutrients and soil

Source of sediment

Forms berms (barriers) to floods

Buries vegetation

Offshore/Marine

Excessive sediment buries habitat, fragments ecosystemsCreates turbid water, loss of light for aquatic vegetation

Rivers

Flood Plains

Creates spawning habitat

Provides nutrients to benthic habitats

Changes in sediment size affect spawning habitat

Channel deposition increases flood risk

BenefitThreat

EXPLANATION

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

Fact Sheet 2011–3083August 2011

Sediment Load from Major Rivers into Puget Sound and its Adjacent WatersJonathan A. Czuba, Christopher S. Magirl, Christiana R. Czuba, Eric E. Grossman, Christopher A. Curran, Andrew S. Gendaszek, and Richard S. Dinicola

Printed on recycled paper

Highlights

• Eachyear,anestimatedloadof6.5milliontonsofsedi-mentistransportedbyriverstoPugetSoundanditsadjacentwaters—enoughtocoverafootballfieldtotheheightofsixSpaceNeedles.

• Thisestimatedloadishighlyuncertainbecausesedimentstudiesandavailablesediment-loaddataaresparseandhistoricallylimitedtospecificrivers,shorttimeframes,andanarrowrangeofhydrologicconditions.

• Thelargestsedimentloadsarecarriedbyriverswithglaci-atedvolcanoesintheirheadwaters.

• Researchsuggests70percentofthesedimentloaddeliveredtoPugetSoundisfromriversand30percentisfromshorelineerosion,butthemagnitudeofspecificcontributionsishighlyuncertain.

• Mostofariver’ssedimentloadoccursduringfloods.

Why is River Sediment Important to Puget Sound?

RiverscarryfreshwaterintoPugetSoundaswellassedimentandothermaterials,suchaswood,importanttoestuarineandnearshorehabitat,aquaticecology,andwaterquality.Historicalchannelizationofriversanddeltashasalteredsediment-transportpathwaysbyrestrictingsedimentdeliverytofloodplainsandredirectingsedimentoffshore.Paradoxically,sedimentisbothabenefitandathreattoecosystemsandsociety(fig. 1).Sufficient,butnotexcessive,amountsofsedimentareimportantresourcesforbeaches,deltas,andothercoastalhabitatsthatsustainecosystems,vegetation,andanimalsthatpeopledependon.Excessiveamountsofsedimentcanplacestressonavarietyofspeciesandhabitats.Forexample,eelgrassmeadows,whichprovideimportant

nearshoremarinehabitatforfish,shellfish,andinvertebrates,aswellasfoodforwaterfowlanddetritusfeeders,canbeburiedorfragmentedbyincreasedsedimentdeliveryassociatedwithriver-deltachannelization,likethoseoffshoreoftheSkagitRiver(Grossmanandothers,2011).Incontrast,whensedimentdeliveryisdepleted,nearshorecriticalhabitatandbeachescanbeerodedbynaturalcoastalprocessesandlost(Warrickandothers,2009).Changesinsedimentgrain-sizecompositionalsoaffectecosystems.Forexample,manyshellfishbedsandforage-fishspawningbeachesdependonaspecificsedimentgrain-sizecompositionthatislinkedtoland-useactivitiesandhydrologicconditionsthatreleaseandcarrysedimenttoPugetSound(Gelfenbaumandothers,2009).Waterquality,nearshoreandoffshorehabitats,andaquatic-ecosystemhealthareaffectedbycontaminantsandnutrientsthatpreferentiallyadsorbtofinesedimentsandaredeliveredtoPugetSound.Oncepresent,thesecontaminantscanbioaccumulateinfishandshellfishmakingtheseseafoodstoxicforhumanconsumption.

What is Sediment Load?

Ariver’ssedimentloadiscomputedfromwaterdischargeandsediment-concentrationdata,andrepresentsthefluxofsedimenttransportedbytheriver;itisusuallyexpressedasmasspertime,forexample,tonsperyear(tons/yr).Mostofariver’ssedimentloadoccursduringfloods.Sedimentiseithertransportedwithintheflowassuspendedloadortransportedalongtheriverbedbyrolling,sliding,orsaltating(hopping)asbedload.Asuspended-sedimentsampler,consistingofanozzleconnectedtoacontainerthatsamplesaflowingriver,isusedtomeasuretheconcentrationofsedimentinthewatercolumn.Similarly,abedloadsamplerplacedonthebottomofaflowingrivercollectsthecoarse-grainedsedimentmovingalongtheriverbed.Thesumofthemeasuredsuspendedloadandbedloadisthetotalload.Typically,bedloadrepresentsabout5–20percentofthetotalloadcarriedbyariver.MostreportedsedimentloadsforPugetSoundriversonlyincludethesuspendedloadandthusreflectaminimumestimateofthetotalsedimentload.

Figure 2. Mean annual discharge of major rivers draining into Puget Sound. The size of the arrow is scaled to the mean annual discharge. Data from Williams (1981).

124° 123° 122° 121°

49°

48°

47°

0 25 50 75 MILES

0 25 50 75 KILOMETERS

Strait of Georgia

Seattle

Tacoma

Bremerton

Olympia

Everett

Mt Vernon

Bellingham

Puget Sound

Mt. Baker

Glacier Peak

Mt. Rainier

Olympic Mountains

Casc

ade

Rang

e

Puget Lowland

British Columbia CANADA

Washington UNITED STATES

Strait of Georgia

Seattle

Tacoma

Bremerton

Olympia

Everett

Mt Vernon

Bellingham

British Columbia CANADA

Washington UNITED STATES

Puget Sound

Mt. Baker

Glacier Peak

Mt. Rainier

Olympic Mountains

Casc

ade

Rang

e

Puget Lowland

Salish Sea

PacificOcean

Strait of Juan de Fuca

DungenessRiver

ElwhaRiver

Hamma Hamma RiverDuckabush River

Dosewallips River

Big Quilcene River

Deschutes River

Nooksa

ck Rive

r

Nooksa

ck Rive

r

Samish RiverSamish River

Skagit RiverSkagit River

Stillaguamish RiverStillaguamish River

Snohomish RiverSnohomish River

Lake WashingtonShip CanalLake WashingtonShip Canal

Duwamish River

Duwamish RiverPuyallup River

Puyallup RiverNisqually River

Nisqually River

Deschutes River

All other

tribu

taries

All other

tribu

taries

Skokomish RiverSkokomish River

Hamma Hamma RiverDuckabush River

Dosewallips River

Big Quilcene River

DungenessRiver

ElwhaRiver

Fraser River

3,200

3,600

190

2,700

1,400

400 2,100

570670

180

4602,000

500

1,3001,400

3,130

3,200

18,000

10,000

3,600

190

2,700

1,400

400 2,100

570670

180

4602,000

500

1,3001,400

3,100

EXPLANATIONDrainage-basin boundary

Subbasin boundary

Mean annual discharge, in cubic feet per second

190

Factors Affecting Sediment Delivery to Puget SoundAnumberofgeologicandgeomorphicfactorsaffect

sedimentsupplytoPugetSound.Watershedgeology,slope,landuse,precipitation,mountainupliftrates,volcanism,glaciers,lahars,andweatheringallaffectthesedimentloadcarriedbytheregion’srivers.Riversdrainingglaciatedterrainarenotoriouslyladenwithlargeamountsofsediment.Landuse,includingagricultural,forested,andurbanareas,affectsthesedimentload,aswellasnutrientsandtoxics,carriedbyrivers.DamswithinabasinstoresedimentthatultimatelyreducessedimentdeliverytoPugetSoundanditsadjacentwaters.However,removaloflargedams,likeintheplannedElwhaRiverdam-removalprojectbeginningin2011,canresultinlarge,short-termreleasesofsedimentdownstreamandanewlyadjustedannualsedimentloadinthelongterm.

Climatechangeandshiftinglandusethreatentoaltersedimentloadsinrivers.Anincreasedsedimentloadmaybeimportantinmaintainingestuarineandnearshorehabitatsassealevelrisesinresponsetoclimatechangebyenablingmarshesandcoastlinestoaccumulatesedimentandbuildtopography.ClimatepatternshiftsalsowillalterthetimingandmagnitudeoffloodsthatcarrysedimenttoPugetSound.

Sediment Transported by Rivers into Puget SoundEachyear,about12trilliongallons(totalmeanannual

dischargeofabout52,000cubicfeetpersecond[ft3/s])offreshwaterflowintoPugetSoundanditsadjacentwatersfromtheregion’sriversandstreams(fig. 2,table 1).Theserivers,

inturn,carryanestimated6.5milliontons(1ton=2,000pounds)ofsedimentintoPugetSoundanditsadjacentwaters(fig. 3,table 1).Thissedimentisderivedfromtheweatheringanderosionofbedrockandsoilinbasinswhererunofffromrainandsnowcarriesparticlesintomain-stemriversthattransportthematerialdownstreamtoPugetSound.Thequantityandsizeofsedimentmovedbyriversdependsondischargeandriverslope,andalthoughevensmallstreamscarrysiltsandclays,onlythesteepestriverstransportgravels,cobbles,andboulders.Mountainousriversreadilytransportgravelsandcobbles,anddepositthissedimentdirectlyintoPugetSoundwheretheseriversdraindirectlyintotheSound,suchastheElwhaandDungenessRivers.AsmountainousriversenterPugetLowland,thecoarseparticles(gravel,cobbles,andboulders)tendtodepositonriverbeds,suchasinthePuyallupRiver.Thiscoarse-sedimentdepositionreducestheriver’scapacitytoconveyafloodwithoutovertoppingitsbanksandincreasesthefloodhazard,necessitatingrivermanagementtoreducefloodrisktonearbypeopleandinfrastructure(Czubaandothers,2010).Fineparticles(clay,silt,andsand),however,continuetobecarrieddownstream,outofthePugetLowland,andintoPugetSound.SedimentdeliveredintoPugetSoundisredistributedbycomplexinteractionsoftidalandwind-drivencurrentsthroughoutthebaysandinlets.

Available Sediment-Load StudiesOnlyahandfulofwater-qualityandsediment-transport

studieshavebeenconductedtoquantifysedimentloadingfromriversintoPugetSound,andthemajorityofthesestudieswerelimitedtospecificriversusingsedimentdatacollectedduringonlyafewyearsinthe1960sand1970s(table 1).Insomecases,thesediment-loadestimateswerebasedonlimitedmeasurementsaddingsignificantuncertaintybecausesedimentloadinariverisvariable,changingbyasmuchasanorderofmagnitudebetweenyearsorbetweenstorms(forexample,Nelson,1979).Inaddition,themeasurementsmaynothave

Modern Sediment-Surrogate Monitoring Technologies

Recentadvancesinhydroacousticandopticaltechnologieshavefosteredrenewedinterestinmonitoringandtrackingsedimentloadsinrivers(GrayandGartner,2009).Couplingthesetechnologieswithstrategicsedimentsamplingenablesthenear-continuousmeasurementandreportingofsedimentloadinriversatafractionofthecostoftraditionalsediment-measurementtechniquesappliedduringthe20thcentury.Inadditiontoreportingthesedimentloadinagivenriver,theseinstrumentsalsohavethecapabilitytoestimateparticle-sizedistributionofsedimentdeliveredbyrivers.

Figure 3. Annual sediment load of major rivers draining into Puget Sound measured at or near the river mouth. The size of the arrow is scaled to the annual sediment load. Data sources listed in table 1.

124° 121°

49°

47°

0 25 50 75 MILES

0 25 50 75 KILOMETERS

Strait of Georgia

Seattle

Tacoma

Bremerton

Olympia

Everett

Mt Vernon

Bellingham

Puget Sound

Mt. Baker

Glacier Peak

Mt. Rainier

Olympic Mountains

Casc

ade

Rang

e

Puget Lowland

British Columbia CANADA

Washington UNITED STATES

Strait of Georgia

Seattle

Tacoma

Bremerton

Olympia

Everett

Mt Vernon

Bellingham

British Columbia CANADA

Washington UNITED STATES

Puget Sound

Mt. Baker

Glacier Peak

Mt. Rainier

Olympic Mountains

Casc

ade

Rang

e

Puget Lowland

Salish Sea

PacificOcean

Strait of Juan de Fuca

DungenessRiver

ElwhaRiver

Hamma Hamma RiverDuckabush River

Dosewallips River

Big Quilcene River

Deschutes River

Nooksa

ck Rive

r

Nooksa

ck Rive

r

Samish RiverSamish River

Skagit RiverSkagit River

Stillaguamish RiverStillaguamish River

Snohomish RiverSnohomish River

Lake WashingtonShip CanalLake WashingtonShip Canal

Duwamish River

Duwamish RiverPuyallup River

Puyallup River

Nisqually River

Nisqually River

Deschutes River

All other

tribu

taries

All other

tribu

taries

Skokomish RiverSkokomish River

Hamma Hamma RiverDuckabush River

Dosewallips River

Big Quilcene River

DungenessRiver

ElwhaRiver

Fraser River

??

1211

30

6

12035

1,400

2,800

1818

3.33.3

120

?? 980

490

??

35

410

1211

30

6

??

210210

EXPLANATIONDrainage-basin boundarySubbasin boundaryAnnual sediment load, in thousands of tonsPublished load estimates could not be found or do not exist

3.3

123° 122°

48°

?

includedanaccuraterepresentationoffloodswhenthegreatestsedimentconcentrationsoccur,whichwouldleadtounderestimatesoftheannualsedimentload.Thesediment-loadestimates(table 1)wereobtainedfromreadilyavailablestudiesbyfederalandstateagencies,consultants,andacademicresearchers.Onlythosestudieswheretotal-orsuspended-loadestimatesweredeterminednearthemouthoftherespectiveriverasitenteredPugetSoundwereincludedintable 1andfigure 3.Thesesediment-loadestimateswereconvertedintotonsperyearasnecessaryandwereaveragedtogetherwhenmultiplestudiesprovideddifferentestimates.Themostreliablesediment-loadestimatesincludedsedimentdataspanningmanyyears(forexample,theloadestimatesfromtheSkagitandDeschutesRivers;table 1).TheDeschutesRiversediment-loadestimateisuniquebecauseitisbasedonrepeatsurveysofthedeltavolumeinadditiontodirectmeasurementsofsedimentloadintheriver.Allothersediment-loadestimatesfromriversdrainingtoPugetSoundwereofsuspendedloadonlyanddonotaccountforbedload.Theestimatesbasedondatacollectedforafewyearsmayormaynotrepresenttheriver’slong-termaveragesedimentload.

Sediment-Load Estimates for Puget Sound Rivers

Thelargestsedimentloadsarenotnecessarilythosecarriedbytherivershavingthelargestmeanannualdischarge.Instead,thethreeriverscarryingthelargestsedimentloads,theSkagit,Nooksack,andPuyallupRivers,allcontainglaciatedvolcanoesintheirheadwaters(fig. 3).TheSkagitRiverdrainsbothMountBakerandGlacierPeak,althoughmuchofthesedimentloadderivedfromMountBakerisretainedinmanmadereservoirs.TheNooksackRiverdrainsthenorthernsectionsofMountBakerandthePuyallupRiverdrainsthenorthernandwesternsectionsofMountRainier.

TheothermajorsourceofsedimenttoPugetSoundisfromshorelineerosion,whichcontributessedimentofallgrainsizes,includingclay,silt,sand,gravel,cobbles,andboulders,toareasawayfromriverdeltas.Dexterandothers(1981)estimatedshorelineerosioncontributesabout2.6milliontonsofsedimentperyeartoPugetSound;however,theuncertaintyinthisestimateislarge.Thecombinedsedimentloadfromriversandshorelineerosionisabout9.1milliontonsperyear,about70percentisfromriversand30percentisfromshorelineerosion.

WhilenotdrainingdirectlyintoPugetSound,theFraserRiverinBritishColumbiadrainsintotheStraitofGeorgiaandisaprodigiouscontributoroffreshwaterandsedimentintothegreaterSalishSea(table 1).TheFraserRivercarriesatotalloadofabout20milliontonsofsedimentperyearintotheStraitofGeorgia(ChurchandKrishnappan,1998).

Opportunities for Monitoring and Basic ResearchThesediment-loadestimatesforriversdrainingtoPuget

Soundmaybeinaccuratebyanorderofmagnitude(table 1)

becauseofthesparseavailabilityofreliablesedimentdataandthevariablenatureofsedimenttransport.Theproblemisfurtherexacerbatedbytheout-of-datestatusofmanydatasetsassignificantchangesinlanduse,urbanization,andclimateinthe21stcenturylikelyhavemodifiedsedimentsourcesandtransportsincethe1970s,whenmostoftheregion’ssedimentdatawerecollected.Recentstrategicsamplingofsedimentduringtheentirerangeoflow-andhigh-flowconditions,aswellasdifferentseasons,hasgreatlyimprovedtheabilitytoquantifyandreduceuncertaintyofsediment-deliveryestimatesbytheSkagitRiver(Curranandothers,2011).Giventheimportantaffectofsediment,asabenefitandathreat,toPugetSoundecosystems,detailedmonitoringandanalyticalunderstandingofsedimentload,size,quality,andmovementareneededtobestunderstand,protect,andrestoreimportantecosystemprocessesandfunctionsinPugetSound.

For more information contact:

Director, Washington Water Science CenterU.S. Geological Survey, 934 Broadway, Suite 300Tacoma, Washington 98402http://wa.water.usgs.gov

References Cited

CapitolLakeAdaptiveManagementPlan1999to2001,1999:ThurstonRegionalPlanningCouncil,103p.

Church,M.,andKrishnappan,B.G.,1998,Sedimentsources,transportprocesses,andmodelingapproachesfortheFraserRiverinC.GrayandT.Tuominen,eds.,HealthoftheFraserRiverAquaticEcosystem:EnvironmentCanada,DOEFRAP1998–11,18p.

Curran,C.A.,Grossman,E.E.,Mastin,M.C.,andHuffman,R.L.,(inpress),SedimentloadanddistributioninthelowerSkagitRiver,SkagitCounty,Washington,USA.ForsubmissiontoContinentalShelfResearch.

Czuba,J.A.,Czuba,C.R.,Magirl,C.S.,andVoss,F.D.,2010,Channel-conveyancecapacity,channelchange,andsedimenttransportinthelowerPuyallup,White,andCarbonRivers,westernWashington:U.S.GeologicalSurveyScientificInvestigationsReport2010–5240,104p.

Dexter,R.N.,Anderson,D.E.,Quinlan,E.A.,Goldstein,L.S.,Strickland,R.M.,Pavlou,S.P.,Clayton,J.R.,Kocan,R.M.,andLandolt,M.,1981,AsummaryofknowledgeofPugetSoundrelatedtochemicalcontaminants:NationalOceanicandAtmosphericAdministrationTechnicalMemorandumOMPA-13,435p.

Downing,J.,1983,ThecoastofPugetSound:itsprocessesanddevelopment.UniversityofWashingtonPress,Seattle,Wash.,126p.

Embrey,S.S.,andFrans,L.M.,2003,Surface-waterqualityoftheSkokomish,Nooksack,andGreen-DuwamishRiversandThorntonCreek,PugetSoundbasin,Washington,1995–98:U.S.GeologicalSurveyWater-ResourcesInvestigationsReport02–4190,192p.

Gelfenbaum,G.,Fuentes,T.L.,Duda,J.J.,Grossman,E.E.,andTakesue,R.K.,eds.,2009,ExtendedabstractsfromtheCoastalHabitatsinPugetSound(CHIPS)2006Workshop,PortTownsend,Washington,November14–16,2006:U.S.GeologicalSurveyOpen-FileReport2009–1218,136p.

Gray,J.R.,andGartner,J.W.,2009,Technologicaladvancesinsuspended-sedimentsurrogatemonitoring:WaterResourcesResearch,v.45,20p.

Grossman,E.E.,George,D.A.,andLam,A.,2011,ShallowstratigraphyoftheSkagitRiverDelta,Washington,USAderivedfromsedimentcores:U.S.GeologicalSurveyOpen-FileReport2011–1194.

Nelson,L.M.,1971,SedimenttransportbystreamsintheSnohomishRiverbasins,Washington:October1967–June1969:U.S.GeologicalSurveyOpen-FileReport71–215,96p.

Nelson,L.M.,1974,SedimenttransportbystreamsintheDeschutesandNisquallyRiverbasins,Washington:November1971–June1973:U.S.GeologicalSurveyOpen-FileReport74–1078,33p.

Nelson,L.M.,1979,SedimenttransportbytheWhiteRiverintoMudMountainReservoir,Washington,June1974–June1976:USGSWater-ResourcesInvestigationsReport78–133,26p.

Paulson,A.J.,Feely,R.A.,CurlJr.,H.C.,Crecelius,E.A.,andRomberg,G.P.,1988,SourcesandsinksofPb,Cu,Zn,andMninthemainbasinofPugetSound:NationalOceanicandAtmosphericAdministrationTechnicalMemorandumERLPMEL-77,26p.

Santos,J.F.,andStoner,J.D.,1972,Physical,chemical,andbiologicalaspectsoftheDuwamishRiverEstuaryKingCounty,Washington1963–67:U.S.GeologicalSurveyWater-SupplyPaper1873–C.,74p.

Warrick,J.A.,George,D.A.,Gelfenbaum,G.,Ruggiero,P.,Kaminsky,G.M.,andBeirne,M.,2009,Beachmorphologyandchangealongthemixedgrain-sizedeltaofthedammedElwhaRiver,Washington:Geomorphology,v.111,p.136–148.

Williams,J.R.,1981,Principalsurface-waterinflowtoPugetSound,Washington:U.S.GeologicalSurveyWater-ResourcesInvestigationsReport84–4090,6sheets.

Wise,D.R.,RinellaIII,F.A.,Rinella,J.F.,Fuhrer,G.J.,Embrey,S.S.,Clark,G.E.,Schwarz,G.E.,andSobieszczyk,S.,2007,Nutrientandsuspended-sedimenttransportandtrendsintheColumbiaRiverandPugetSoundbasins,1993–2003:U.S.GeologicalSurveyScientificInvestigationsReport2007–5186,117p.

Table 1. Puget Sound sediment-load data.

[MeanannualdischargedatafromWilliams(1981).mi2,squaremile;ft3/s,cubicfeetpersecond;tons/yr,tonsperyear;Annualsedimentload:n.e.,publishedloadestimatescouldnotbefoundordonotexist;--,nodata]

Basin (area mi2)

Mea

n an

nual

di

scha

rge

(ft3 /s

)

Ann

ual s

edi-

men

t loa

d (to

ns/y

r)

Tim

e pe

riod

w

hen

sed-

imen

t-lo

ad

data

wer

e co

llect

ed

Skagit(3,200)1 18,000 2,800,000 1974–93,2006–09

Snohomish(1,800)2,3,4 10,000 490,000 1964–66,1967–68,2000

Puyallup(980)2,4 3,600 980,000 1964–66,2000Nooksack(840)2,4,5 3,200 1,400,000 1964–66,

1996–98,2000Nisqually(770)2,6 2,100 120,000 1964–66,

1971–72Stillaguamish(700)2 2,700 18,000 1964–66LakeWashingtonShipCanal(600)7

1,400 3,300 1981–82

Duwamish(500)4,5,8 1,400 210,000 1964–66,1996–98,2000

Elwha(320) 2,000 n.e. --Skokomish(250)2,4,5 1,300 410,000 1964–66,

1996–98,2000Dungeness(200) 460 n.e.Deschutes(170)9 400 35,000 1952–98Samish(120) 190 n.e. --Dosewallips(120)2 670 30,000 1964–66HammaHamma(80)2 500 12,000 1964–66Duckabush(80)2,4 570 11,000 1964–66,2000BigQuilcene(70)2 180 6,000 1964–66Allothertributaries(2,300) 3,100 n.e. --TotalPugetSound(13,000) 52,000 6,500,000 --Fraser(85,000)10 130,000 20,000,000 1965–96

1Curranandothers,2011. 6Nelson,1974.2Downing,1983. 7Paulsonandothers,1988.3Nelson,1971. 8SantosandStoner,1972.4Wiseandothers,2007. 9CapitolLakeAdaptiveManagementPlan,1999.5EmbreyandFrans,2003. 10ChurchandKrishnappan,1998.