sediment load from major rivers into puget sound and its ... · sediment-transport pathways ......
TRANSCRIPT
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.