Habitat ScalesOver what range of scales does LWD influence channels?Wood in riversExtent of global forestsMuch of our understanding of river systems was developed in areas that either lacked large wood or that had been cleared of woArmy Corps of Engineers aggressively “de-snagged” American RiversChannel Unit Scale Reach ScaleValley Segment ScaleLog jams can influence even large riversPosition in Channel NetworkWatershed ScaleEffects of Wood in RiversHow big does a log have to be in order to influence a river? ELJs: Engineered Log JamsFloodplain setbacksUvas Creek, January 1996River RestorationRiver Engineering: Flood Control…River Restoration: Habitat ImprovementclimateTime-constant variablesgeologychannel gradientvalley formhydrological regimesediment inputsriparian vegetationTime-variable driverscatchment vegetationchannel engineeringGeologyClimateRegional VegetationLand UsePollutionRiver EngineeringFloodplain DevelopmentRestoration/LWDFlow RegimeSediment RegimeWood RegimeHabitatStructure &DynamicsBiotic Condition(Salmon Viability)Habitat ScalesThe supply and transport of water, sediment, and wood interact to structure salmon habitat.Over what range of scales does LWD influence channels?Geomorphic Province WatershedValley SegmentChannel ReachPoolPoolBarBarRiffleChannelmorphologyBankmaterialFlowobstructionsValleyslopeConfinementSediment Water WoodRiparianvegetationRiver RestorationRiver RestorationApplication of general principles to the context Application of general principles to the context of a particular site.of a particular site.1.1.Assessment / diagnosisAssessment / diagnosis2.2.DesignDesign3.3.ImplementationImplementation4.4.MonitoringMonitoring10 Commandments of River RestorationI. Do no harmII. Look beyond the channel to assess it in contextIII. Use native materialsIV. Emulate natural analogsV. Let the channel do the workVI. Let the channel use its floodplainVII. Manage inputs to the system so that the river can fix itselfVIII.Use direct manipulation of the channel only as a last resortIX. Allow for changes authored by the riverX. Use appropriate personnel to scope and design restoration efforts.River RestorationContext, Context, ContextContext, Context, ContextSpatial: What kind of stream is it?Spatial: What kind of stream is it?Temporal: What is its disturbance history?Temporal: What is its disturbance history?River RestorationWhat kind of What kind of streamis it?is it?Braided, meandering, straight?Cascade, Step-Pool, Plane-Bed, Pool-Riffle?ChannelmorphologyBankmaterialFlowobstructionsValleyslopeConfinementSediment Water WoodRiparianvegetationRiver RestorationChannelmorphologyBankmaterialFlowobstructionsValleyslopeConfinementSediment Water WoodRiparianvegetationRiver RestorationWood in riversWood acts as an impediment to flow that can cause flow to converge and scour out pools that provide important habitatExtent of global forestsForests have covered about one-third of the Earth’s land surface during the Holocene.But the extent of forest cover has changed substantially ... Oregon AmazonCameroonFew of the worlds forests retain “frontier” conditionsMuch of our understanding of river systems was developed in areas that either lacked large wood or that had been cleared of wood debris.To what degree are our perceptions of the role of wood in rivers due to such historic legacies?Snags on the MissouriKarl Bodmer, circa 1850Log jams were significant obstacles to navigation and land development in the western U.S.02000400060008000100001880 1900 1920 1940 1960Snags/YearRivers & HarborsSkagit RiverAll RiversArmy Corps of Engineers aggressively “deArmy Corps of Engineers aggressively “de--snagged” American Riverssnagged” American RiversThousands of snags were removed from Puget Sound rivers between 1880 and the mid-20th CenturyChannel Unit ScaleGreater wood loading leads to more poolsFor channels we’ve surveyed in Alaska and Washington, a plane-bed morphology occurs only at low LWD loading1.51.00.50.005101520pool spacing (channel widths/pool)SE AlaskaNW Washingtonplane-bed pool-riffleLWD frequency (pieces/m)Reach ScaleLWD can control the formation of pools and bars, and thereby channel reach morphologyValley Segment ScaleLog jams trap copious amounts of sediment and aggrade entire reaches of channel.Valley Segment ScaleBoth locally recruited trees and log jams delivered by debris flows can create alluvial valley bottoms in confined mountain streams.A B100 m100 mLog jams can influence even large riversNISQSNOHSTILLPieces/KilometerJamsOtherPosition in Position in Channel NetworkChannel NetworkQueets River, WashingtonLog stepsBankfull benchMeander jamValley jamWatershed ScaleWatershed ScaleEffects of Wood in RiversSpatial scale (meters)11010010,00011001000In-ChannelPoolsCoverBankComplexityReachChannelSwitchingIslandsSloughsValley BottomWater,Sediment & Wood RoutingYearsHow big does a log have How big does a log have to be in order to influence to be in order to influence a river?a river?00.20.40.60.811.21.41.61.820 0.2 0.4 0 .6 0.8 1 1.2 1.4 1.6 1 .8 2log length / bankfull widthbasal diameter of bole / mean bankfull depthKey Racked LooseLog diameter / channel depthLog length / channel widthLWD Size and Channel Size Govern LWD Stability & InfluenceKeyLooseRackedRiver RestorationReintroduction of large woody debrisRestoration of “natural” wood loading would take centuries because of the time needed to grow large, “key member” logs that can shape aquatic habitat.ELJsELJs: Engineered Log Jams: Engineered Log JamsEngineered log jams are inEngineered log jams are in--stream stream flow control structures based on the flow control structures based on the architecture of naturally occurring, architecture of naturally occurring, stable log jams.stable log jams.Log Jam PlacementFloodplain channel dugLog PlacementCowlitz River Engineered Log Jams, 25 yr flood event 5 weeks after constructionChanges at the Cowlitz Site: 12/95 to 04/97Floodplain setbacksLevee relocation to allow floodway along rivers becoming increasingly popular as a restoration measureKissimmee River, FloridaRe-meandering, Undoing channelizationProvo River, UtahLower Duwamish River, SeattleRestored reach formerly in a straight culvert, Berkeley, CAUvas Creek, January 1996Uvas Creek, July 1997Uvas Creek “restoration” projectHam Creek, SeattleThornton Creek, SeattleUrban channelsFew opportunities for restorationCuyahoga River, 1952What does it take to design a restoration project?Should
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