Floodplains

Floodplain

Floodplains occur where large rivers and streams meander in their own sediments

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• Ecology Coastal Oblique Photography
• The Encyclopedia of Puget Sound provides a peer reviewed version of the wiki
• The Nearshore Map Portal
• Habitat Work Schedule Map
• PRISM Project Search
• Washington Coastal Atlas

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Floodplains form where rivers flow through a valley of alluvial sediment several times the width of the channel. During floods, the river inundates the floodplain depositing sediments. Floodplains and their rivers are fed by both headwaters and lowland watersheds, and flow into river deltas as they enter the sea. Floodplains are generally described by FEMA mapping of flood hazard areas. The Floodplains by Design effort by The Nature Conservancy of Washington is anticipated to provide a stronger assessment of these systems. Lakes, ponds and wetlands are all different kinds of floodplains (where shallow ground water is found at or near the surface for parts of the year).

Physical Context

USGS collaborates with NOAA to provide real-time data on river flow and flood stage. Mauger et al 2015 describes anticipated change in flow regime. Rivers are flows of both water and sediment and Czuba et al 2011 summarizes existing data on total sediment budget. Collins & Montgomery 2011 describes a diversity of physical systems, based on how much, and how floodplains have filled since glacial excavation.

Biological Context

Besides us, beaver are key ecosystem architects, and reduction in beaver populations combined with flood hazard management have radically changed floodplain ecosystems.

Planning Context

Because of our dry-summer climate, moist rich floodplain soils are vital to agriculture. The Puget Sound Partnership has adopted a floodplain restoration target as part of Puget Sound Vital Signs. Floodplains by Design has promoted multi-benefit restoration strategies, with novel efforts in the Puyallup/White. Snohomish, Stillaguamish, Skagit, Nooksack, Dungeness and Skokomish basins. Floodplain habitats. The Puget Sound Watershed Characterization identified a unique set of floodplain attributes because of wetlands, including those created by beaver, re-affirming the importance of floodplains already described in salmon recovery planning, particularly for endangered Puget Sound Chinook Salmon. A constellation of authorities and agencies in Flood Hazard Management systems are focused on floodplain dynamics.

Floodplain Topics

The following topics are related to floodplains:

• Engineered Log Jams
• Flood fencing
• Riparian Buffers
• Channel migration zone
• Flood Hazard Management
• Snohomish Agricultural Resilience
• Beaver
• Snohomish Agriculture Resilience Plan
• Integrated Floodplain Management
• Rivers and Harbors Act

Floodplain Sites and Places

The following sites are in floodplains:

• South Fork Nooksack Floodplain
• Lower Skykomish Floodplain
• Lower Stillaguamish Floodplain
• North Fork Nooksack Floodplain
• North Fork Stillaguamish Floodplain
• Tolt River Floodplain
• Skokomish Confluence
• Sammamish River Floodplain
• French Slough Floodplain and Watershed
• Snohomish Lord Hill Reach
• The Marshlands
• Lower Snohomish River Floodplain
• South Fork Stillaguamish Floodplain

Floodplain Efforts

The following efforts are being implemented by workgroups in floodplains:

• Floodplains by Design (FbD)
• Elwha Dam Removal
• Lower Canyon Creek Restoration
• Coastal Resilience to Climate Change
• Working Buffer Pilot Project
• Scatter Creek Farm and Conservancy
• Farmhouse Reach Floodplain Restoration
• Black River Farm
• Nooksack Floodplain Restoration with Engineered Log Jams
• Larson's Reach Floodplain Restoration
• Jim Creek Channel Enhancement
• Old Soldiers Home Levee Setback
• Pierce County Levee Setback Planning
• Skykomish Habitat Mitigation Bank
• French Slough Drainage Management
• Lower Snohomish Reach Scale Plan
• Lower Skykomish Floodplain Design
• Haskell Slough Protection and Restoration
• Skagit Farmland Legacy Program
• Lower Skykomish Reach Scale Plan
• Snohomish County River Atlas
• Skykomish Braided Reach Project
• Whatcom Drainage Maintenance Guidance
• Nooksack Floodplain Integrated Management Planning
• Predicting Sea Level Rise Impacts on Ag Production
• Barnaby Reach Restoration
• The Ecosystem Guild/Bio-Cultural Restoration Field Stations
• Snoqualmie Fish, Farm and Flood Initiative

Floodplain Documents

The following pages cite documents about floodplains:

• Yang et al 2011 model flood and tide
• File:Breslow 2001 farmer perception of salmon recovery.pdf
• File:Maudlin & Coe 2011 SF Nooksack ELJ effectiveness.pdf
• Pess et al 2011 salmon density on Elwha ELJs
• File:KWL 2003 canyon creek alluvial fan risk assessment.pdf
• File:Herrera 2007 canyon creek restoration plan.pdf
• File:DeVries 2010 lower skykomish geomorphic analysis.pdf
• File:NHC 2006 skykomish snoqualmie flood insurance report.pdf
• File:Benedict & Shaw 2012 shade benefits from hedgerow on ditched streams.pdf
• File:Earth Economics 2013 pierce county flood return on investment.pdf
• File:Roni et al 2013 DRAFT BPA columbia river restoration monitoring plan.pdf
• File:STNRD 2011 sediment impact on artificial chinook redds north fork stillaguamish.pdf
• File:Knutson & Naef 1997 riparian management recommendations.pdf
• File:May 2003 riparian best available science puget lowland.pdf
• File:Rapp & Abbe 2003 channel migration zone.pdf
• File:Boggs & Corey 2009 whatcom drainage maintenance plan.pdf
• File:Dean 2011 farm succession strategies.pdf
• Konrad 2015 ecological function flood risk puget sound floodplains
• File:Pollock et al 2015 beaver restoration guidebook.pdf
• Beechie et al 2010 process based restoration of rivers
• File:Arcos 2012 skokomish channel stability.pdf
• File:Canty et al 2012 farmland protection puget sound.pdf
• File:FCWMC 2004 french creek watershed management plan.pdf
• File:Hass 2001 snohomish ecosystem restoration opportunities.pdf
• File:Leonetti et al 2015 north fork stillaguamish habitat change.pdf
• Collins et al 2002 historical wood in large rivers
• Collins & Montgomery 2002 restoring wood in river floodplains
• File:GeoEngineers 2008 puyallup basin levee setback feasibility.pdf
• File:FEMA 2013 model floodplain ordinance NFIP and ESA.pdf
• File:FEMA 2013 environmental benefits acquisition hazard mitigation.pdf
• File:Brown 2015 DRAFT nooksack floodplain vision and implementation.pdf
• File:Cereghino 2015 coordinated investment snohomish framework.pdf
• File:Evans & Moore 2011 snohomish sustainable lands strategy framework.pdf
• File:WDFW 2015 french creek drainage maintenance HPA.pdf
• Collins & Montgomery 2011 puget sound floodplain domains
• File:SCSWM 2012 middle pilchuck river assessment.pdf
• File:SCSWM 2012 pilchuck river geomorphic assessment.pdf
• File:Mauger et al 2016 climate change and floodplain decision support.pdf
• File:CIG 2016 climate change in floodplains.pdf
• File:DeVries 2015 lower snohomish geomorphic assessment.pdf
• File:USACE 2000 stillaguamish restoration feasibility.pdf
• File:Turner et al 2004 stillaguamish flood hazard management plan.pdf
• File:Klesick 2016 DRAFT SVPI concept.pdf
• File:SCD 2016 lower stilly farmland use map.pdf
• File:Cereghino 2016 DRAFT lower stillaguamish context.pdf
• File:SnoCo 2014 DRAFT lower skykomish reach scale plan.pdf
• File:Brouwer et al 2015 floodplain early opportunities.pdf
• Legg & Olson 2015 identifying migrating stream channels in GIS
• Snohomish County 2015 hazard mitigation plan
• File:Mauger & Kennard 2017 climate change and flood hazard management.pdf
• File:Cereghino 2017 DRAFT riparian framework.pdf
• File:Boggs & Corey 2009 whatcom drainage maintenance guidance.pdf
• Abbe et al 2018 design and placement of engineered log jams
• File:Habitat Strategic Initiative 2021 estuary and floodplain implementation strategy.pdf
• File:Wright 2021 integrated floodplain management puget sound.pdf
• File:Beechie et al 2017 salmon habitat status monitoring.pdf
• File:Mauger et al 2015 snohomish downscale hydrologic projections.pdf
• File:Cardno 2020 lower skykomish channel migration zone.pdf
• Abbe & Montgomery 2003
• Roni et al 2015 wood placement summary
• Montgomery et al 2003
• File:McHenry et al 2007 ELJ monitoring elwha river.pdf
• File:Katz et al 2022 flood attenuation and restoration puyallup white.pdf
• Naiman et al 2010 process-based floodplain forest patterns
• File:Biddle et al 2022 national strategy protect restore floodplain wetland function.pdf
• File:FEMA 2011 floodplain habitat assessment mitigation.pdf
• Skidmore & Wheaton 2022 riverscapes as adaptation infrastructure
• File:Booth et al 2021 lower skykomish geomorphic assessment.pdf
• File:WSE 2021 snohomish hydrologic and hydraulic modelling.pdf

The following floodplain documents are uploaded to this wiki:

• Breslow 2001 farmer perception of salmon recovery.pdf
• Maudlin & Coe 2011 SF Nooksack ELJ effectiveness.pdf
• KWL 2003 canyon creek alluvial fan risk assessment.pdf
• Herrera 2007 canyon creek restoration plan.pdf
• DeVries 2010 lower skykomish geomorphic analysis.pdf
• NHC 2006 skykomish snoqualmie flood insurance report.pdf
• Benedict & Shaw 2012 shade benefits from hedgerow on ditched streams.pdf
• Earth Economics 2013 pierce county flood return on investment.pdf
• Roni et al 2013 DRAFT BPA columbia river restoration monitoring plan.pdf
• STNRD 2011 sediment impact on artificial chinook redds north fork stillaguamish.pdf
• Knutson & Naef 1997 riparian management recommendations.pdf
• May 2003 riparian best available science puget lowland.pdf
• Rapp & Abbe 2003 channel migration zone.pdf
• Boggs & Corey 2009 whatcom drainage maintenance plan.pdf
• Dean 2011 farm succession strategies.pdf
• Pollock et al 2015 beaver restoration guidebook.pdf
• Arcos 2012 skokomish channel stability.pdf
• Canty et al 2012 farmland protection puget sound.pdf
• FCWMC 2004 french creek watershed management plan.pdf
• Hass 2001 snohomish ecosystem restoration opportunities.pdf
• Leonetti et al 2015 north fork stillaguamish habitat change.pdf
• GeoEngineers 2008 puyallup basin levee setback feasibility.pdf
• FEMA 2013 model floodplain ordinance NFIP and ESA.pdf
• FEMA 2013 environmental benefits acquisition hazard mitigation.pdf
• Brown 2015 DRAFT nooksack floodplain vision and implementation.pdf
• Cereghino 2015 coordinated investment snohomish framework.pdf
• Evans & Moore 2011 snohomish sustainable lands strategy framework.pdf
• WDFW 2015 french creek drainage maintenance HPA.pdf
• SCSWM 2012 middle pilchuck river assessment.pdf
• SCSWM 2012 pilchuck river geomorphic assessment.pdf
• Mauger et al 2016 climate change and floodplain decision support.pdf
• CIG 2016 climate change in floodplains.pdf
• DeVries 2015 lower snohomish geomorphic assessment.pdf
• USACE 2000 stillaguamish restoration feasibility.pdf
• Turner et al 2004 stillaguamish flood hazard management plan.pdf
• Klesick 2016 DRAFT SVPI concept.pdf
• SCD 2016 lower stilly farmland use map.pdf
• Cereghino 2016 DRAFT lower stillaguamish context.pdf
• SnoCo 2014 DRAFT lower skykomish reach scale plan.pdf
• Brouwer et al 2015 floodplain early opportunities.pdf
• Mauger & Kennard 2017 climate change and flood hazard management.pdf
• Cereghino 2017 DRAFT riparian framework.pdf
• Boggs & Corey 2009 whatcom drainage maintenance guidance.pdf
• Habitat Strategic Initiative 2021 estuary and floodplain implementation strategy.pdf
• Wright 2021 integrated floodplain management puget sound.pdf
• Beechie et al 2017 salmon habitat status monitoring.pdf
• Mauger et al 2015 snohomish downscale hydrologic projections.pdf
• Cardno 2020 lower skykomish channel migration zone.pdf
• McHenry et al 2007 ELJ monitoring elwha river.pdf
• Katz et al 2022 flood attenuation and restoration puyallup white.pdf
• Biddle et al 2022 national strategy protect restore floodplain wetland function.pdf
• FEMA 2011 floodplain habitat assessment mitigation.pdf
• Booth et al 2021 lower skykomish geomorphic assessment.pdf
• WSE 2021 snohomish hydrologic and hydraulic modelling.pdf

particles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment.