From Salish Sea Wiki

Floodplain Icon.jpg


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

Wiki Rules

Link to List of Workgroups Link to List of Topics Link to List of Places

Link to List of Efforts Link to List of Products Link to List of Documents Link to List of Graphics Link to List of Websites

Link to Delta Sites Link to Embayment Sites Link to Beach Sites Link to Rocky Headland Sites

Link to Headwater Sites Link to Lowland Watershed Sites Link to Floodplain Sites

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 critical for Biodiversity and Salmon and are also vital for Agriculture. Encroachment of residential Land Use on floodplains is a driver for Flood Hazard Management. Floodplains are generally described by FEMA mapping of flood hazard areas. The Floodplains by Design effort by The Nature Conservancy of Washington aims to provide a stronger assessment of these systems. Lakes and Wetlands are all different kinds of floodplains (where shallow Groundwater is found at or near the surface for parts of the year).

Physical Context[edit]

USGS collaborates with NOAA to provide real-time data on river flow and flood stage. Mauger et al 2015 describes the anticipated change in the flow regime under Climate Change. 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[edit]

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

Planning Context[edit]

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.


The following topics are related to floodplains:


The following sites are in floodplains:


The following efforts are being implemented by workgroups in floodplains:


The following Documents use the Floodplain Category: