The importance of floodplains to functioning river ecosystems Photo courtesy of Tim Abbe Taiya river, ak abbe.jpg Today’s talk • What is a floodplain? • What features are associated with floodplains? • Why are floodplains important to aquatic ecosystem function? • How do we disturb and alter floodplains? • How do we restore floodplains? What is a floodplain? • Geomorphology– Flat, depositional feature of river valley – Adjoins river channel – Formed under current climate regime • Hydrology– Land subject to 100 year flood event figure 1a Photo and schematic courtesy of Tim Abbe healthy forest river coordors abbe.jpg What is a floodplain? • Ecology– Areas periodically flooded by lateral overflow of river or lakes. – Biota respond to change in environment• Individual • Community Schematic courtesy of Petersen and Reid 1984 petersen and reid first.jpg petersen and reid second.jpg What features are associated with floodplains? • Main channels • Logjams • Meander bends & scrolls • Floodplain channels • Beaver ponds • Mid-channel islands sauk 1996u sauk meander jam sauk sc7 sauk sc bp Why are floodplains important to ecosystem function? IMG_0639 Photo courtesy of Lauren Rogers Duwamish1995 Photo courtesy of Dave Montgomery Repository of water, wood, sediment, & nutrients Hunts road channel hunts road v Mainstem Pesset al. 2008 Flow North Lower Elwha River floodplain Attenuate peak flows 1980 Skagit River flood example development_within_floodplains_1970_2010_parcels_v4.tif Slide courtesy of Dan Sieman, NWF Increased residence time of water, wood, & nutrients Jeffreset al. 2008. Ephemeral floodplain habitats provide best growth conditions for juvenile Chinook salmon in a California river. Environmental Biology of Fishes Dashed line –discharge, light grey –river, solid black -floodplain Greater habitat use by salmonids pess et al figure 7 smaller .jpg Clear = main stem Black filled = floodplain Pesset al. 2008 Pre Dam Removal SC Source Extended Groundwater Better condition factor for outmigratingsalmonids Below floodplain Floodplain Jeffreset al. 2008Enclosed experiment, same age Chinook How do we disturb and alter floodplains? IMG_0639 Photo courtesy of Lauren Rogers Duwamish1995 Photo courtesy of Dave Montgomery Levees alter flow patterns & vegetative succession AbbeDisturbedChannel2 AbbeGoodChannel2 figure 1a T.Abbe WalwallaFlood1964USGS T.Abbe Walla Walla ~ 1960s Floodplain development can lead to loss or isolation of floodplain habitats collins skagit 1860.jpg collins skagit 1950.jpg Figures courtesy of Brian Collins –University of Washington Floodplain habitat isolationdiffer by basin Pesset al. 2003, Beechieet al. in prep How do we restore floodplains? IMG_0639 Photo courtesy of Lauren Rogers Duwamish1995 Photo courtesy of Dave Montgomery Pautzke_photopoints2.jpg Revetment removal & buried setback leveePautzkeProject –Green River Revetment removal & buried setback leveePautzkeProject –Green River Pautzke_photopoints.jpg F:\latterellj\Pautzke Project\Monitoring\Photo Points\Photo Point 03\pp03_a_2009.JPG August 14, 2009 Photos courtesy of Josh Latterell, King County Photo point #3 F:\latterellj\Pautzke Project\Monitoring\Photo Points\Photo Point 03\pp03_a_021611.JPG February 16, 2011 Photos courtesy of Josh Latterell, King County Photo point #3 F:\latterellj\Pautzke Project\Monitoring\Photo Points\Photo Point 04\pp04_a_2009.JPG August 14, 2009 Photos courtesy of Josh Latterell, King County Photo point #4 F:\latterellj\Pautzke Project\Monitoring\Photo Points\Photo Point 04\pp04_a_16Feb2011.JPG February 16, 2011 Photos courtesy of Josh Latterell, King County Photo point #4 Summary • What is a floodplain?– Geomorphic – Hydrologic – Ecological • What features are associated with floodplains?– Slower water areas, accompanying vegetation & obstructions • Why are floodplains important to aquatic ecosystem function?– Repository and increased residence time of water, wood, & nutrients – Attenuate peak flows, enhance low flows – Slower water environments for juvenile salmonidsduring critical times of their life cycle • How do we disturb and alter floodplains?– Isolate or disconnect the floodplain from its main channel • How do we restore floodplains?– Allow for main stem to access floodplain during a suite of flow events – Allows for natural processes of sedimentation and erosion Resources • Historic floodplain conditions– http://riverhistory.ess.washington.edu/ • Examples of floodplain restoration efforts– ToltRiver• http://www.kingcounty.gov/environment/animalsAndPlants/restoration-projects/tolt-restoration.aspx – Chinook Bend, Snoqualmie River –• http://www.kingcounty.gov/environment/waterandland/natural-lands/ecological/chinook-bend.aspx – Preston, Raging River –• http://www.kingcounty.gov/environment/waterandland/natural-lands/ecological/raging-river-plan.aspx