Estimates of Changing Daily Precipitation Intensity and Flood Risk in the Pacific Northwest Using Regional Climate Simulations
May 2010 - June 2011
- Corps of Engineers
The study will provide crucial data resources to support ongoing biological research in both terrestrial and aquatic ecosystems affected by high flows. These include extensions of current research on aquatic ecosystems impacted by river scour, channel morphology, and influx of woody debris (e.g. associated with the 20-year flood). Changing sediment source and transport regimes in watersheds experiencing the combined effects of potentially changing precipitation intensity, retreating glaciers, loss of snowpack, changing fire risks, and vegetation changes are important factors affecting coastal ecosystems in sensitive rivers such as the Skagit and Nisqually Rivers in the Puget Sound basin. Likewise, impacts to primary productivity in the coastal ocean are linked to sediments and associated nutrients delivered primarily by high flow events. Aquatic ecosystem impacts related to landslides and culvert failure in forest roads within National Park boundaries ultimately affect instream habitat for aquatic biota, and evaluations of species recovery efforts, especially for salmonids. Flooding is an important factor affecting terrestrial wetlands and is the subject of studies examining impacts to amphibians. At large spatial scales, the effects of changing flood risk in the Columbia River basin (and potential changes in water management for flood control) are both important inputs to ecosystem models used by the National Marine Fisheries Service (and others) to assess salmon recovery plans. Some collaborating federal and state agencies involved in these efforts include the U.S. Geological Survey, National Marine Fisheries Service, The Nature Conservancy, American Rivers, Trout Unlimited, U.S. National Park Service, U.S. Fish and Wildlife Service, WA State Dept. of Ecology, Skagit River System Cooperative, Northwest Power and Conservation Council, U.S. Bureau of Reclamation, U.S. Army Corps of Engineers. Scope of Work 1. Analyze ensemble of regional climate simulations to detect changes in extreme events relevant to flood risk. This analysis would include parameters such as changes in precipitation intensity, storm inter-arrival times, frequency of rain-on-snow, etc. 2. Develop and refine downscaling approaches for application to the regional climate model 3. Create daily time stephydrologic model driving data sets for selected future time periods based on downscaled regional climate model simulations 4. Run and archive hydrologic model simulations 5. Estimate associated flood risk for 297 CBCCSP sites 6. Create web-based archive of results. 7. Publish a journal article.