ABSTRACT
ABSTRACT: The Chehalis River basin in southwest Washington State, USA, has a long history of flooding. These floods have caused severe hardship for the residents of the basin, and have included the closure of the major north-south transportation route from Washington to California. For years, various agencies have considered a range of flood reduction and flood warning measures. Recently, a number of studies have been done to look at early flood warning, hydrologic and hydraulic modeling for flood reduction and habitat restoration studies, and the potential impacts on fish habitat and fish passage from alternative flood reduction projects. Alternatives considered have included an upstream retention dam, levees around the Twin Cities and regional airport, and levees along Interstate 5. This paper discusses the various basin-wide studies undertaken to reduce flood impacts, increase flood warning, and environmental assessments that are designed to maintain the rivers fisheries and environmental restoration activities. This work is ongoing as studies continue to examine flood control alternatives, and the effects of a potential upstream impoundment on fish habitat and populations.
