Willamette Basin Floodplain Inundation Mapping (NEW)
Watershed and Stream Assessments
Client / Agency
Meyer Memorial Trust and The Nature Conservancy
Meyer Oregon Watershed Enhancement Board, Oregon State University, University of Oregonvancy
Willamette River, Middle Fork and Coast Fork Willamette River, McKenzie River
2010 - 2013
River Design Group, Inc. (RDG) with funding provided by the Meyer Memorial Trust (MMT) and The Nature Conservancy (TNC), collaborated with a Technical Team comprised of representatives from MMT, TNC, Oregon Watershed Enhancement Board, Oregon State University, University of Oregon, and Bonneville Education Foundation to facilitate mapping the regulated 2-year discharge on a 160 mile reach of the Willamette River and 60 miles of the Middle Fork and Coast Fork Willamette River and the McKenzie River.
Eleven flood control dams and two flow regulating dams manage tributary flows to the Willamette River. Constructed between 1942 and 1968, the dam network has been instrumental in reducing flooding in the Willamette Valley, allowing agricultural and residential development of low-lying properties. However, flood control operations in addition to other channel simplification measures such as channel clearing and streambank armoring, and alteration of the historical floodplain, have affected river processes and ecological function of the Willamette River.
The goal of the Willamette Basin Floodplain Inundation Mapping Project is to estimate the extent of floodplain inundation associated with the regulated 2-year discharge on the Willamette River and key Cascade Range tributaries by using LiDAR datasets, hydrologic data and a “bath tub” method hydraulic analysis. The regulated 2-year discharge was selected as a frequent flow that has ecological importance for fish inhabiting the Willamette River system. Report and map deliverables completed for each water body are anticipated to be used as tools for identifying potential floodplain restoration areas, locating possible obstructions to river-floodplain habitat interaction, and assisting fisheries managers with locating possible floodplain refugia habitats for native fish species including federally-listed spring Chinook salmon.