Restorative Flood Protection
Restorative Flood Protection is intended to rebuild some of the lost natural flood storage capacity of the Chehalis Basin upstream of Chehalis, by reversing landscape changes that contribute to downstream flooding and erosion. The flood storage capacity of the Chehalis Basin would be increased by adding engineered large wood structures and plantings to create “roughness” (or resistance to flow) in river and stream channels and the floodplain, and by reconnecting river channels to floodplain storage. Restorative Flood Protection would reduce flood peaks on the Chehalis River downstream of the confluence with the Newaukum River, which is where the greatest flood damages have historically occurred. There are about 140 river miles (RMs) within the Restorative Flood Protection treatment area, and the associated floodplain area that is engaged by these rivers during a 100-year flood is about 21,000 acres. To attain downstream reductions in flooding, large areas of valley bottom land in treatment areas would be converted from agricultural, residential, and commercial land uses to river management corridors or greenways where flooding would occur more frequently than it currently does. This action would be dependent upon landowner willingness and would reduce flood damage downstream of the Newaukum confluence, including Centralia and Chehalis. This option is currently being explored for feasibility and is not being implemented at this time.