DESCRIPTION
Downey Creek is a highly productive tributary to the Suiattle River that in recent years has provided 20-40% of the Spring Chinook spawning in the Suiattle River basin. Due to high natural turbidity only very limited spawning occurs in the main Suiattle River, so the lower-gradient areas of large, clear water tributaries such as Downey Creek provide unique and important habitat.
The Forest Service Suiattle River Road previously crossed Downey Creek with a 115 foot long cast-in-place box girder bridge at milepost 20.9. The roadway was constructed on an elevated embankment that restricted flow and channel formation across the Downey Creek alluvial fan. Immediately downstream of the bridge, Downey Creek flows into the floodplain of the Suiattle River, where it continues for approximately 1200 feet in an historic channel before entering the Suiattle River.
This project restored the alluvial fan of Downey Creek by removing the roadway embankment and adding three 70 foot bridge spans to the pre-existing bridge for a total span length of 325 feet. This restored the natural process of channel migration and side channel formation on the alluvial fan of Downey Creek, improved conditions in a side channel, and restored connectivity between Downey Creek and the Suiattle River floodplain. This improved Chinook salmon habitat in this relatively rare and important habitat.