South Beaver Creek Natural Area Restoration Troutdale, Oregon
As part of an effort by regional government Metro to identify and acquire parcels of land that present opportunities to protect and restore ecologically significant greenspaces, this natural area along Beaver Creek in the east suburbs of Portland, Oregon is enhanced to benefit local ecology and the surrounding community. In leading the restoration design, Otak took a unique approach using a 2D no-rise analysis and helicopter placement of large wood that aimed to provide new habitat and return the watershed to a more naturally functioning state.
Adding Channel-Spanning, Large Log Root Wads to Restore a Stream’s Floodplain
Flowing directly into the Sandy River – a tributary to the Columbia River – Beaver Creek provides important habitat for salmonids, including endangered Coho Salmon, as well as lamprey. This site contains two crossings where small culverts historically didn’t allow the transport of large wood and sediment into the reach that would naturally occur, limiting in-stream habitat conditions for rearing juvenile salmonids and the ability of Beaver Creek to fully express itself in the watershed. Following the replacement of those culverts, this project was designed to jump start the habitat creation process and provide immediate refugia for salmonids. The project also removed a mid-reach fish barrier – an abandoned concrete flashboard weir – that yielded shallow sheet flow conditions during summer months and high velocity flow in the winter, both challenging situations for fish. Using multiple channel-spanning large wood structures provides opportunities for beaver to add dams, the creation of scoured pools for salmonid habitat, and an overall more complex system where new channels can form and potentially reactivate old flood paths. In support of the floodplain permitting process, 2D hydraulic modeling helped ensure an understanding of site parameters and identify wood placement locations, while also making the permitting process feasible.
Due to the size of the creek and wood needed, the opportunity of employing an unusual technique for a less remote location was taken in construction. The unanchored large wood placement by a Vertol helicopter allowed the team to avoid disruption to the floodplain from the typical use of heavy machinery. The cost-effective and environmentally-friendly design utilized wood debris that could be both air lifted and sufficiently sized to self-stabilize in this reach of the greenway.
