Sauvie Island Floodplain Restoration

Constructed side channel on Sauvie Island

Wolf Water Resources (W2r) and our staff have delivered many projects from design to construction on Sauvie Island. Sauvie Island offers floodplain refuge habitat just downstream of the urban waterfront corridors on the Columbia and Willamette Rivers, but much of this habitat has been disconnected from tidal influence and is dominated by reed canary grass.

Recent work by W2r on Sauvie Island include the Crane, Domeyer, Willow Bar, and Flight’s End restoration projects. W2r has also created restoration designs for two sites at Burlington Bottoms, along the Multnomah Channel—Enyart and Palensky. On each project W2r worked closely with CREST, water conservation districts, and other partners to integrate multiple objectives related to site access, recreation, turtle habitat, bird habitat, and salmonid rearing habitat.

Recognizing that long-term channel stability is tied to geomorphic processes and local hydraulics across a wide range of flows,  we used geomorphic analysis to size tidal channel connections and emergent marsh tidal prisms for each site. To accurately simulate floodplain inundation and infiltration, we modeled infiltration losses during recession of the spring freshet. For the Flight’s End site, we developed an approach to preserving popular waterfowl wetlands while providing salmonid access by using beaver dam analogues at strategic elevations (based on water levels and temperature to avoid stranding). Our hydraulic modeling of the Palensky site simulated the effect of beaver dams across the floodplain as a means to preserve turtle and frog habitat. Designs for each site promote the establishment of native plant communities in order to replace reed canary grass meadows with a self-maintaining channel and tidal wetland systems.

Construction of the Crane, Domeyer, and Willow Bar sites has been completed. Designs for the Palensky, Enyart (McCarthy Creek), and Flight’s End sites were expedited two weeks ahead of schedule, enabling CREST to bid the project early for better prices and manage their internal workload. Despite the progressive schedule, W2r maintained quality in our plan sets—our client commenting that the plans received very few requests for clarification from construction contractors.