Initial Responses of Riparian Vegetation and Wetland Functions to Stage 0 Restoration of Whychus Creek, Oregon

Floodplain disconnection caused by anthropogenically-triggered channel incision or artificial levee construction, has led to widespread loss of riparian habitat and ecosys-tem functions in river systems across the globe. Restoring connectivity is now consid-ered essential to recover lost biodiversity and improve water quality, yet evidence for the ecological outcomes of full reconnection remains limited. This study evaluates the ecological effectiveness of two Stage 0 restoration projects on Whychus Creek, Oregon, which reestablished stream–floodplain connectivity across the entire valley floor in 2012 and 2016, respectively. We used pre- and post-restoration vegetation surveys along fixed transects to assess changes in plant assemblages and compared these with an unre-stored reach and a reach restored six years earlier. Two years after the restoration was carried out, the active riparian area had expanded 2.5-fold and supported a patchy, shifting mosaic of aquatic, wetland, riparian, mesic, and upland habitats. Species rich-ness and structural diversity increased significantly. We also saw found improvements in key wetland functions such as water storage, sediment retention and nutrient cycling – evidence of healthy, heterogenous habitats that can support a wide range of species. Our results show that Stage 0 restoration can rapidly reestablish complex habitat net-works and deliver diverse ecological benefits. Continued monitoring is essential to as-sess the long-term trajectories of post-restoration succession and resilience. This study contributes to the growing evidence base for process-based restoration that pri-oritizes full floodplain reconnection in anthropogenically-incised rivers.