Methods to Predict Beaver Dam Occurrence in Coastal Oregon

Pools provided by beaver( Castor canadensis) contribute to critical habitatrequirements of salmonids in fluvial systems of the Pacific Northwest, therefore more land managers are interested in managing watersheds that include beaversor engaging in beaver-related restoration projects. We evaluated the utility of applying an existing beaverhabitat suitability modelto better understand beaver damsite characteristics in coastal Oregon, identify optimum dam site locations, and guide future beaver-related restoration efforts. We used a combination of t-tests, Wilcoxon rank sum tests, and a stepwise discriminant function analysisto examine stream habitat associations with field data collected at known and predicted dam sites at reach and pool/ rifflelevels. We found bank-full width, valley floor width, and channel gradient performed well in predicting dam locations across the Alsea River Basin. Known dam sites had wider valley floors, shallower shoreline slopes, and fewer larger, deeper pools than predicted sites. Overall, our results suggest the beaverhabitat suitability modelcombined with a digital elevation model can be used to guide where beaver damsmay occur within the Alsea River Basin, yet they do not capture fine scale habitat associations that may lead to a settling response in beavers. For example, presence of large deep pools may be necessary for beaversto escape predation before and during dam building. Results from our study may be used to prioritize potential dam sites in other coastal basins that have similar geomorphic characteristics.