Stream Network Capacity to Support Beaver Dams, Tualatin River Basin, Northwest Oregon

Beaver dams can help streams connect to their floodplains. These floodplain connections can expand the range of available aquatic habitats and aid in the restoration of stream and floodplain processes. North American beavers (Castor canadensis) occupy a wide variety of aquatic habitats; however, their ability to build dams, the agent of stream and floodplain change, is constrained in large part by three physical variables—local vegetation, topography, and hydrology. These three physical variables are combined in the Beaver Restoration Assessment Tool (BRAT), a geographic information system-based utility that uses a Fuzzy Inference System (FIS) to estimate the capacity of each reach within a stream network to support beaver dams. In this study, version 1.0 of BRAT was adapted and applied to the perennial stream network of the Tualatin River Basin in northwestern Oregon. Estimates of dam density, or the number of beaver dams the landscape can support per kilometer, are reported in this data release as precise numbers, however, these results are often summarized categorically to better reflect the uncertainty in the estimates. Additional details can be found in the accompanying report, but categories used in the report are as follows: 0: "None"; 0-1; "Rare"; 1-4: "Occasional"; 5-15: "Frequent"; and 15-40: "Pervasive".

Associated report citation: 
White, J.S., Smith, C.D., Jones, K.L., and Rounds, S.A., 2025, Stream network capacity to support beaver dams in the Tualatin River Basin, northwestern Oregon, chap. A of Jones, K.L., and Smith, C.D., eds., Beavers in the Tualatin River Basin, northwestern Oregon: U.S. Geological Survey Scientific Investigations Report 2025–5039–A, 20 p., https://doi.org/ 10.3133/ sir20255039A.