Wally MacFarlane, USU
Carl Saunders, ELR
Joe Wheaton, USU
Pete McHugh, ELR
Eric Wall, ELR
Chris Jordan, NOAA
Beaver are becoming more broadly appreciated for their utility as an ecosystem engineer capable of restoring streams, rivers, and wetlands to the benefit of numerous flora and fauna, including salmon and steelhead (Bouwes et al. 2016). Recently, Utah State University collaborated with ISEMP to develop a spatially explicit network model called the Beaver Restoration Assessment Tool (BRAT) to help assess the potential for using beaver as a stream conservation and restoration agent at the watershed scale.
BRAT models the capacity of the landscape to support dam-building activity by beaver (Macfarlane et al. 2017). Capacity estimates come from five main lines of evidence:
- a reliable water source
- stream bank vegetation conducive to foraging and dam building
- vegetation within 100 m of edge of stream to support large beaver colonies
- likelihood that dams could be built across the channel during low flows
- the likelihood that a dam is capable of withstanding typical floods
For assessment, BRAT combines information on: A) existing and historic capacity, B) riparian habitat condition and recovery potential, and C) probabilities of potential conflict with humans, and then assigns stream segments into different beaver conservation and restoration categories (see figure). BRAT has been run with widely available existing GIS datasets across the interior Columbia River Basin (http://brat.joewheaton.org/).
Findings and Uses
BRAT’s beaver dam density and total maximum dam capacity estimates compare favorably to actual distributions, even across a large, climatically and physiographically diverse landscape where water and/or wood may be locally limiting.
BRAT helps assess where beaver may be a viable restoration tool or where they may be seen as a nuisance requiring mitigation or relocation.
Bouwes, N., N. Weber, C. E. Jordan, W. C. Saunders, I. A. Tattam, C. Volk, J. M. Wheaton, and M. M. Pollock. 2016. Ecosystem experiment reveals benefits of natural and simulated beaver dams to a threatened population of steelhead (Oncorhynchus mykiss). Scientific Reports 6:28581.