Article Alert: #Beaver #Restoration Assessment Toolkit in press at #Geomorphology
In the spring of 2013 I sat down with Wally Macfarlane, Martha Jensen, Joe Wheaton, and a handful of others and we walked through an early workflow for what is now the Beaver Restoration Assessment Toolkit (BRAT). The idea for BRAT was simple: using basic hydrologic and riparian vegetation metrics, scientists and planners can estimate where along a stream network beaver dams will be able to persist. What if there was a tool that used widely available, free data to estimate dam capacity across entire watersheds? What might it tell land managers, many of whom are considering beaver management as a part of their watershed management and restoration plans?
One major benefit to knowing where beaver dams can be built and persist is for planning beaver relocation and stream restoration. By building hypotheses about where beaver will successfully be able to build dams, land managers can more successfully move beaver from problem areas like urban and irrigation infrastructure to conservation areas. Across Utah and the North American West, many of these conservation areas include streams where beaver and their dams have been removed. This beaver loss has altered water and sediment movement that historically created and maintained step-pool complexes or alluvial valley bottom meadows, and increased streamflow duration. Beaver removal, which caused dam loss, often occurred as Europeans settled the West. In some cases, human land-use also led to direct dam removal that changed channel slope and allowed channels to incise, lowering the stream bed until floodplain disconnection was inevitable.
|A little incision following long-term grazing, UT, USA|
The EPA's wadeable stream assessment estimated that 41% of the West's streams are in poor shape, many of which have been modified for human land use that led to beaver and beaver dam loss.
|In short, many U.S. streams are in sub-optimal shape. Source, EPA Wadeable Streams Assessment|
Now, given the condition of most of the West's streams (see below), we know that there is a need for a flexible restoration planning tool that anyone can use - tribes, state and federal agencies, and local watershed planners. Wally and Joe dreamed up a framework that uses LANDFIRE data and NHD stream segments to estimate beaver dam capacity based stream power and vegetation types. If a stream is perennial and not so large and powerful that it blows out dams at an average flood discharge, then it might support dams. If the riparian vegetation within a reasonable distance of the stream is of a preferred type (i.e. a type that beaver can readily eat and use in constructing dams), then beaver can probably build more dams than if the vegetation is sparse or a low quality material for dam building. Areas with gallery cottonwood forests and/or willow thickets are probably better for building dams than sagebrush or cheatgrass. So, if beaver have enough water, but not too much, and a good vegetation source, they can build dams, dams that have a variety of ecological benefits.
Using these relatively obvious concepts, Wally and Joe labored for years alongside an army of technicians and other hydrologists, ecologists and geomorphologists, including Nic "big body" Bouwes, Martha "Superwoman" Jensen, Jordan "GIS" Gilbert, John "I don't know him well enough for a clever nickname" Shivik, and I. From 2013 to 2015, we all either applied this framework to small watersheds, fine-tuning our methods and interpretations, or used model outputs to implement and assess stream restoration projects. We all wrote and interpreted results, and Martha and Wally made some absolutely gorgeous figures. Much of this work came out in large, unwieldy technical reports or was assimilated into the tutorial website at brat,joewheaton.org.
The resulting manuscript came out earlier this month and explains the rationale for the model and its applications, synthesizing the condition of many Utah streams relative to their potential to retain beaver dams that might restore those suffering from historic floodplain disconnection. Many streams where beaver have been removed currently have far fewer beaver dams than the landscape can support. Utah has serious upside potential to restore stream-floodplain connectivity, riparian vegetation, and aquatic habitat diversity through beaver and their dams. This manuscript synthesizes those model results and provides examples in physiographically diverse watersheds where beaver relocation is being considered for stream and riparian habitat restoration. I encourage you to check it out at Geomorphology.
Macfarlane, W.W., J.M. Wheaton, N. Bouwes, M.L. Jensen, J.T. Gilbert, N. Hough-Snee, J.A. Shivik. In Press. Modeling the capacity of riverscapes to support beaver dams. Geomorphology. DOI: 10.1016/j.geomorph.2015.11.019
Free, publicly-available PDF at Researchgate
See additional BRAT reports, instructional videos and applications at brat.joewheaton.org.