The Boulder County Parks & Open Space Department offers grants for research on county open space lands each year. All proposals are reviewed by a team of resource specialists, and awarded research projects are monitored during their activities on open space.
The following is a summary of a 2019 study conducted by Julianne Scamardo and Ellen Wohl at Colorado State University in Fort Collins. Their project assessed the potential for beaver restoration and likely environmental benefits.
Abstract
In 2017, Boulder County Parks & Open Space (BCPOS) and the City of Boulder Open Spaces and Mountain Parks (OSMP) jointly funded an inquiry into the potential for Boulder County streams to support North American beavers. The resulting study includes a literature review into the benefits and habitat requirements of beaver as well as original research on the potential for streams to support beaver dams in Boulder County. Research included site visits to BCPOS and OSMP properties and remote characterization of potential habitat. The field study utilized a checklist approach to assess suitability for either beaver reintroduction or construction of beaver dam analogs. The remote characterization, which was conducted for the entire St. Vrain watershed stream network, uses the beaver restoration assessment tool (BRAT) model based on physical and vegetative characteristics of stream segments to predict potential habitat suitability.
From both modeling and site visits, the BCPOS streams with the highest potential for successful beaver reintroduction are Delonde and Sherwood Creeks, and the OSMP streams with the high potential are Coal and South Boulder Creeks. According to hydrologic models created for segments of Delonde and Sherwood Creeks, the addition of a couple of beaver dams could increase inundated area by up to 537% at baseflow, thus increasing potential carbon storage in the valley bottom by up to 562%. Preliminary investigation into beaver restoration in Boulder County thus suggests that beaver reintroductions or beaver dam analogs are viable at multiple sites and could have a significant ecologic, hydrologic, and geomorphic effect on valley bottoms.
Recommendations for Restoration
Based on preliminary analysis and modeling, the best sites for further consideration of beaver-related restoration on Boulder County Parks & Open Space land are Delonde Creek at Caribou Ranch Open Space and Sherwood Creek at Mud Lake Open Space. At both sites, historic beaver activity is evident and suitable vegetation is abundant. Additionally, dam building is unlikely to cause damage to major infrastructure. However, grazing of aspens and willows by elk and moose at these sites could limit beaver foraging. Therefore, if beaver reintroductions are considered, grazing exclosures for moose and elk should be included in the restoration design.
Within City of Boulder Open Space and Mountain Parks land further consideration of beaver-related restoration should concentrate on South Boulder Creek from Marshall Road to South Boulder Road and Coal Creek in the Tracy-Collins and Greenbelt Plateau properties. Narrow bankfull widths on South Boulder Creek upstream of Highway 36 could make beaver dam analogs (BDAs) a suitable restoration approach.