In recent years, land managers, restoration practitioners, and government agencies increasingly have been employing beaver-based restoration techniques in rivers and streams, including reintroduction of beaver populations and construction of beaver dam analogues (BDAs). Beaver-based restoration has the potential beneficial effects of increasing geomorphic heterogeneity, increasing riparian vegetation biomass, storing water on the landscape, creating habitat for biota, and storing fine sediment and associated pollutants, nutrients, and organic carbon (OC). However, the rates sediment and OC accrual within beaver ponds are not adequately quantified. We conducted sediment surveys and radiometric dating of sediment cores within beaver ponds in the southern Rocky Mountains of Colorado at Manitou Experimental Forest and Coal Creek near Crested Butte. Sediment samples and cores were analyzed for OC content (%) and converted to total OC stock per area. Using a time-series of historical aerial imagery coupled with 7Be:210Pb radionuclide dating, we calculated sedimentation and carbon accretion rates. One of our study locations, Trout Creek, is an incised stream impacts by flow regulation and cattle grazing. We compare rates of sediment accumulation in beaver ponds to the amount of sedimentation that would be required to reconnect the channel to the abandoned floodplain in this system. Our study aims to provide insight into the rates at which beaver-based restoration can address human-caused stream incision. Understanding these processes on a variety of timescales, including both short-term (1-10 year) and multidecade (10-100 year), will aid river management decisions.
Graduate Student Geography, CU Boulder