INVESTIGATING 20TH CENTURY BEAVER RECOVERY AND FLUVIAL CHANGES IN CONNECTICUT UPLAND RIVERS

During the Holocene river corridors of New England, and most of North America, were inundated with the North American Beaver, Castor canadensis. Beavers shape the streams they inhabit through dam building, and in turn, vastly increase lateral connectivity and river heterogeneity. Beavers were extirpated throughout New England by the end of the 1600s (trapped for their fur, a valuable fashion commodity at the time in Europe) leading to streams without beavers, which in combination with deforestation and urbanization over the next several hundred years led to single threaded, homogenous streams. Beavers were reintroduced by wildlife managers in the 1900s and have begun to reoccupy much of their former range, albeit in far less density. In this study, we track beaver habitat formation and longevity through historical imagery and Lidar analysis coupled with Ground Penetrating Radar (GPR) surveys to identify sediment thicknesses associated with 20^th century beaver inundation. We look specifically at Carse Brook, a knickpoint tributary of the Housatonic River in Northwest Connecticut, with a well-documented history of the return of beavers and consistent dam building and maintaining over the last 30 plus years. Results show a tenfold increase in wetted perimeter following beaver reestablishment as well as fine grained sediment storage of over 1 m across the paleochannel and adjacent floodplains. Understanding the transition dynamics of single threaded fluvial to multithreaded beaver pond spotted corridors can be used as a template for how to further develop and implement restoration measures with better accuracy and effectiveness. Furthermore, estimates of dam sediment retention over time provide a sense of how these structures behave and produce habitat in their transition from solely fluvial, to fluvial, wetland and lacustrine environments.