20TH CENTURY RECOVERY OF BEAVER DAMS, FLOODPLAIN CONNECTIVITY AND WETLAND HABITAT IN CONNECTICUT STREAMS

Beaver dams create a discontinuity in fluvial systems, raising the water level behind the dam and extending laterally out of the channel and into the floodplain, forming a wetland. The northeastern US provides a natural laboratory to study the interaction between beaver dams, floodplain connectivity and wetland habitat. Many floodplains in this region can be characterized to have had widespread beaver occupation prior to European Colonization in the 1600s, followed by beaver eradication, destruction of dams, loss of wetlands, wetland ditching, and agriculture for 300-400 years, and then the reestablishment of beavers beginning in the early 20^th century. In this study, we analyze the distribution and rate of beaver habitat establishment from 1934 to 2016 in two Connecticut streams: Buell Brook, a low gradient, meandering forested stream in eastern Connecticut, and Carse Brook, a steep incised knickpoint tributary of the Housatonic River in western Connecticut. Spatial analysis was done in ArcMap with 1934, 1965, 1990, 2008 and 2016 imagery from the Connecticut Department of Energy & Environment (CTDEEP). In each year beaver ponds were identified and mapped based on characteristic geomorphology up and downstream of a dam including open water and floodplain width. Both locations are void of beaver in 1934, exhibiting a single thread, often meandering stream with little to no heterogeneity and narrow floodplains. Over the 82-year period beaver habitat expanded along both streams with densities upwards of 10 dams in less than one kilometer of river and floodplains widened to over 250m. In 2016 Carse Brook had 58 beaver dams, a substantial increase even from 1990 when there were 23 total, indicating a rapid recent expansion compared to the 1934-1990 time period. There are some differences in beaver distribution and establishment between the two sites which highlights the importance of slope, flood frequency and local land use practices when assessing beaver populations over time. This spatial analysis provides an understanding of historical significance and reestablishment patterns at two varied sites illustrating the importance of beaver and beaver habitat on natural river systems and the potential for restoration and ecosystem management applications.