20th Century Recovery of Beaver Dams, Floodplain Connectivity and Wetland Habitat in Connecticut Streams: Lessons for Stream Restoration
Abstract
Habitat degradation, valley incision, channelization and damming throughout the last 400 years have diminished healthy stream ecosystems. Although the eradication of the North American Beaver beginning in the 1600s greatly contributed to this degradation, leading to destruction of dams, loss of wetland habitat, ditching, and agriculture for 400 years, many upland streams in northeastern US have experienced the reestablishment of beavers beginning in the early 20th century.
There is much to be gained from studying the history of river valleys that experienced this evolution, and the natural way these streams have recovered and restored...particularly because beavers increase stream heterogeneity by building dams, creating thermal refugia for juvenile fish, decreasing erosion, providing long term carbon storage, and increasing groundwater exchange, all features that parallel the goals of restoration projects. In this study, we analyze beaver habitat modifications through aerial imagery and ground penetrating radar (GPR) in two Connecticut streams: Branch 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. We identified and mapped beaver ponds from 1934 to 2016 based on characteristic geomorphology up and downstream of a dam including open water and floodplain width. Both sites are void of beaver in 1934, exhibiting a single stream channel with little to no heterogeneity. 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. Coupling this spatial analysis with GPR enables for better understanding of historical sedimentation and paleochannel interpretation. The wetted perimeter today is more than tenfold the surface area of the paleochannel vastly improving hyporheic exchange and creating a heterogeneous stream corridor. Overall, the improved ecosystem health since beaver reestablishment demonstrates the merits of beaver habitat and other woody debris-based restoration applications.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMEP044..03F
- Keywords:
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- 1803 Anthropogenic effects;
- HYDROLOGY;
- 1820 Floodplain dynamics;
- HYDROLOGY;
- 1825 Geomorphology: fluvial;
- HYDROLOGY;
- 1879 Watershed;
- HYDROLOGY