Project Number:
Start Date: 2026-01-29 End Date: 2027-01-28
Principle Investigators:
David Burdick (Research Associate Professor)
James G. McKown (Research Scientist)
Abstract:
Over the past thirty years, almost fifty small dams (< 15 ft height) have been removed from New Hampshire’s landscape out of the nearly 4000 registered with the state Dam Bureau. In the Seacoast region several head-of-tide dams with upstream reservoirs have been or are proposed for removal including the Great Dam in Exeter (2016), Sawyer Mills Dams in Dover (2019-20), and Mill Pond Dam in Durham (2025 – 26). One of the main concerns with dam removal is the rate and overall development of the floodplain wetland in the former reservoirs including colonization by invasives and other changes in vegetation community. Our understanding of vegetation change after dam removals have been limited to either case studies of large dams (> 100 ft), short monitoring periods (1 – 2 years post-restoration), or lack of pre-restoration monitoring. Dewatering of the impoundments behind the Great Dam and Sawyer Mill Dams provides a rare opportunity to assess the development of the vegetation community, floodplain geomorphology, and hydrology after 5 – 9 years when the systems are expected to have stabilized. The hydrology will be assessed with installed water level recorders and salinity probes down and upstream of the dams. Vegetation and geomorphology will be evaluated with transect – plot monitoring along the length of the former reservoirs. The first set of proposal objectives are to characterize the vegetation community and floodplain geomorphology to inform future small dam removal projects in New Hampshire. Mill Pond Dam provides an opportunity to document pre-restoration conditions of the vegetation community. Overall, the proposal is designed to instruct and guide restoration expectations of future small dam removal projects in the State of New Hampshire through comprehensive monitoring of biological (plant communities), hydrologic (water and salinity levels), and geomorphic metrics (profiles).
