Cooperative Fish and Wildlife Research Units Program:
Education, Research and Technical Assistance for Managing Our Natural Resources


Quantifying wetland change following small dam removal in Massachusetts

September 2021 - September 2024


Participating Agencies

Across the United States and within Massachusetts, the rate of dam removals pales in comparison to the number of dams aging across the landscape. Though intended to protect wetlands and waters, wetland regulations pose an obstacle to efficiently removing dams and restoring free-flowing waters. Because dam removal inherently alters the open water ecosystem as well as contiguous wetlands, those seeking to remove dams must address regulatory requirements under Sections 401 and 404 of the Clean Water Act as well as State and local wetland protection regulations. These regulatory protections do not adequately facilitate ecological restoration projects which may significantly alter existing wetland resources to improve the health of a system in the longer term. Specifically, the dearth of information on wetland response following dam removal has resulted in significant uncertainty for removal practitioners and regulators as they balance the potential ecological benefits and impacts related to dam removal.

To address this uncertainty, we aim to understand and model how wetland area changes upstream of the impoundment, within the impoundment area, and downstream of the former dam over short (0-2 years) and longer (4-6 years and 9-11 years) durations following dam removal by analyzing 26 small dam removal projects completed in Massachusetts between 2000 and 2012. Additionally, we will evaluate the effect of landscape characteristics and dam removal design on wetland change. We will achieve these objectives through aerial interpretation of aerial imagery and primary permitting data. Our results could describe and set expectations for future wetland change following dam removal, as well as identify dam removal project designs that minimize wetland conversion.