Small dam removal as a tool for climate change resilience

Across the United States, millions of small dams fragment the landscape and alter stream ecosystems. Dam removal is increasingly used as a strategy to remove obsolete structures and to mitigate negative impacts to humans and ecosystems. The northeast and northcentral US have the highest density of small dams, along with the most active removal programs. The increasing pace and scope of dam removal projects, coupled with uncertainties surrounding climate change impacts on rivers, suggest that management agencies will be faced with decisions about the prioritization and funding of restoration projects in the context of a changing climate.

Climate change is expected to alter flow regimes, shifting peak flows to earlier in the water year and increasing the magnitude and frequency of storm events, while also contributing to seasonal droughts. Stream temperatures are expected to increase with climate change, and heat-sensitive taxa, such as brook trout, may be at risk of local extirpation.

Small dams are likely magnifying these climate impacts by exacerbating stream warming, reducing access and availability of coldwater refugia, and increasing the risk of catastrophic flooding due to dam failure. Dam removal may increase the ecological resilience of stream ecosystems by facilitating faster recovery of biota from climate-induced disturbances. Additionally, reducing public safety risks to local communities and increasing economic benefits through dam removal projects may increase community resilience to climate change.

The overarching goal of this research is to understand and quantify the multiple dimensions of dam removal in the context of climate change, while facilitating stakeholder-driven research and filling knowledge gaps. We will conduct surveys of resource managers and restoration practitioners to understand current dam removal strategies and the extent to which climate change predictions are incorporated into such projects. Socio-economic metrics of resilience will also be compiled and synthesized to help managers and decision makers value dam removal efforts in a broader context of climate adaptation.

This project is part of a larger study that will assess response of water quality (temperature and dissolved oxygen), benthic macroinvertebrates, and fishes to dam removal at >12 sites to quantify variation in responses across the Massachusetts landscape. These data will be coupled with survey results and resiliency metrics to highlight the vulnerability of a watersheds to climate change impacts, identify current actions taken to prepare for climate change, and quantify additional socio-economic benefits of dam removal. The results of this work may encourage decision makers to consider climate change resilience as an explicit objective for future projects.