Beaver dam failure in Breakneck Brook Watershed following an intense precipitation event

Harkness, Joshua; Dutton, Lily; Hall, Sarah

From the abstract: "On July 21, 2021, an intense precipitation event caused the failure of a beaver dam in the Breakneck Brook watershed on Mount Desert Island, Maine. The corresponding flood excavated a new incised stream channel, uprooted vegetation, and removed and transported rocks and soil to the wetland below. A stretch of the Breakneck Road, a popular hiking trail in Acadia National Park, was buried in 1-2 meters of sediment and other debris. With intense precipitation events forecasted to increase in frequency and intensity in the coastal Maine landscape due to climate change, similar future flood events are likely. To document this event, we mapped the flood extent, flood depth indicators, directional flow indicators, and height of damage to trees caused by the debris flow. We measured topographic transects across the newly incised channel and collected preliminary data on vegetation response to the newly disturbed site across two plant transects. By consolidating our mapping efforts into a GIS we can visualize impacts of a flood event related to an intense precipitation event in this post-glacial beaver inhabited landscape. Beyond flooding related to beaver dam ruptures, our mapping efforts reveal locations of focused erosion related to undersized and poorly maintained culverts in the watershed. Our work has led us to asking the following questions: what factors contributed to the failure of the Breakneck Brook beaver dam? How can we use this information to identify other beaver dams at risk of failure, and what threats they might pose to downstream human infrastructure and safety?"