Insights on New England landscape evolution from lake sediments

Humans have been argued to be the most important geomorphic agent currently acting on the planet. Motivated by these global-scale studies, over the past decade plus my research group has investigated the effects of land-use and climate change on the landscape of the northeastern United States. We have quantified legacy sedimentation in valley bottoms associated with Colonial-era land clearing and dam construction. We have also investigated how dam removal and reforestation are influencing processes. In this talk, I will present studies of sedimentation in both natural lakes and historical milldams. Sediment cores from Little Kennebago Lake in northeastern Maine record >1,200 years of sedimentation, allowing comparison of prehistoric and anthropogenic conditions. Cores collected before and after a highly erosive, localized extreme rainfall event in July 2018 provide a template for interpreting clastic event deposits found earlier in the record. I compare the Little Kennebago Lake to similar records from natural lakes around New England, which suggest differing responses to climate and land-use changes.

Further, I explore how dam construction, sedimentation, and removal at a site on the Souhegan River in southern New Hampshire has led to the creation of landforms that are a record of past land-use conditions in the watershed. This case is compared with legacy sedimentation elsewhere in the world.