What caused the avulsion of the Suncook River in Epsom, New Hampshire (15-16 May 2006)?
Avulsions are common geologic processes on deltas, alluvial fans, and floodplains but are rare outside of these settings. Some of the largest losses of human life in recorded history have been due to avulsions. Nonetheless, their causes remain incompletely understood. The Suncook River did not avulse in one of the aforementioned settings. Rather, the avulsion occurred outside of the 100-year floodplain, crossed a small wetland, and incised a low glacial ridge. The avulsion created a new channel 0.7 km long, abandoned 3.2 km of former channel, and eroded an estimated 115,000 cubic meters of sediment. As a result of the avulsion, 298 homes downstream are currently at greater risk of flooding and 63 acres of farmland, prime habitat for trout and brook mussels, and use of a sand quarry were lost. Bridge stability has also potentially been affected. This study, in collaboration with Mariela Perignon (graduate student, MIT) and Will Ouimet (Penn State), is designed to determine the nature an
