The Cwmcarn canal reservoir was built in around 1792 to provide water for the Monmouthshire Canal's Crumlin Arm. The dam burst catastrophically on 14th July 1875, resulting in devastation of the valley below and the loss of 13 lives. The earth dam was 128m long and 10.7m high. Only the south-eastern half of the dam remains as an earthwork, cut through by the Cwm Carn river.
Source: Cadw scheduling description.
RCAHMW 05.03.2008