CONTINUED MONITORING OF THE EFFECTS OF TWO DAM REMOVALS ON THE MIDDLE CUYAHOGA RIVER, OHIO

Dams that no longer serve their initial intended purpose are now candidates for removal in order to improve the fluvial environments they impact. The removal of the Munroe Falls Dam and the LeFever Dam from the middle Cuyahoga River in Summit County, Ohio has provided an opportunity to quantify how rivers respond to dam removal. This research extends eleven years of monitoring by measuring river transects and sampling channel sediment in 2016. The 2013 removal of the LeFever Dam was preceded by the 2005 removal of the Munroe Falls Dam that stood 5.4 kilometers upstream of LeFever. Prior research documented rapid incision and lateral erosion in the 2.5 years following the Munroe Falls Dam removal. The 2016 survey results document that within the former Munroe Falls Dam pool the rate of lateral erosion has slowed considerably but still occurs by slumping of vertical banks of former impoundment fill. The channel is comprised of a gravel or bedrock substrate as a result of the limited sediment supply to the middle Cuyahoga River. The sediment eroded from the former Munroe Falls Dam pool accumulated in the downstream LeFever Dam pool. In the year following the LeFever Dam removal, rapid incision remobilized and transported sediment downstream to the next dam pool. The 2016 survey of the former LeFever Dam pool documents the continued erosion of sand deposits located in the lee of large woody debris. In addition, the downstream migrate of gravel bars can produce substantial geomorphic change to the channel at the local river transect scale. At the transect located closest to the former the LeFever Dam, the thalweg aggraded with sand eroded from the upstream end of the former impoundment. This continued monitoring study of the middle Cuyahoga River helps quantify the long-term response of the river to dam removal.