PRELIMINARY ANALYSIS OF DAM REMOVAL IMPACTS ON THE MIDDLE REACH OF THE CUYAHOGA RIVER, OHIO

The 12 ft. (3.66 m) high Munroe Falls Dam located on the middle reach of the Cuyahoga River was completely removed in October 2005. Original plans called for lowering the dam from 12 to 6 ft. but a last minute decision was made to completely remove the dam. An earlier study conducted prior to dam removal, assessed the impact of the dam pool on channel characteristics and predicted changes that would occur after the dam was lowered. That study's predictions were based on a new dam height of 6 ft. The purpose of the study presented here is to investigate the conditions of the river now that the dam has been completely removed, compare them to the previous conditions, explain why they are changing, and predict what the future channel characteristics might be as the river adjusts to the new base level.

The removing of the 12 ft. dam has left behind extensive mud flats susceptible to slumping, the formation of rills, and other erosional features. In addition, the river channel is about 1/3 the width of the former dam pool and incipient point bars and cutbanks are being established. Three channel transects, varying in distance upstream along the dam pool, were surveyed both before and after dam removal. All three profile locations revealed slight downcutting in the north side of the channel since dam removal. Within the former dam pool, lateral erosion including scarps as well as depositional bar forms are now being established as the river adjusts to the new channel. In addition to profiling, numerous sediment samples were collected for a distance of 3 miles upstream of the dam site both before and after dam removal. Following removal, the gradient has increased and the channel width has decreased resulting in increased stream velocity. Muddy sand characterized the channel bed upstream of the dam prior to dam removal. Owing to increased stream velocity since dam removal that channel bed is now characterized by coarse sand with some gravel. This study is continuing to survey geomorphic and sedimentologic changes as the river continues to equilibrate to its new base level.