Abstract The 2005 removal of the 3.6-m-high Munroe Falls Dam from the middle Cuyahoga River, Ohio, provided an opportunity to assess dam removal channel-evolution models and to anticipate impacts from additional dam removals on the Cuyahoga River. Preremoval geomorphic and sedimentologic conditions were characterized. Monitoring of the river response to dam removal has continued for 5 yr. The dam removal lowered base level and increased flow velocity upstream of the former dam site. Postremoval, the initial channel response was rapid incision to the predam substrate, followed by rapid lateral erosion of the exposed impoundment fill. Four to nine months after removal, dewatering and vegetation of the exposed impoundment fill greatly reduced the rate of lateral erosion. For 2.5 yr post -removal, sandy bar forms were present upstream of the former dam, and sand was transported under all flow conditions of the year. Subsequently, the bed has become armored with gravel. Downstream of the former dam site, the channel aggraded with sand, causing flow to occupy meander bend chutes that had formerly only been active during high flow. A sandy deltaic feature has accumulated 3.3 km downstream in the impoundment created by the Le Fever Dam. The impacts of the Munroe Falls Dam removal are generally well described by published channel-evolution models with minor exceptions due to local geology and hydrology. The similarities between the Munroe Falls and Le Fever Dam impoundments suggest that this study can aid in understanding the impacts of the possible future removal of the Le Fever Dam.

Abstract Dams on rivers modify habitat and water chemistry, resulting in degradation of fish and macroinvertebrate community integrity within and, in some cases, downstream of the dam pools. Thus, removal of a dam is usually accompanied by the expectation of improved habitat quality and biotic integrity. The Ohio Environmental Protection Agency applies a Qualitative Habitat Evaluation Index, an Index of Biotic Integrity (IBI, fishes), and an Invertebrate Community Index (ICI) to assess stream habitat quality and the habitat-dependent structural and functional integrity of the fish and invertebrate communities. Our objective was to demonstrate that these three indices reliably detect differences in the quality of habitat and fish and macroinvertebrate communities between dam pools and free-flowing reaches and that they are sensitive to changes in habitat and biotic condition following dam removal. Data from 21 stream reaches in Ohio containing dams showed that habitat and biota in dam pools possess lower quality than nearby upstream and downstream reaches. Case studies of dam removals on the Cuyahoga, Olentangy, and Sandusky Rivers confirmed that the indices are sensitive to the rapid changes in habitat and biotic communities that accompany return of dam pools to free-flowing conditions. IBI and ICI scores indicated that the former dam pools had met or exceeded the designated aquatic life use criteria within 1 yr following dam removal. We conclude that the IBI and ICI are valuable tools for measuring the rapidity and extent of changes in the fish and macroinvertebrate communities, respectively, following dam removal.