Ellen Comes Graduate Defense Seminar

Ellen Comes, MS Candidate in Ecological Restoration, will present Geomorphic Response to Lowhead Dam Removal in a Mid-sized Urban River System as her Graduate Defense Seminar in 128 Heffner Wetland Research and Education Bldg.

As lowhead dams (< 7.5 m in height, run-of-river structures) are reaching the end of their functionality, a common river restoration technique has increasingly been removal of dams to transform the previously impounded rivers to free-flowing systems. As a consequence, there is growing interest in understanding physical channel adjustment once a dam is removed since geomorphic response to dam removal has become an emerging science within the past 20 years. Specifically, this research reports on the geomorphic responses of the Olentangy and Scioto Rivers (Columbus, Ohio) following two lowhead dam removals within an urban landscape. This study used a paired control-treatment design to quantify the geomorphic response of river channel reaches (~ 450 m long) above and below a removed lowhead dam, in comparison with reaches adjacent to existing lowhead dams. My field work included collection of repeat bathymetric surveys and near-surface riverbed substrate at several time periods following dam removal, allowing for analytical comparison of erosion and deposition patterns, development and evolution of in-channel macro-features, and reach-scale metrics of heterogeneity. Results indicate an overarching trend of summer erosional and winter depositional processes with some coinciding coarsening and fining of riverbed substrate and significant changes in reach topographic heterogeneity throughout the river system. Reaches upstream of the removed lowhead dams were net erosional for the duration of the study (both < 3 years).