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Geomorphic Response to Lowhead Dam Removal in a Mid-Sized Urban River System

Comes, Ellen Louise
http://rave.ohiolink.edu/etdc/view?acc_num=osu1471617826

Abstract Details

2016, Master of Science, Ohio State University, Environment and Natural Resources.
As lowhead dams (< 7.5 m in height, run-of-river structures) are reaching the end of their functionality or structural integrity, their removal has become an increasingly popular river management and restoration practice. Geomorphic adjustment to dam removal is an emerging science; however, studies are limited that track the character of geomorphic change, particularly the short-term (intervals of only a few months) changes that occur in first few years following dam removal, which can have critical consequences on ecosystem processes occurring over these time scales. The present study reports on the geomorphic responses of the Olentangy and Scioto Rivers (Columbus, Ohio, USA) 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 and compare these responses to geomorphic behavior above and below existing lowhead dams over the same time period. Reaches upstream of removed dams included those which were passively-restored and actively-restored, which consisted of in-channel engineering activities. Geomorphic change was quantified through repeat bathymetric surveys using an acoustic Doppler current profiler (ADCP) and near-surface riverbed substrate sampling at several time periods (~ 2 surveys per year) within the 2-3 years following dam removal. The objective of this study was to characterize the nature of geomorphic response in terms of sediment transport processes, which was achieved through quantitative and qualitative comparison of erosion and deposition patterns, development and evolution of in-channel macrofeatures, such as the thalweg and pools, changes in reach-scale metrics of heterogeneity, and changes in riverbed substrate. Results indicate an overarching trend of summer erosional and winter depositional processes throughout the river system with some coinciding coarsening and fining of riverbed substrate and significant changes in reach topographic heterogeneity. Reaches upstream of the removed lowhead dams were net erosional for the duration of the study, which was likely a result of the removal of previously impounded sediments. Even though there were observed patterns of seasonal coarsening and fining, the upstream reaches had overall coarsening of riverbed substrate (by 22mm and 17 mm on the Olentangy and Scioto Rivers, respectively). The restored reaches also saw the establishment of pools and runs, with some changes in topographic heterogeneity over time. Downstream of the dam removal, the Olentangy River and Scioto Rivers were net erosional and net depositional, respectively; substrate initially fined at both reaches (by 10 and 5 mm, respectively) but coarsened for the overall study period. Macrofeatures experienced moderate adjustments attributed to sediment movement through the reach, with little change in topographic heterogeneity. The results of this study contribute to the growing body of knowledge surrounding dam removals, highlighting that observed geomorphic changes reflect in part differences in the seasonal character of streamflow and sediment regimes.
Mazeika Sullivan, PhD (Advisor)
Kristin Jaeger, PhD (Committee Member)
Kaiguang Zhao, PhD (Committee Member)
167 p.
Environmental Science; Geomorphology; Hydrology; Water Resource Management
Geomorphic Response, Lowhead Dam Removal, Mid-Sized Urban River System

Recommended Citations

Citations

  • Comes, E. L. (2016). Geomorphic Response to Lowhead Dam Removal in a Mid-Sized Urban River System [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471617826

    APA Style (7th edition)

  • Comes, Ellen. Geomorphic Response to Lowhead Dam Removal in a Mid-Sized Urban River System. 2016. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1471617826.

    MLA Style (8th edition)

  • Comes, Ellen. "Geomorphic Response to Lowhead Dam Removal in a Mid-Sized Urban River System." Master's thesis, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471617826

    Chicago Manual of Style (17th edition)

osu1471617826
288
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This open access ETD is published by The Ohio State University and OhioLINK.