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Optimizing and Implementing Floating Wetland Breakwaters to Reduce Shoreline Erosion in Reservoirs
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Soil Erosion Research Under a Changing Climate, January 8-13, 2023, Aguadilla, Puerto Rico, USA .(doi:10.13031/soil.23034)Authors: Jason R Vogel, PhD, Maxwell O’Brien, Saliou Diallo, Grant M Graves, Keith Strevett, Daniel Storm, Steven Patterson
Keywords: Floating wetland breakwater, Shoreline erosion, Wave height.
Abstract
Lake Thunderbird, which is located to the east and south of Oklahoma City, Oklahoma, is on the Army Corps of Engineers 303(d) list of impaired water bodies due to three limiting factors, one of which is turbidity. The lake has approximately 50 miles of shoreline with 83% having some degree of erosion. Over the years, shoreline erosion has resulted in significant loss of shoreline and deposition of the eroded material into the lake, effectively reducing the holding capacity of the lake and adversely affecting water quality. To reduce the erosive action of the waves, this project was completed to utilize floating wetland breakwaters (FWBs) anchored near the shoreline to reduce the energy from wave action.
The three objectives of this study were: (1) Test multiple FWB frame designs to determine the best design for maximizing wave-energy reduction; (2) Complete laboratory-scale experiments on model FWB frames to determine the viability of using scale models to predict full-scale performance; and (3) Complete field testing of the selected design to determine in-situ wave reduction and the resulting impact on shoreline erosion.
Overall, the project was successful in meeting the three project objectives. The full-scale mesocosm demonstrated that a frame design with 11 ballasts that were each 3-feet long per 10-foot section provided the most wave energy reduction per materials cost. Through the laboratory-scale experiments, we were able to utilize similitude concepts to demonstrate that, in general, we could predict full-scale wave-reduction performance using smaller scale models when similitude concepts are recognized in the design. Finally, our field implementation resulted in the best wave reduction performance of all of our tests at multiple scales, including comparisons to designs available in literature. Based on wind speed and fetch data for southerly winds and shear stress determination from the shoreline soils, we estimate that our FWB design is able to reduce 96% of the waves to heights smaller than what is required to cause detachment erosion on that bank. In addition, the materials‘ cost per foot was comparable to other shoreline erosion techniques.
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