Sediment mobility and bed armoring in the St Clair River: insights from hydrodynamic modeling |
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| Authors: | Xiaofeng Liu Gary Parker Jonathan A Czuba Kevin Oberg Jose M Mier James L Best Daniel R Parsons Peter Ashmore Bommanna G Krishnappan Marcelo H Garcia |
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| Institution: | 1. Department of Civil and Environmental Engineering, University of Texas at San Antonio, , San Antonio, TX, USA;2. Ven Te Chow Hydrosystems Laboratory, Department of Civil and Environmental Engineering, University of Illinois at Urbana‐Champaign, , Urbana, IL, USA;3. Departments of Geology, Geography, and Mechanical Science and Engineering, University of Illinois at Urbana‐Champaign, , Urbana, IL, USA;4. US Geological Survey, Office of Surface Water, , Urbana, IL, USA;5. US Geological Survey, , Tacoma, WA, USA;6. School of Earth and Environment, University of Leeds, , Leeds, UK;7. Department of Geography, University of Western Ontario, , London, Ontario, Canada;8. Aquatic Ecosystem Impacts Research Branch, National Water Research Institute, Canada Centre for Inland Waters, , Burlington, ON, Canada |
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| Abstract: | The lake levels in Lake Michigan‐Huron have recently fallen to near historical lows, as has the elevation difference between Lake Michigan‐Huron compared to Lake Erie. This decline in lake levels has the potential to cause detrimental impacts on the lake ecosystems, together with social and economic impacts on communities in the entire Great Lakes region. Results from past work suggest that morphological changes in the St Clair River, which is the only natural outlet for Lake Michigan‐Huron, could be an appreciable factor in the recent trends of lake level decline. A key research question is whether bed erosion within the river has caused an increase in water conveyance, therefore, contributed to the falling lake level. In this paper, a numerical modeling approach with field data is used to investigate the possibility of sediment movement in the St Clair River and assess the likelihood of morphological change under the current flow regime. A two‐dimensional numerical model was used to study flow structure, bed shear stress, and sediment mobility/armoring over a range of flow discharges. Boundary conditions for the numerical model were provided by detailed field measurements that included high‐resolution bathymetry and three‐dimensional flow velocities. The results indicate that, without considering other effects, under the current range of flow conditions, the shear stresses produced by the river flow are too low to transport most of the coarse bed sediment within the reach and are too low to cause substantial bed erosion or bed scour. However, the detailed maps of the bed show mobile bedforms in the upper St Clair River that are indicative of sediment transport. Relatively high shear stresses near a constriction at the upstream end of the river and at channel bends could cause local scour and deposition. Ship‐induced propeller wake erosion also is a likely cause of sediment movement in the entire reach. Other factors that may promote sediment movement, such as ice cover and dredging in the lower river, require further investigation. Copyright © 2012 John Wiley & Sons, Ltd. |
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| Keywords: | St Clair River numerical model field measurement gravel bed sediment transport armoring till erosion morphology bathymetry |
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