River Bank Erosion Assessment using 3D Hydrodynamic and Sediment Transport Modeling
River bank erosion is one of the most damaging forms of water erosion. It causes loss of agricultural lands, recreational and industrial sites, and damaged hydraulic structures and infrastructure. It is also a major source of sediments entering river channels. A number of factors affect the rate of river bank erosion, including topography, climate, channel geometry, soil properties, type of vegetation, and human-induced changes to the fluvial system and land use.
An effective tool in controlling river bank erosion is the planning and installation of erosion control practices. Both structural and vegetative practices and their combinations are applied to river bank stabilization. These practices are aimed at reducing flow velocity, increasing shear stress of the soil, and armoring the affected river bank sections.
This chapter describes the application of the three-dimensional (3D) model ECOMSED to the design of river bank protection at a site in Ohio. ECOMSED is a hydrodynamic and sediment transport model designed to simulate time-dependent distributions of water levels, temperature, salinity, tracers, and cohesive and non-cohesive sediments in marine and freshwater systems. The model was chosen because of its capabilities to simulate 3D river flow and sediment transport through complex channel sections containing flow diversions and constrictions.
Five scenarios of different river hydraulic conditions at the study site were simulated by the model. For each scenario, the model provided high-resolution outputs of hydraulic parameters and sediment transport characteristics required for the river bank protection design. The outputs were plotted in GIS, and the locations most prone to bank erosion were identified. These locations were then compared to the locations of eroded river banks observed during a site visit.
The results showed that the model correctly identified river sections already affected by bank erosion. In addition, the model predicted another location where bank erosion is expected to develop in the near future. The erosion rates in the affected sections were found to depend on river flow conditions. The model indicated that due to the complex hydraulic conditions in the study section, some locations are more susceptible to erosion during lower river flow conditions than during certain high river flow conditions. The results were used to select and design river bank protection most appropriate for the site.
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