Using Computational Model — ADH to Evaluate Relationship of Water Surface Elevation to Wing Dikes

The use of hydraulic structures, such as wing dikes, to control flow, increase the channel capacity to carry sediment, and reduce periodic dredging requirements is an important management tool utilized on the Upper Mississippi River. Wing dikes concentrate flow in the navigation channel, control flow into secondary channels, and influence the location of channel erosion and sedimentation. This study modeled the lower portion of Pool 22 of the Mississippi River from river mile 301.2 to 304.2 using the ADaptive Hydraulics (ADH) Modeling System. Alternatives, including no dikes and dikes in the main channel, were compared to evaluate the relationship of water surface elevation to wing dikes for a range of flow conditions. This study showed that (1) construction of new wing dikes initially alters the water surface elevation, but the change is small; (2) for flow discharges less than 160,000 cfs, with decreasing the river flow, the change of water surface elevation due to wing dikes decreases; and (3) for flow discharges greater than 160,000 cfs, with increasing the river flow, the change of water surface elevation due to wing dikes decreases.