The purpose of this study is to evaluate the streambank erosion at four sites on the Minnesota and LeSueur Rivers and use field data to prepare proposals for stabilization of the banks. The expectation is that the solution will consist of submerged vanes placed according to design guidelines established at the Iowa Institute of Hydraulic Research.
Submerged vanes are small flow training structures designed to modify the nearbed flow pattern and redistribute the flow and sediment transport within the channel cross section. The structures are installed at an angle of 15° to 30° with the flow and their initial height is 0.2 to 0.4 times the flow depth at design stage. The vanes function by generating a secondary circulation in the flow. The circulation alters the magnitude and direction of the bed shear stresses and causes a change in the distribution of velocity, depth, and sediment transport. As a result, the bed aggrades in one portion of the channel cross section and degrades in another. In river bends, the vanes are laid out to move sediment toward the outer bank to stabilize the toe of the bank and prevent the bank from being undermined. Along highly erodible banks, the vane system should be supplemented with a "blanket" of rocks (12 to 18 inches) on the bed and lower bank between the innermost array of vanes and the bank.
During a field trip on October 29-30, 1992, it was determined that only three sites should be considered for this solution. The sites were TH 169 on the Minnesota River, and TH 22 and TH 66 on the LeSueur River.
