Wednesday, November 15, 2006 - 8:00 AM

Amelioration of Bank Erosion: Some Lessons Learned from the Upper Midwest.

Stanley W. Trimble, UCLA, 1255 Bunche Hall Mail Code 52403, Department of Geography, Los Angles, CA 90095-1361

While bank erosion in the upper Mississippi River Hill Country has been greatly curtailed, it is still a problem. One factor in this curtailment has been the amelioration of stormflows, largely because of improved land use over the past 70 years. However, this condition also reduces stream sediment loads which leaves a stream “hungry’ for sediment and thus prone to erode accessible beds and banks. Fish structures have a minor but statistically significant effect in reducing channel erosion while beveling the bank and treating with rip-rap appears to completely stop erosion. But one question not answered is whether curtailing severe bank erosion in one reach can destabilize a downstream reach with “hungry” water.  Bio-treatment with willows and other trees may work in the short run but have negative effects in the long run when senile trees can destabilize streams. An important factor in the decision to treat bank erosion is whether the opposite point bar is built up the level of the cut bank—is there net loss?