River Bank Erosion in the Minnesota River Valley

Abstract

Sediments remain one of the major causes of water quality impairments in the United States. Although soil erosion from agricultural lands has been viewed as the major source of sediment to rivers and lakes, in many watersheds, river banks are also contributing a significant amount of sediments to surface waters. Currently, limited research has been reported on the methods to quantify and to understand the causes and mechanisms that control river bank erosion. The research reported in this dissertation utilized emerging technologies and novel procedures to investigate (1) historic and modern rates of river bank erosion in the Blue Earth River Basin, a major source of sediment to the Minnesota River and Lake Pepin; (2) methods to delineate seeps (a major mechanism of bank sloughing) on the face of river banks and their impact on bank erosion; and (3) water retention capacity of depressional areas across the prairie pot hole regions of the Greater Blue Earth River Basin. The results of this research indicate that river bank erosion is and has been a major source of sediment in the Greater Blue Earth River Basin even before European immigrants began to settle in Minnesota; the return intensity from light detection and ranging (Lidar) can be used to delineate seepage areas on river banks and this along with lidar generated digital elevation model provides an opportunity to quantify seepage impacts on bank erosion; and the historic storage capacity of a prairie pothole landscape such as the Greater Blue Earth River Basin is relatively small (152 mm) and concentrated only in large depressions. This suggests that restoration of depressional areas will unlikely have a major impact on river flows without additional modifications.