Sediment is a major pollutant in many southern Minnesota streams.  Direct, lethal effects from sediment on adult fish are rarely seen, but high levels of suspended solids are associated with gill damage.   Furthermore, sediment pollution in rivers indirectly affects aquatic life through decreased food supply, destruction of habitat, and decreased reproductive success.  This study identified possible mechanisms of erosion and mass wasting from river banks.  Photographs taken over a 35 mile stretch of the Blue Earth and Le Sueur Rivers in spring 2006 showed that mechanisms include creep and earthflow, mudflow, slides and slumps, undercutting, seepage, and runoff.  An experiment on the bank of the Le Sueur River further evaluated the possible link between lateral flow (ground water) and the bank erosion.  The experiment involved water addition to the upper surface of the bank and then monitoring the vertical and horizontal movement of water with a nest of tensiometers and piezometers.  Rapid bank failure occurred when there was an increase in pore water pressure as a result of an impeding layer at 2.1 m depth. Presence of a sandy layer below the impeding layer led to the development of piping effect, which is postulated as a precursor to the development of gullies on river banks. We also used the county well index data from the Minnesota Geological Survey to map possible impeding soil layers in the Blue Earth and Le Sueur River watersheds that may be forcing horizontal water flow to the river thus leading to bank failure.