Technical Abstract: Livestock grazing of riparian areas can have a major impact on stream banks and stream integrity if improperly managed. The goals of this study were to determine the sediment and phosphorus (P) losses from stream bank soils under varying cattle stocking rates and to identify additional factors that impact stream bank erosion in the Southern Iowa Drift Plain. The research was conducted on thirteen cooperating beef cow-calf farms within the Rathbun Lake watershed in South Central Iowa. Stream bank erosion rates during three years were estimated by using an erosion pin method. Eroded stream bank lengths and area, soil bulk density and, total P (TP) concentrations in stream bank soil were measured to calculate soil and TP lost via stream bank erosion. The length of severely eroded stream banks and soil compaction of the riparian areas of the pastures were positively related to an increase in stocking rates of grazing livestock on the pasture stream reaches. While there was no direct relationship between bank erosion and stocking rate, the erosion rates from two sites enrolled in the Conservation Reserve Program (CRP) were significantly lower than those from all grazed pasture sites, especially when seasonal effects, specifically winter/spring, were considered. These results suggest that use of riparian areas as pasture may negatively impact water quality and channel integrity through increased sediment and P losses from bank erosion, and that the impact could be reduced through management of livestock stocking densities within these riparian areas.