Sediment Production Model for the South Branch of the Buffalo River Watershed

To predict the relative risk of soil erosion from various parts of the South Branch Buffalo River watershed, southwest of Moorhead, MN, the surficial geology of the area has been studied and a methodology has been developed. The methodology comprises the use of the sediment production component of the United States Department of Agriculture AnnAGNPS model to quantify surface erosion rates and sediment yields from the upland areas, and a sediment routing model to estimate the channel bank migration rates and the supply of sediment from stream bank sources. The AnnAGNPS model was calibrated using the suspended sediment load observations made at Sabin, Minnesota during 1978. The calibrated model predicts a sediment yield of 14,400 tons/yr at the watershed outlet (13.0 tons/km²/yr) for the years 2002-2005. This amount is nine times larger than the channel bank erosion estimate of 1600 tons/yr (1.45 tons/km²/year). Modifications to the AnnAGNPS program allow routing multiple grain sizes of sediment produced in the watershed, including aggregated pellets formed from silts and clays, and predicting the likely locations of sediment deposition in the river network.