Sediment-yield data for 121 sites in eastern Montana have been compiled from results of studies conducted by various Federal, State, and private agencies. Methods used to determine mean annual sediment yields included reservoir sedimentation surveys, suspended-sediment sampling in streams, and estimates of gross erosion and indirect estimation based on physical characteristics of the basin. Multiple-regression equations were developed and evaluated for their adequacy in estimating mean annual sediment yields from small, ungaged watersheds in eastern Montana. Sediment yields determined from reservoir surveys were used as the dependent variable because they were considered the most representative of long-term yields. Independent variables consisted of basin characteristics which could be measured from maps or obtained from published sources. Consequently, equations developed in this study do not require onsite data. Evaluation of equations indicated that the best prediction capability was obtained when reservoir basins were segregated into classes of similar vegetation/soil complex. The predictive capability of regression equations developed for each of three classes of vegetation/soil complex, as indicated by the coefficient of determination (R2), ranged from 0.59 to 0.96. Corresponding standard errors ranged from 95 to 20 percent. The equations are applicable for small drainage basins of 2 square miles or less within the study area. (USGS)
