Best Management Practices and Cumulative Effects from Sedimentation in the South Fork Salmon River: An Idaho Case Study

Abstract

Poor land use, including intensive unregulated logging from 1940 through the mid-1960s, contributed to massive cumulative effects from sedimentation in Idaho’s South Fork Salmon River (SFSR) by 1965. Severe damage to valuable salmon and steelhead habitat resulted. The BOISED sediment yield prediction model was used to evaluate the effects of historical and alternative land management on Dollar Creek, a representative 46.1 km² tributary watershed in the SFSR basin. Present-day management practices, properly implemented, have the potential of reducing sediment yields by about 45 to 95% compared with yields caused by the historical land use in Dollar Creek. Cumulative effects analysis is a useful tool for evaluating management alternatives. Some increases in sedimentation are unavoidable even using the most cautious logging and roading methods. However, much of the sedimentation in the SFSR and other drainages could have been avoided if logging and road construction had followed current best management practices.