Volume of Snowmelt Intercepted by Logging Roads

Snowmelt runoff into two 100-ft sections of logging road near the Montana-Idaho border was measured from 1965 to 1967. For two years, subsurface seepage from the road cut was measured with overland flow deflected by sheetmetal barriers. A prediction equation was developed to predict seepage flow for one section using the observed flow in the other section. In 1967, the overland flow barriers were removed from one section and the total runoff volume-seepage flow plus overland flows was measured. The predicted daily seepage flow volumes were estimated using the developed equation, and the daily amount of overland flow was estimated as the difference between the observed total runoff and the predicted seepage flow. Of the total daily runoff, 58% was seepage flow and 42% was overland flow. The average total flow volume which entered 100 ft of logging road was 0.29 acre-ft per day and the average peak discharge rate was 0.26 cfs.