Effects of traffic frequency and skid trail slope on surface runoff and sediment yield

Abstract

The generation of surface runoff and sediment yield was studied on skid trails in the temperate forest of Iran. The aim of this study was to evaluate the effects of traffic frequency and skid trail slope on runoff and sediment production. Three levels of skidder passes (i.e. 3, 7 and 14), and three levels of slope (i.e. <10%, 10–20% and >20%) were studied. Thirty-six runoff plots (9 control plots and 27 sample plots) were established in the study area. The results indicated that surface runoff and sediment production was affected by traffic frequency and skid trail slope; also interaction between skidder passes and skid trail slopes was significant (p < 0.001). Surface runoff volume and sediment production was greatest at the skid trail in the 14 passes and >20% slope, and was the lowest at the skid trail with the 3 passes and <10% slope. The undisturbed area did not generate any runoff during the observation period. High correlation coefficients showed that the pre-harvest bulk density, total porosity and litter cover of the skid trail had statistically significant effects on surface runoff as well as on soil loss. Increase in runoff and soil loss with the increase of skid trail slope shows that care and surveillance are necessary during skid trail designing, to prevent reduced soil quality and, consequently, forest productivity.