Erosion Processes on Arid Minespoil Slopes

Surface wash and dry ravel erosion rates from minespoil were measured for 4.7 yr after initial reclamation at a site in western Nevada. Average annual total erosion from all 15 plots ranged from 0.48 to 1.10 Mg ha−1. Neither mulching treatment nor slope gradient (3:1 vs. 2:1) significantly affected surface wash from reclaimed minespoils. About 70% of the total wash load from the entire study period occurred during two midsummer to autumn periods (1989 and 1990) in which the most intense storms occurred. Southwest‐facing slopes (windward) had significantly higher surface erosion compared with northeast‐facing slopes (leeward). The higher surface roughness encountered on 2:1 slopes appeared to more effectively control surface wash than gentler (3:1) slope gradients or early‐stage vegetative cover. Straw mulch significantly reduced ravel erosion from the relatively smooth 3:1 slopes. Mulch treatment was not effective in reducing ravel erosion from rougher, 2:1 slopes. Windward (southwest‐facing) slopes had significantly higher ravel erosion than northeast‐facing slopes. Ravel rates were not as directly affected by rainfall intensity as were surface wash rates. Regressions of surface wash with EI (rainfall energy‐intensity factor) were best with short‐term intensities (i.e., EI5, R2 = 0.94); regressions of ravel with EI were best using longer term intensities (EI30; R2 = 0.83). Except for very dry collection periods (including autumn to spring), surface wash exceeded ravel.