Using rainfall simulation to guide planning and management of rehabilitated areas: Part II. Computer simulations using parameters from rainfall simulation

This paper reports computer simulations carried out using data from a rainf all simulator study on a steeply sloping revegetated area (a soundbund) at the NorthParkes Mine, near Parkes in New South Wales, Australia. Simulations of slope stability used a combination of daily time-step models to consider soil water balances and runoff, growth of grass/legume pasture and soil erosion. Simulations indicated that long-term erosion rates on th e soundbund would be low (1.01-1.27 t ha(-1) yr(-1)) due to low runoff rate s and good vegetative cover. The simulations highlighted that peak vegetati ve growth occurred prior to the period of peak erosion hazard, with carry-o ver dry matter being crucial for erosion control during the period of peak rainfall erosivity. This, in turn, indicated that grazing during the period s of peak growth and peak erosion hazard should be avoided (to avoid loss o f dry matter). It also indicated that there was value in establishing grass species that would give greater growth during summer months, and that may produce dry matter that is more persistent through time. Simulations of stormwater flows in channels draining various lifts on the s oundbund compared a range of alternatives with respect to channel length, g radient and roughness. The simulations indicated little effect of channel l ength on peak flow rates or depths once channel lengths exceeded 250 m and also showed little effect of vegetative roughness on peak flow rates or dep ths once Manning's n values exceeded 0.05. Implications of these results fo r design of drainage channels and drop structures on the soundbund an discu ssed. Copyright (C) 2000 John Wiley & Sons, Ltd.