Interstorm surface preparation and sediment detachment by vehicle traffic on unpaved mountain roads

Road survey and field rainfall simulation experiments have shown that the e rodibility of a road surface is dynamic. In the absence of extreme runoff e vents, dynamic erodibility results from the generation and removal of easil y entrained surface material by human road surface maintenance activities, vehicular detachment and overland flow events. Maintenance activities intro duce easily transportable material to the road surface where it can be entr ained by overland flow. Traffic in dry conditions detaches material that is quickly removed during subsequent overland flow events. The pre-storm erod ibility of a road is therefore largely a function of maintenance and vehicl e activity since the last overland flow event. During rainstorms, vehicle p asses increase sediment production by detaching/redistributing surface mate rial and creating efficient overland flow pathways for sediment transport. However, if incision of tracks by overland flow does not occur, post-pass s ediment transport quickly returns to pre-pass rates. Field rainfall simulat ion data suggest that sediment transport resulting from during-storm vehicl e passes is greatly influenced by the presence of existing loose material, which again is a function of prior road usage and maintenance activities. I ncorporation of vehicular effects into physically based road erosion models may be possible by parameterizing both during-storm and inter-storm change s in the supply of loose surface material as changes in surface erodibility . Copyright (C) 2001 John Wiley & Sons, Ltd.