The impact of off-road vehicle traffic on the gravel plains of the central Namib Desert, Namibia

Abstract

Abstract provided by author:

Microtopographical measurements - surface area and depth of track - were used to determine the physical effects of the vehicle treatments at the soil surface while penetrometer resistance, gave an indication of the sub-surface effects of vehicle damage

Cornering resulted in the highest visual impact, followed by the multiple pass track and that made by narrow lug tyres. Vehicle tracks made at high speed were less visible than those made at a lower speed and tended to recover visually at a much faster rate. The multiple-pass track resulted in the smoothest, deepest rut, while the speed track was generally shallow with a rough surface

Soil strength determinations based on penetrometer resistance revealed that multiple-pass and narrow tyre tracks resulted in subsurface soil disturbance to depths significantly greater than that resulting from the other treatments. The cornering and speed treatments resulted in the highest impact within the surface layers of soil. Generally disturbance of soil structure did not extend to depths greater than 80 mm, being, for the most part, confined to the upper 0-50 mm zone

Vehicle disturbance was found to have a highly significant effect on lichens with cover being reduced by as much as 80 percent following impact. It is suggested that this contributes significantly to the high visual impact of vehicle tracks on these surfaces. The least sensitive surfaces were the calcrete plains further from the coast, where the lowest track density was observed

The rehabilitation of vehicle tracks using handheld rakes was investigated with the intention of determining the optimal dimensions of an instrument for successful surface rehabilitation. It is suggested that further research be conducted into the design of a related instrument which can be attached behind the rear wheels of a vehicle for immediate rehabilitation

The suggestions for the reduction or prevention of vehicle impact, derived mainly from the conclusions of this study, involve education, careful planning and a certain degree of discipline in the field. Awareness of field staff to the problems associated with off-road driving was stressed