Influence of unpaved access roads on surface runoff, Sediment loss and Soil water movement within forest plantations.

Background Forestry access roads are an integral component of the infrastructure needed to carry out the core functions of managing a commercial plantation. Compared to surrounding undisturbed forested land roads forestry roads are hydrologically active areas as they are compact and frequently denuded of vegetation. Road networks have frequently been cited as the leading cause of sedimentation to water courses and therefore forestry managers must continually strike a balance between limiting off-site damage caused by roads and preserving the functionality of the road network. This project concerns itself with unpaved forestry roads as the general perception is that these roads are highly vulnerable to accelerated soil loss and contribute substantially to the sedimentation of water courses. Although several studies have been presented in the literature on the impact of unpaved forestry roads on soil and water resources a large percentage of these have been conducted outside South Africa, particularly the Eastern United States and Australia. The principles and mechanism of accelerated soil loss and runoff production from forestry access roads developed in these studies are universal but the challenge remains in adopting these results to our local context given the differences in climate and geography. Furthermore, studies on forestry access roads have been often been conducted using rainfall simulators which deliver high intensity simulated rain over a small area over a short period. Local data regarding soil loss from unpaved roads (even that external to forestry) under natural rainfall is incredibly sparse and upscaling of rainfall simulation studies to larger areas and different climates frequently meet with challenges due to the absence of corroborative information against which to gauge the predictions. As the forestry industry in South Africa increases its commitment towards self regulation and governance it becomes increasingly important that reliable and realistic estimates of surface runoff generation, erosion and transport of sediment from forestry access roads are available. This is the first and necessary step in the development of sound road management programmes and defensible policies, and forms the basis upon which this study was realized. 2.