Mapping erosion risk and selecting sites for simple erosion control measures after a forest fire in Mediterranean France

Major forest fires occur periodically in the Mediterranean environment. The impact of forest fires on soil erosion and runoff processes has been studied extensively, and it has been demonstrated that the first months after a fire represent a high risk period. Erosion control strategies must be established in the weeks following a forest fire to reduce fire impacts during the critical phase. Both dead and live vegetation techniques can be used to either reduce soil loss from slopes or trap sediments in streams before they enter the main channel: these include log erosion barriers, log debris dams and grass filter strips. The major challenge is defining where to position the measures quickly in a catchment where several thousand hectares have been burned. The method proposed here is based, firstly, on a simple soil erosion model that identifies critical erosion zones, and secondly, on a more detailed analysis of high risk slopes according to their potential impact on the main river channel, the value of the soil resource to be protected, the availability of pine logs, and accessibility to the site. Measurements of suspended sediment load in the main channel and tributaries confirmed that the erosion risk map was suitable for the purposes of the study. Many of the recommendations suggested were implemented and a study is underway to evaluate their effectiveness in reducing erosion and trapping sediments.