This study focused on the erosion processes in scars inflicted by storm Vivian. The windthrow study sites of Pfafers, Schwanden and Disentis were investigated in relation to the soil characteristics and the plot treatments "uncleared", "cleared", "planted" (SCHONENBERGER this issue). Thirty-five erosion scars (ES) were selected in 1992, and erosion activity was assessed by measuring the changes in their surface areas between 1992 and 2000. Furthermore, soil samples were taken to establish the grain size distribution. From a geotechnical point of view, the erodibility of the soil material increases between that in Disentis and Schwanden and that in Pfafers. Nevertheless, on the "cleared" as well as the "planted" treatments at Pfafers, the soil material proved better for vegetation re-establishment than on the same treatments in Schwanden and Disentis. During the investigation period (1992-2000) eight new ES developed, indicating that the soil stability of the study sites had entered the delicate phase when the contribution of the rotting roots of the old stand to soil stability has fallen below a critical point and the new vegetation has not yet developed enough to compensate for this loss of stability. A slight tendency towards a positive correlation between erodibility and inclination was found. The key factors controlling the re-establishment of vegetation cover on ES were deduced to be the soil material, followed by the inclination and the different treatments. In addition, it can be concluded that careful selection of the wood harvesting method and its appropriate application will help prevent the development of erosion scars.