Evaluating the impact of natural disturbances on protection forests: a multi-approach analysis

Mountain forests play a major role in preventing and mitigating natural mass movements such as rockfall or shallow landslides. Correct management should be aimed to maintain this protective function along with the natural evolution of forest stands as well. But what happens when natural disturbances affect stand dynamics? Assessing the effects of such disturbances on the forest cover and, therefore, assessing the residual protective function of disturbed stands is a key issue to defining priorities among the different intervention and management practices that are needed after a disturbance event. In this context, within the recent project “VaiaLand”, we are planning to evaluate the impacts of the storm Vaia, that occurred in October 2018, over the protective efficiency of some alpine stands in the province of Belluno (Veneto, Italy) towards rockfall and shallow landslides hazards. Current technologies may help provide a first rough assessment that can help evaluate the protective efficiency of damaged stands. Concerning rockfall hazard, using LiDAR data we assessed the terrain roughness caused by the presence of lying logs (height from the ground). We run rockfall simulations with RockyFor3D to observe any change in the protective efficiency of the stands in two study sites. Our results show that biological legacies act mainly as a barrier against falling blocks reducing their reaching probability and partially reducing their kinetic energy. The next step of our research will focus on shallow landslides hazard to understand and quantify, on sloped windthrown areas, the increase in susceptibility to this hazard caused by the leak of root reinforcement. To achieve such results, we will apply SOSlope and SlideforMAP models at different scales to better comprehend slope instability dynamics. This project is targeted to help to understand which management strategies are more effective for risk mitigation after natural disturbances events in an alpine scenario.