Protection forest and avalanche risk correlation in forested terrain affected by Vaia storm
Abstract ID: 3.13041 | Accepted as Talk | Talk | TBA | TBA
Martin Pederiva (1)
Natalie Piazza (2), Enrico Tomelleri (1)
(2) Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine,, Udine, Italy
Mountain forests are increasingly undergoing disturbances such as wildfires, windstorms, and insect outbreaks. These events compromise essential services, including protection against natural hazards like avalanches. This study examined the 2018 Vaia storm’s impact on forests in Trentino, Italy, focusing on the increased avalanche risk in windthrown patches of the Fassa Valley. Using RAMMS avalanche simulation tool, different management scenarios were modeled to assess their effectiveness in mitigating avalanche risk: (1) no forest cover (clear-cut equivalent), (2) intact protective forest (pre-Vaia, reference), (3) retention of windthrown deadwood (post-Vaia), and (4) complete removal of windthrown trees. Simulations for two return periods (30 and 100 years) represented frequent and extreme avalanche events. The study focused on two sites: the Lusia Forest and the Soraga Forest. These areas provided contrasting conditions in terms of windthrow extent, forest cover, and topographical features. Lusia Forest experienced widespread windthrow potentially creating new avalanche release areas, while the Soraga Forest had more localized windthrow patches within avalanche tracks, allowing for a comparative assessment of management outcomes under varying disturbance scales. The results confirmed that intact forests (Scenario 2, reference) offered the highest protection, particularly in forests within avalanche release zones. However, in areas with historical avalanche paths, the protective role of forests was limited during extreme avalanche events. Retaining deadwood (Scenario 3) effectively reduced avalanche velocity and pressure by increasing surface roughness, whereas complete tree removal (Scenario 4) intensified avalanche impacts on exposed infrastructure. Our results underscore the need for site-specific management that considers forest cover, topography, and avalanche dynamics. In Lusia Forest, deadwood retention significantly reduced avalanche impacts on larger windthrown areas, while in the Soraga Forest, where windthrow was limited, the protective effect of deadwood was less pronounced. Furthermore, coarse woody debris in transition zones may increase the wood load making the avalanche more destructive. These findings highlight careful post-disturbance management of windthrow areas, stressing the advantages of less intervention. However, while deadwood provides protection for some time, long-term resilience depends on successful forest regeneration.
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