Abstract ID: 3.11203 | Accepted as Talk | Talk/Oral | TBA | TBA

Large, infrequent disturbances (LIDs), such as storms, wildfires, and volcanic eruptions, can disrupt entire mountain catchments, yet their secondary or cascading effects are often overlooked. A deeper understanding of these processes could provide valuable guidance for river management. One crucial but frequently neglected secondary effect of LIDs is wood recruitment. Wood plays a fundamental role in forested river systems by enhancing both biotic and abiotic diversity. However, when large amounts of wood suddenly move, it can pose significant risks to infrastructures and communities. Therefore, monitoring and quantifying wood recruitment and its dynamics during and after such extreme events is essential. This contribution reports an overview of three case studies (one from Italy and two from Chile) regarding the assessment and quantification of wood recruitment and dynamics, intended as a cascading effect of LIDs in mountain catchments. In the Italian Alps, the Tegnas catchment (52 km2) was deeply affected by the Vaia Storm in 2018, which caused extensive debris flows, landslides, and tree windthrows along the slopes and floodplain, and it generated an exceptional flood in the main channel (RI > 50 yrs). Wood recruited from the banks was estimated using a GIS-based multi-disciplinary approach, first involving remote sensing and field data to quantify the tree biomass available, and then geomorphic change detection to estimate and quantify the role of erosion areas. In Chile, wood recruitment and mobility were analyzed in two catchments affected by volcanic eruptions, Chaitén in 2008 and Calbuco in 2015. The sources for wood recruitment were identified using satellite images complemented with previous research, while in-channel dynamics were analyzed using UAV and field surveys. In both basins (39 and 77 km2), cascading effects led to the massive transport of pyroclastic sediments toward downstream infrastructure, channel avulsions, and a significant increase in the availability of wood material for recruitment. Therefore, wood recruitment cannot be neglected when planning accurate and efficient hazard mitigation strategies in mountain catchments, and tools to monitor and measure wood dynamics with more accuracy are needed more than ever.