Simulating snowmelt-induced muddy debris flows in alpine regions: A case study in the Seres Creek, Dolomites

Mountainous catchments often experience snowmelt-induced landslides and debris flows triggered by soil saturation due to intense and rapid snowmelt during spring and early summer. These events are influenced by snowpack dynamics, terrain morphology, and the hydrological processes associated with the melting process. While snowmelt-induced debris flows typically exhibit gradual initiation due to steady water input, they can mobilize large volumes of sediment (and possibly woody material), posing significant hazards to downstream areas. In spite of their impacts, these events are poorly covered in the literature. The objectives of this study are to examine the mechanisms of snowmelt-induced debris flow formation, analyze sediment transport dynamics, and evaluate downstream impacts. The landslide has affected sedimentary rocks of poor mechanical characteristics that produce abundant silty-clayey debris. The event under study occurred on June 17-18, 2024 in the Dolomites, just upstream of the Longiarù village (South Tyrol, Italy). Field observations, coupled with DoD analysis, revealed that the landslide originated in a hollow near the watershed divide and the muddy debris flow traveled a significant distance into the valley, receiving further water input from a few minor streams and entraining additional sediments along its course. Video footage recorded near the village showed a progressive decrease in flow concentration as the flowing mass moved downstream.

Based on the mobilized volume derived from the DoD, we simulated the debris flow using the single-phase flow model implemented in the r.avaflow computational tool. Field data and historical records were used to calibrate and validate the model, ensuring that the simulated results closely matched observed travel distances, deposited volumes, and impacted areas. The findings of this study contribute to a broader understanding of snowmelt-induced debris flows in mountain regions and provide insights for developing effective hazard mitigation strategies.