Abstract ID: 3.9622 | Accepted as Talk | Talk/Oral | TBA | TBA

In the Eastern Italian Alps, the summer of 2023 has been particularly severe in terms of precipitation, with many intense thunderstorms concentrated in July and August. Several river basins within the Ortles-Cevedale massif were hit and have been affected by landslides, debris flows, and floods. Here, we describe the effects of a severe thunderstorm that hit the Ortles-Cevedale area on August 27th – 28th, 2023, reporting a few examples of the events registered in different locations. Data analysis of the precipitation event indicated a 48-hours cumulated rainfall ranging between 95 mm and 144 mm. Temperatures were always above zero, and the zero-degree isotherm ranged between 3’725 m a.s.l. and 3’330 m a.s.l. Most severe transport events were registered in the Sulden, Trafoi, and Forni valleys, and seem to have been directly influenced by the dynamics acting in the proglacial and periglacial areas of the corresponding glaciers. In the Trafoi and Sulden regions, the sediment-transport events were initiated as erosion on the moraines, either as deepening and widening of existing gullies, as well as moraine toe erosion by the proglacial stream. First estimates of the volumes mobilized during this rainfall event amounted to ca. 120’000 m3 (60’000 m3 in each catchment). In Trafoi, the sediment accumulated in the valley bottom damaged a famous touristic destination with an important historical and cultural significance. In the Sulden proglacial area, the sediment mobilized during this event completely outbalanced the system, for which previous estimates indicated a total mobilized volume of ca. 108.000 m3 for the 2005-2021 time period. Considering the morphological evolution of proglacial areas, and the potential amount of sediment that can be mobilized in these regions, the understanding of the sediment dynamics linked to extreme precipitation events will become crucial in a warming world, as intense rainstorms will likely become the primary triggers for severe and important sediment-transport events.