Investigating the geomorphic change in the Rio Cordon basin (Italy) after Vaia Storm

ABSTRACT: natural disturbances are the cause of major instabilities for river systems as they can rapidly overturn the morphological features of the landscape at various spatial scales. On October 29th, 2018, an extreme event named “Vaia” characterized by heavy rainfall and wind gusts reaching 200 km h-1 affected part of North-Eastern Italy. Following the cascading processes caused by this event, several alpine catchments in the area featured significant geomorphic changes. The Rio Cordon catchment (5 km2 ), located in the Agordino area (NE of Italy), is one of the few alpine catchments offering a long-term monitoring station for climatic conditions and sediment fluxes. After Vaia Storm, large amount of sediment was deposited into the storage area of the measuring station, where a volume of ~ 8000 m3 was measured. To understand the causes of such massive sediment transport, the present work aims at assessing qualitatively and quantita tively the variation of sediment source areas, as well as the channel geomorphic changes. Three different steps were performed at catchment scale: i) update the sediment sources inventory; ii) DoD analysis; and iii) connectivity analysis to verify the (de)coupling of the sediment sources. Pre liminary results showed the activation of several sediment sources, responsible for sediment contri bution to the channel network. In particular, large lateral erosions within the main channel and the disruption of the armoured layer of the river bed seem to have represented the primary source of sediment. The results permitted to describe the geomorphic response of a high mountain basin to an extreme event, offering information for future management decisions.