The gully system on the NW sector of La Fossa cone (Vulcano Island): 2D evolution and hazard implication

The Island of Vulcano is the emerged portion of a composite volcanic edifice within the Aeolian volcanic archipelago, situated in the southern Tyrrhenian Sea. The remobilization, triggered by heavy rainfall, of loose volcaniclastic material from La Fossa cone and the generation of small debris flows are recurrent hazards on Vulcano. Although these debris flows generally transport small volumes of material, in the case of severe events, they can be channeled along the roads, flood several buildings, inundate the main harbor, and eventually be discharged into the sea. Gravitational and erosive processes, mainly due to rainfall, have formed several gully systems around the La Fossa cone. The presence of gully systems along slopes enhances both runoff and downslope mass wasting, and, above all, the gullies themselves act as a source of mass wasting due to the collapse of their walls and the processes of aggradation and degradation of their beds. Therefore, understanding the behaviour of gullies and their response to rainfall is crucial for predicting the effects of environmental changes, whether climatic or volcanic, on gully dynamics.In the frame of "VOlcaniclastic debris flows at La Fossa cone (Volcano Island): evolution and hazard implication (VOLF)" project funded by the Istituto Nazionale di Geofisica e Vulcanologia, we here analyze aerial photos of the NW sector of La Fossa cone to describe the evolution of its gully system from the 1954 to 2022. First, we create a georeferenced dataset of photos by orthorectifying existing photos and generating new ones through the Structure from Motion (SfM) method applied to Unmanned Aerial System (UAS) photos. Second, we describe the geomorphological features of the gullies in the NW sector of La Fossa cone, identifying features to be parameterized. Finally, we qualitatively and quantitatively describe their evolution over almost 70 years.This work aims to investigate the morphological evolution of the NW flanks of La Fossa cone, a crucial aspect for assessing hazards associated with volcaniclastic sediment-charged flows and floods on Vulcano Island. This is especially relevant in a scenario where ongoing climate changes may potentially disturb the current equilibrium, heightening the likelihood of short-term extreme rainfall events.