Extreme flood and landslides triggered in the Arroscia Valley (Liguria Region, Northwestern Italy) during the November 2016 rainfall event

From November 20th, 2016, to November 25th, 2016, Liguria Region (northwestern Italy) experienced prolonged and intense rainfall. The rainfall sequence occurred following two main phases. The second phase mainly hit the western sector of the region, reaching its peak on November 24th. Rainfall was particularly abundant within the Arroscia valley, where the 5–days cumulative rainfall locally exceeded 50% of the mean annual precipitation. In this paper, we document the rainstorm magnitude, presenting a first inventory of the rainfall–induced ground effects within the Arroscia Valley. The mapping was performed by means of extensive field work that was partly supported by satellite imageries. More than 250 landslides affected the upper sector of the valley, while in the downstream reach, widespread flood-related forms and processes resulting from the abundant precipitation were mapped. The results of this study are expected to be helpful for future research on both landslide– and flood–related channel change susceptibility and risk scenarios evaluation.