Rainfall events with shallow landslides in the Entella catchment (Liguria, Northern Italy)

Abstract

Abstract. In the recent decades, the Entella River basin, in the Liguria Apennines, Northern Italy, was hit by numerous intense rainfall events that triggered shallow landslides, soil slips and debris flows, causing casualties and extensive damage. landslides occurred primarily at the same time or within six hours from the maximum peak rainfall intensity, and at or near the geographical location where the rainfall intensity was largest. Adopting a Frequentist approach, we define the event rainfall intensity-event duration ID, threshold for the possible initiation of shallow landslides and debris flows in the Entella 20River basin. The threshold is lower than most of the thresholds proposed in the literature for similar mountain catchments, local areas and single regions in Italy. Analysis of the antecedent rainfall conditions for different periods, from 3 to 15 days, revealed that the antecedent rainfall did not play a significant role in the initiation of landslides in the Entella catchment. We expect that our findings will be useful in regional to local landslides early warning systems, and for land-planning aimed at reducing landslides risk in the study area. 25

Data limitations and potential of hourly and daily rainfall thresholds for shallow landslides

“…Additionally we also define total rainfall E versus duration D (ED) thresholds in the form of a power law function, E = a • D b , by optimising the two parameters a and b through TSS maximisation. As a reference, we provide also the results for the thresholds defined following the frequentist approach, first introduced in Brunetti et al 2010, which is one of the most widely used methods for ED fitting (e.g., Peruccacci et al, 2012;Vennari et al, 2014;Gariano et al, 2015;Iadanza et al, 2016;Melillo et al, 2018;Roccati et al, 2018). The optimum threshold in this case is based on triggering events only.…”