Article Eighty Years of Data Collected for the Determination of Rainfall Threshold Triggering Shallow Landslides and Mud‐Debris Flows in the Alps Fabio Luino 1, Jerome De Graff 2, Anna Roccati 1,*, Marcella Biddoccu 1, Chiara Giorgia Cirio 1, Francesco Faccini 1,3,* and Laura Turconi 1 1 Istituto di Ricerca per la Protezione Idrogeologica, Consiglio Nazionale delle Ricerche, Strada delle Cacce 73, 10135 Torino, Italy;
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[email protected] (L.T.) 2 Department of Earth & Environmental Science, California State University, M/S ST24, Fresno, CA 93740, USA;
[email protected] 3 Dipartimento di Scienze della Terra, dell’Ambiente e della Vita, Università di Genova, corso Europa 26, 16132 Genova, Italy * Correspondence:
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[email protected] (F.F.); Tel.: +39‐010‐3538039 (F.F.) Received: 22 November 2019; Accepted: 27 December 2019; Published: 31 December 2019 Abstract: Identifying the minimum rainfall thresholds necessary for landslides triggering is essential to landslide risk assessment. The Italian Alps have always been affected by shallow landslides and mud‐debris flows, which caused considerable damage to property and, sometimes, casualties. We analysed information provided from different sources carrying on the most thorough research conducted for this alpine area. Thousands of documents and reports of rainfall values recorded over 80 years by rain gauges distributed in Sondrio and Brescia Provinces define the mean annual precipitation (MAP)‐normalized intensity–duration thresholds for the initiation of shallow landslides and mud‐debris flows.