Estimation of rainfall thresholds triggering shallow landslides for an operational warning system implementation

Abstract

The Piemonte regional warning system service, managed by the Environmental Protection Agency of Piemonte ("ARPA Piemonte" as official Italian acronym), is based on an advanced meteo-hydrological automatic monitoring system, and it is integrated with forecasting activities of severe weather-related natural hazards. At present, a meteo-hydrological chain is operated to provide flood forecasting on the main river pattern. The development of a forecasting tool for shallow landslides triggered by heavy rainfall is presented. Due to the difficulties in modelling shallow landslides triggering in a large and complex area like the Piemonte region, an empirical model is developed on the basis of the correlation between rainfall and previous landslides in historical documents. The research focuses on establishing rainfall thresholds for landslides triggering, differentiating the critical rainfall values through a geological characterisation of the different territories. The period from 1990 to 2002 is considered. A total number of 160 landslides with hourly information and time of triggering are used to calibrate the system. As a first outcome, two different zones have been identified: (1) zones in alpine environments, principally characterised by a bedrock composed of metamorphic rocks, igneous rocks, dolostones or limestones that require high values of critical rainfall and (2) zones in hilly environments, principally characterised by sedimentary bedrock that require low values of critical rainfall. Verification has been performed on a total number of 429 landslides with known date of occurrence. The results show a good agreement with the model with no missed alarms and a very low number of false alarms, thus suggesting an effective operational implementation.

Basic features of the predictive tools of early warning systems for water-related natural hazards: examples for shallow landslides

“…Rainfall is often interpreted merely statistically, with an empirical quantification of rainfall thresholds for landslide initiation (e.g., Sirangelo and Versace, 1996;Sirangelo and Braca, 2004;Guzzetti et al, 2007Guzzetti et al, , 2008Capparelli and Tiranti, 2010;Tiranti and Rabuffetti, 2010;Martelloni et al, 2012;Segoni et al, 2014;Tiranti et al, 2014;Piciullo et al, 2017). In rare cases, physically based approaches are adopted for the interpretation of the effects of rainfall history.…”

Technical Note: An operational landslide early warning system at regional scale based on space–time-variable rainfall thresholds

“…At regional scale, warning systems for rainfall-induced landslides are mainly based on empirical rainfall thresholds (Keefer et al, 1987;Aleotti, 2004;Hong et al, 2005;Tiranti and Rabuffetti, 2010;Baum and Godt, 2010;Capparelli and Tiranti, 2010;Cannon et al, 2011;Floris et al, 2012;Jakob et al, 2012;Staley et al, 2013;Lagomarsino et al, 2013;Tiranti et al, 2014;Cucchi et al, 2015). A broad literature exists on empirical rainfall thresholds for the possible initiation of landslides (Guzzetti et al, 2007, and references therein), and intensity-duration (I -D) thresholds are the most popular (Caine, 1980;Guzzetti et al, 2008;and references therein).…”

Adapting the EDuMaP method to test the performance of the Norwegian early warning system for weather-induced landslides

“…Rainfall-induced warning systems for landslides are, by far, the most diffuse class of LEWSs operating around the world. LEWSs can be employed at two distinct scales of analysis: "local" and "regional" (ICG, 2012;Thiebes et al, 2012;Calvello et al, 2015;Stähli et al, 2015). EWSs at a regional scale for rainfall-induced landslides have become a sustainable risk management approach worldwide to assess the probability of occurrence of landslides over appropriately defined wide warning zones.…”

“…EWSs at a regional scale for rainfall-induced landslides have become a sustainable risk management approach worldwide to assess the probability of occurrence of landslides over appropriately defined wide warning zones. In fact, during the last decades, several systems have been designed and improved, not only in developing countries (UNISDR, 2006;Chen et al, 2007;Huggel et al, 2010; among others) but also in developed countries (NOAA-USGS, 2005;Badoux et al, 2009;Baum and Godt, 2010;Osanai et al, 2010;Lagomarsino et al, 2013;Tiranti and Rabuffetti, 2010;Rossi et al, 2012;Staley et al, 2013;Calvello et al, 2015;Segoni et al, 2015). As a recent example, the Norwegian LEWS was launched in autumn 2013 by the Norwegian Water Resources and Energy Directorate (NVE).…”