Comparison of landslide forecasting services in Piedmont (Italy) and Norway, illustrated by events in late spring 2013

摘要

Only few countriesoperate systematically national and regional forecasting servicesfor rainfall-induced landslides (i.e., debris flows, debris avalanches andshallow slides), among them Norway and Italy. In Norway, the Norwegian WaterResources and Energy Directorate (NVE) operates a landslide forecastingservice at national level. In Italy, the Regional Agency for EnvironmentalProtection, ARPA Piemonte, is responsible for issuing landslide warnings forthe Piedmont region, located in northwestern Italy. A daily hazard assessmentis performed, describing both expected awareness level and type of landslidehazard for a selected warning region. Both services provide regular landslidehazard assessments based on a combination of quantitative thresholds anddaily rainfall forecasts together with qualitative expert analysis. Dailywarning reports are published athttp://www.arpa.piemonte.gov.it/rischinaturali andhttp://www.varsom.no, last access: 7 May 2018.In spring 2013, ARPA Piemonte and the NVE issued warnings forhydro-meteorological hazards due to the arrival of a deep and largelow-pressure system, called herein Vb cyclone. This kind of weathersystem is known to produce the largest floods in Europe. Less known is thatthis weather pattern can trigger landslides as well.In this study, we present the experiences of NVEand ARPA Piemonte in the late spring of 2013. The Vb cyclone influenced weatherthroughout Europe over a long period, from the end of April until the beginning ofJune 2013. However, major affects were observed in the first half partof this period in Piedmont, while in Norway, major damage was reportedfrom 15 May to 2 June 2013. Floods and landslidessignificantly damaged roads, railways, buildings and otherinfrastructure in both countries.This case study shows that large synoptic pattern can produce differentnatural hazards in different parts of Europe, from sandstorms at low latitudes, to flood andlandslides when the system moves across the mountain regions. Thesesecondary effects were effectively forecasted by the two landslide warningservices, operating in different parts of Europe. The landslide risks were also properlycommunicated to the public some days in advance. This analysis hasallowed the establishment of fruitful international collaboration between ARPAPiemonte and NVE and the future exchange of experiences, procedures andmethods relating to similar events.