In Italy, as a response to a huge landslide event occurred in Sarno in 1998 (Cascini 2004), a national law has been written on landslide and flood risk mitigation measures (DPCM, 2004). Beside the national system, following the national law, in each Italian Region all the Regional Departments for Civil Protection (DPC) have designed a hydro-geological early warning system. The duty of the Functional Regional Centres of the regional DPC is, therefore, to handle and analyse weather forecast data, meteorological and hydrogeological variables. Qualitative and quantitative data are collected from: weather and hydro-pluviometric networks; a national meteorological radar network; various satellite platforms available for earth observation; geological geomorphological and meteorological modelling. Main activities are oriented at operating and upgrading the landslide early warning system through the definition of: warning zones and related rainfall thresholds; rainfall precursors and relative threshold values; hydraulic indicators and threshold values. The service provided by the Functional Centres in real time is carried out through a two-phase weather forecast and monitoring strategy, implemented in a coordinated and integrated way. The first phase is composed by a meteorological analysis, through numerical modelling and, by the evaluation of the effects of hazardous hydrogeological phenomena in terms of risk to the population, buildings, infrastructures and the environment. The weather forecast and the evaluation of the rainfall amount, in terms of height, is provided to the Functional Centres by different agencies, by means of the following tools and models: ECMWF 12, ECMWF ENSEMBLE, LAMI, LAMI 00 and 12, METEOSAT, NEFODINA, NEFOMEDI, IXEUR, Grazzanise RADAR, LIGHTNING DETECTOR, AIR FORCE CARDS, CARDS MetOffice, radiosonde SEA PRACTICE, Prometheus. The second phase includes: i) the qualitative and quantitative evaluation of meteorological and hydrological events based on monitoring data. In each region the Functional Centre manages its own network of pluviometer and hydrometric sensors. The purpose of these regional LEWSs is to provide a continuous service throughout the year, working 24/7 when appropriate, in order to inform authorities responsible for warnings issuing and emergency management. In the majority of the Italian regional systems the municipality is the minimum territorial unit for warning issuing and, a reference pluviometer with a set of rainfall thresholds has been defined. The threshold values selected for the activation of the warning levels of attention, pre-alarm and alarm, have been estimated considering reference return periods equal to 2, 5 and 10 years, respectively.

However, some Italian Regions have developed their own rainfall thresholds and early warning model in cooperation with Universities or institutions. Relevant experiences have been carried out for: Emilia Romagna (Berti et al., 2012; Martelloni et al., 2012; Lagomarsino et al., 2013), Toscana (Segoni et al., 2014); Piemonte (Tiranti and Rabuffetti, 2010; Tiranti et al., 2014), Calabria (Sirangelo et al., 2003; Greco et al., 2013), Umbria (Ponziani et al., 2013). The details about the warning models employed in these systems will be discussed in the following sections.