Background

In Italy, landslides are triggered by intense and/or prolonged rainfall. The spatial and temporal forecast of multiple landslides triggered by rainfall in wide areas relies primarily on empirical rainfall thresholds. It is widely believed that the thresholds are influenced by the local topographic (morphological), lithological, soil, and climatic settings. For this reason, it is necessary to define local rainfall thresholds. Reliable local thresholds require a large amount of information on rainfall-induced landslides in the considered area. Rainfall thresholds can be used in early warning systems for the prediction of the occurrence of rainfall-induced landslides. To respond to a request of the Italian national Department for Civil Protection (DPC), CNR IRPI designed and developed SANF, an Italian acronym for National Early Warning System for Rainfall Induced Landslides. SANF forecasts the possible occurrence of landslides by comparing rainfall measurements and forecasts with empirical rainfall thresholds at national scale. The SARF Sardegna project aims at (i) defining ED (cumulated event rainfall-rainfall duration) empirical thresholds for the possible initiation of rainfall-induced landslides in the Sardinia region, and (ii) implementing the landslide regional warning system in the Sardinia region. Future developments of the project involve the use of regional and local thresholds in the landslide warning system.

Purpose

Goals of the project are:

• The collection, organization and analysis of information on rainfall-induced landslides in the Sardinia region;
• The definition of objective and reproducible empirical rainfall thresholds for the possible landslide occurrence in the regional territory and in sub-regional areas;
• The implementation of the regional landslide warning system for the Sardinia region (SARF Sardegna).

Methods

A large amount of information on rainfall-induced landslides is required to define reliable rainfall thresholds. Information will be obtained searching mainly from chronicle sources (national and local newspapers available online), technical reports of landslide events compiled by local civil protection authorities.
CNR IRPI started a collaboration with the local fire brigades to collect reports of actions after landslide events.
Rainfall thresholds will be defined using a frequentist method. The method allows calculating objective and reproducible thresholds corresponding to different exceedance probabilities.

Products

• Catalogue of rainfall events that triggered landslides in the Sardinia region;
• Regional and sub-regional ED (cumulated event rainfall-rainfall duration) empirical rainfall thresholds.
• A regional landslide warning system for the Sardinia region (SARF Sardegna).

Conclusions

We expect that the results of the SANF Sardegna project may contribute to mitigate – through prevention – landslide risk reducing the number of fatalities and injured people caused by rainfall-induced landslides in the Sardinia region.