Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/nhessd-3-269-2015
© Author(s) 2015. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
08 Jan 2015
Review status
This discussion paper has been under review for the journal Natural Hazards and Earth System Sciences (NHESS). The manuscript was not accepted for further review after discussion.
The alerting system for hydrogeological hazard in Lombardy Region, northern Italy: rainfall thresholds triggering debris-flows and "equivalent rainfall" method
A. Cucchi1, I. Q. Valsecchi1, M. Alberti1, P. Fassi1, M. Molari2, and G. Mannucci2 1Lombardia Informatica, Regione Lombardia, Centro Funzionale Monitoraggio Rischi, Sala Operativa di Protezione Civile, via Rosellini 17, 20124 Milano, Italy
2Regione Lombardia, D. G. Sicurezza, Protezione Civile e Immigrazione, U. O. Protezione Civile, Struttura Gestione emergenze, Piazza Città di Lombardia 1, 20124 Milano, Italy
Abstract. The Functional Centre (CFMR) of the Civil Protection of the Lombardy Region, North Italy, has the main task of monitoring and alerting, particularly with respect to natural hazards. The procedure of early warning for hydrogeological hazard is based on a comparison of two quantities: thresholds and rainfall, both referred to a defined area and an exact time interval.

The CFMR studied 52 landslide events (1987–2003) in Medium-Low Valtellina and derived a model of the critical detachment rainfall, in function of the local slope and the Curve Number CN (an empirical parameter related with the land cover and the hydrological conditions of the soil): it's physically consistent and allows a geographically targeted alerting. Moreover, rainfall thresholds were associated with a typical probability of exceedance.

The processing of rainfall data is carried out through the "equivalent rainfall" method, that allows to take into account the antecedent moisture condition of the soil: in fact the hazard is substantially greater when the soil is near to saturation. The method was developed from the CN method and considers the local CN and the observed rainfall of the previous 5 days. The obtained value for the local equivalent rainfall, that combines rainfall (observed and forecasted) and local soil characteristics, is a better parameter for the evaluation of the hydrogeological hazard.

The comparison between equivalent rainfall and thresholds allows to estimate the local hydrogeological hazard, displayed through hazard maps, and consequently to provide a reliable alerting activity (even localized to limited portions of the region).


Citation: Cucchi, A., Valsecchi, I. Q., Alberti, M., Fassi, P., Molari, M., and Mannucci, G.: The alerting system for hydrogeological hazard in Lombardy Region, northern Italy: rainfall thresholds triggering debris-flows and "equivalent rainfall" method, Nat. Hazards Earth Syst. Sci. Discuss., 3, 269-290, doi:10.5194/nhessd-3-269-2015, 2015.
A. Cucchi et al.
A. Cucchi et al.

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Short summary
The Functional Centre (Civil Protection, Lombardy region, Italy), from landslide data in Valtellina, developed a physically consistent model of the critical detachment rainfall, in function of the local slope and the Curve Number. The “equivalent rainfall” method, which considers both observed and forecasted rainfall (in order to take into account the soil antecedent moisture conditions), allows to display hydrogeological hazard maps, useful to provide a reliable and localized alerting activity.
The Functional Centre (Civil Protection, Lombardy region, Italy), from landslide data in...
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