The October 2000 flooding in Valle d'Aosta (Italy): Event description and land planning measures for the risk mitigation

Abstract

On October 13-16th, 2000 heavy rainfalls in the Northwestern Italian Alps caused huge flooding and landslides with significant damages to houses and infrastructures and several life losses. In this paper a description of the main events that affected Valle d'Aosta's region and the subsequent land planning measures adopted for the risk mitigation are presented.After a first meteorological and hydrological framing, based on the data of the regional monitoring system (that pointed out rainfalls up to 236 mm in 24 h also in high-altitude zones, because of the rise of the isotherm 0 • C around 3000 m above sea level), the main effects of the event (extensive flooding, landslides, soil slips and debris flows) in the regional catchment of the Dora Baltea river are described.Through aerial and direct surveys those effects have been transferred into a thematic cartography within two months from the event, in order to have detailed elements for the technical, administrative and political land planning decisions, and, on this basis, a new regional directive containing detailed measures for the hydro-geological risk mitigation and land safety has been adopted.

Flood Risk Management in Rivers and Torrents

“…This improves the data management during the events through the consecutive issue of bulletins to the civil protection offices, updating the measured data and their trend, allowing the decision-making processes based on the more probable scenario (Ratto et al 2003). However, it has been observed that the alert system, organized by Regione Piemonte Authority, and people preparedness hugely contributed to reduce the total number of victims.…”

“…The soil moisture conditions play one of the major roles in the rainfallsrunoffs transformation, together with the rainfalls intensities, their geographical distributions, and, in some cases, the snowmelt. For instance the 2000 (October 13 rd -16 th ) flood would have been probably more severe if the drop in temperature did not transform the rainfalls precipitations into snow (Ratto et al, 2003), when the thermometric zero dropped from about 2800 m a.s.l. to about 1500 m a.s.l., in alpine regions.…”

“…On October 13-16th, 2000 heavy rainfalls interested the North-western Italian Alps from the upstream reach of the Po river to the Ticino river, causing huge flooding and landslides with significant damages to houses and infrastructures and several life losses (Ratto et al, 2003).…”

A multi-centennial record of past floods and earthquakes in Valle d'Aosta, Mediterranean Italian Alps

“…Buzzi and Foschini, 2000;Lionello et al, 2012). Spatially restricted convective and spatially more exhaustive cyclonic precipitation events may lead to catastrophic floods (Gaume et al, 2009;Marchi et al, 2010), as for instance occurred in October 2000 or June 1957 (Ratto et al, 2003). Moreover, the south-western European Alps are in a seismogenic region that experienced strong earthquakes with macroseismic Medvedev-Sponheuer-Kárník (MSK) intensities up to IX and estimated magnitudes higher than 6, e.g.…”

Research developments in debris flow monitoring, modelling and hazard assessment in Italian mountain catchments

“…During the May 1998 event in the Pizzo d'Alvano massif (Sarno, Southern Italy), hundred of soil slip-debris flows were triggered and impacted on the urbanised areas at the base of the massif, causing serious damage and numerous victims [6]. The October 2000 flooding and debris flow event in Valle d'Aosta: several villages were buried caused numerous victims [41]. In this paper, the most recent research developments relating to debris flow studies in Italy are reviewed.…”