REGIONAL-SCALE DEBRIS-FLOW RISK ASSESSMENT FOR AN ALPINE VALLEY — IJEGE
 
 
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REGIONAL-SCALE DEBRIS-FLOW RISK ASSESSMENT FOR AN ALPINE VALLEY



Abstract:
In this paper, we perform a societal and economic risk assessment for debris flows at the regional scale, for lower Valtellina, Northern Italy. We apply a simple empirical debris-flow model, FLOW-R, which couples a probabilistic flow routing algorithm with an energy line approach, providing the relative probability of transit, and the maximum kinetic energy, for each cell. By assessing a vulnerability to people and to other exposed elements (buildings, public facilities, crops, woods, communication lines), and their economic value, we calculated the expected annual losses both in terms of lives (societal risk) and goods (direct economic risk). For societal risk assessment, we distinguish for the day and night scenarios. The distribution of people at different moments of the day was considered, accounting for the occupational and recreational activities, to provide a more realistic assessment of risk. Market studies were performed in order to assess a realistic economic value to goods, structures, and lifelines. As terrain unit, a 20 m x 20 m cell was used, in accordance with data availability and the spatial resolution requested for a risk assessment at this scale. Societal risk the whole area amounts to 1.98 and 4.22 deaths/year for the day and the night scenarios, respectively, with a maximum of 0.013 deaths/year/cell. Economic risk for goods amounts to 1,760,291 €/year, with a maximum of 13,814 €/year/cell.

Authors:
Serena Lari - Università degli Studi di Milano Bicocca - Dep. Geologic Sciences and Geotechnologies - Milan, Italy
Giovanni B. Crosta - Università degli Studi di Milano Bicocca - Dep. Geologic Sciences and Geotechnologies - Milan, Italy
Paolo Frattini - Università degli Studi di Milano Bicocca - Dep. Geologic Sciences and Geotechnologies - Milan, Italy
Pascal Horton - Institut de géomatique et d'analyse du risque (IGAR), Unil, Lausanne – Switzerland
Michel Jaboyedoff - Institut de géomatique et d'analyse du risque (IGAR), Unil, Lausanne – Switzerland
Keywords
Economic risk, societal risk, regional scale risk assessment, debris flow modelling
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