Cost-based analysis of mitigation measures for shallow-landslide risk reduction strategies

Landslide risk assessments are usually permeated by a certain degree of subjectivity. In order to reduce it, we have developed an original methodology which enables risk assessments to be carried out in fully quantitative terms, integrating both physical and economic science techniques. This risk assessment combines geomorphological studies, probabilistic modelling and cost-benefit analyses (CBA). We applied the methodology to an area of north-west Italy that was affected in 2011 by a dramatic rainfall-induced landslide event, and where a risk management program is necessary for avoiding future losses. We analyzed the cost-effectiveness of several landslide mitigation measures applying the proposed procedure. The results demonstrate that measures previously considered as suitable for mitigating shallow landslides were inappropriate from the economic viewpoint. The applied techniques also served to optimize economically the most appropriate mitigation measure. Moreover, our methodology allowed to calculate the maximum affordable investment on a cost-effective mitigation measure; this result will be a reference for designing innovative solutions to mitigate landslides in the study area.