Assessing the effect of mitigation measures on landslide hazard using 2D numerical runout modelling.

Landslidemitigationmeasures are used to reduce the risk affectingmountain communities. The quantitative estimation of the change or reduction in risk, after implementing mitigation measures, requires modeling of past events and the forward prediction of possible future occurences. However, the forward-prediction of landslide hazard is subjected to uncertainties due to the lack of knowledge on some key aspects like the possible source volume that can be triggered andmodel parameters that determine the landslide runout. In this study, a back-analysis of a debris flow event was carried out using MassMov2D to create a set of parameter ranges for forward-predicting runouts with mitigationmeasures.Weapproached the issue of uncertainty by systematically sampling parameters from wide ranges and running hundreds of different runout scenarios. Simulations from back-analysiswere comparedwith the forward-predicted models to determine changes in the spread and intensity of debris flows affecting elements at risk (e.g. houses and roads). This study is a first step towards a quantitative risk assessment (QRA) being carried out within the EC FP-7 funded CHANGES network (Grant Agreement No. 263953).