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).
