Application of an analog downscaling technique to the assessment of futurelandslide activity - a case study in the Italian Alps

Slope stability and hence landslide activity is in many cases related to cl imate, which influences groundwater and pore pressure fluctuations of hills lopes. An approach is presented which transforms transient GCM output by st atistical downscaling to local precipitation scenarios, which together with directly derived temperature scenarios are subsequently fed into a slope h ydrological/stability model to derive future landslide activity. This model chain is applied to a landslide in the Dolomites, Italy. Validation of the approach against independent observed records suggests its applicability f or estimating future landslide activity based on GCM results. One possible way of estimating the quality of the approach is to determine sources of un certainty introduced by the GCM simulations and by different fitting period s of the downscaling technique. Differences between the GCM experiments are found to be more important than differences between the 2 fitting periods. The most striking result is the significant reduction of landslide activit y in spring in all cases. This is attributable to the rise of winter temper ature which impedes future storage of winter precipitation as snow. As one consequence, less melt water is available for the hillslope in spring, caus ing the decrease in activity. It can be concluded that differences between GCMs and differences between fitting periods permit quantification of part of the uncertainty inherent in climate change impact assessments. Impacts w hich emerge in all model combinations, such as the decrease in landslide ac tivity in spring shown here, have a high level of confidence.