Impact of climate change on slope stability using expanded downscaling

Climate parameters affecting ground water and pore pressure fluctuations can, in many cases, trigger slope instability and hence landslide activity. Global warming due to the greenhouse effect and especially changes in precipitation patterns and air temperature might therefore have influences on future landslide activity. The present paper shows an assessment of climate change consequences for displacement rates of a mudslide in the Dolomites, Italy. The study is based on climate projections of a general circulation model (GCM). GCMs are able to successfully reproduce large-scale patterns of climate, while they show a poor performance on the regional scale. Therefore, GCM output is postprocessed with a statistical downscaling technique to derive local-scale climate change information from simulated atmospheric circulation patterns of the European-North Atlantic sector. The resulting precipitation and temperature series are introduced in a hydrological tank model, which calculates daily groundwater levels. Based on the groundwater data, a visco-plastic rheological model is applied to derive displacement rates of the mudslide as final output. The climate change signal is most pronounced for air temperature, while it is weaker but still significant for yearly precipitation, which is decreasing. As a consequence, yearly displacement rates show a significant reduction. The most dramatic changes, however, occur in spring with strongly lowered groundwater levels and consequently decreasing displacement rates. This is seen as an effect of reduced storage of winter precipitation as snow and hence decreasing meltwater amounts in early spring. The presented model chain with statistical downscaling, hydrological and rheological models allows the assessment of future landslide displacement affected by the greenhouse effect. The results, however, have to be taken with caution since in all parts of the model chain there are uncertainties that are difficult to address. (C) 2000 Elsevier Science B.V. All rights reserved.