Landslide susceptibility models utilising spatial data analysis techniques. A case study from the lower Deba Valley, Guipuzcoa (Spain)

A quantitative methodology for landslide susceptibility zonation is described and its application to a study area in the lower part of the Deba Valley ( Guipuzcoa, Spain) presented. Susceptibility models were obtained on the basis of statistical relationships between known mass movements and conditioning factors. A landslide rupture hypothesis was set and a digital database consisting of seventeen causal factors layers constructed. The modelling procedure was implemented utilising a GIS. The susceptibility analysis method is based on the Favourability Functions approach, and two different mathematical frameworks: probability theory and Zadeh's fuzzy set theory. Several landslide susceptibility models were produced and validated using different sets of independent landslide data. The predictive capability of models was determined.