Landslide susceptibility zoning for risk analysis using a geographical information system (GIS) in the Jerte Valley (Spanish Central System)

The Jerte Valley is a linear tectonic depression (NE-SW), generated by several fracture systems associated with the Odemira-Plasencia fault which is one of the most important in the Iberian Peninsula. One of the most significant processes in the Quaternary evolution of this valley is that of mass movements. An analysis of the natural factors controlling these processes in this area reveals that, in current conditions, major mass movements are unlikely to be generated. However, our working hypothesis considers that a phenomenon with catastrophic consequences is feasible, chiefly due to anthropic activity; in recent years there has been a process of replacement of the natural vegetation with cherry-tree plantations and considerable urban and road infrastructure development. Therefore we have commenced a series of studies on landslide hazards in the Jerte Valley. The first step, the results of which we present here, was to divide the area into zones based on the values of certain causality indices or factors (what some authors call zonal susceptibility or propensity). The cartographic zoning was carried out using a CIS which, based on the most standardised procedures.