The importance of the precipitation and the susceptibility of the slopes for the triggering of landslides along the roads

In order to characterise the influence of the heavy rains on the observed l andslides during the 1996-1997 hydrological cycle, rainfall records for the last 100 years are analysed from 104 stations in eastern Andalusia. Regard ing the amounts of rain recorded between October 1996 and March 1997 in the 104 stations studied, 31 presented new all-time records; 15 presented valu es that were 80-100% of the pre-1995 record; 49 stations, 80-50%; and 9 sta tions, <50%. A map has been devised of the susceptibility of the materials through which the south-eastern Andalusian road network crosses, together w ith an inventory of the damage caused by instability phenomena on banks and cuttings of the road network during the winter of 1996-1997. The relations hips between the rainfall during the study period, the damage caused to the road network and the susceptibility of the materials affected are analysed . The results indicate that there is a clear correspondence between the rai nfall recorded and the susceptibility of the materials with the inventoried damage. It is concluded that the widespread serious damage caused in early 1997 to the roads and surrounding areas in the Alpujarra region and the co ast of the Province of Granada was mainly caused by the extraordinarily hea vy rains. However, considerably less damage was observed where the suscepti bility of the terrain is low, thus highlighting the extreme usefulness of t errain-susceptibility maps for risk prevention and territorial planning.