Municipal landslide risk assessment (AGGREGATION CH 6)

Abstract

Detailed geomorphological mapping provides information on the site-specific conditions under which different landslide types occur in various parts of the study area. Landslides are concentrated along the Caujerí scarp, but also in the coastal hills and in the northern part of the Baitiquirí area. There, the landslides have different characteristics and causative factors. Subdivision of the terrain into 603 terrain mapping units, individual homogeneous polygons, allowed for a more detailed characterization of the terrain than would be possible through conventional map-overlay of main factor maps. The boundaries of different landslide parts were surveyed by photo-interpretation, and landslides were described in the field from a detailed checklist, where information was collected related to landslide type, subtype, relative age, and depth. This data set enable us to generate a heuristic model, using multi-criteria analysis, which was successful in classifying the area into different hazard classes, which can be displayed either in ten more detailed or three generalized classes, depending on the user needs. Improvements in the method could be made if different weight maps were produced for different landslide types. The qualitative hazard assessment was converted into probabilistic values including event, spatial and temporal probabilities.