The frequency ratio and logistic regression models are applied and verified for analysis of debris flows susceptibility in a portion of the Dry Frontal Andes and Occidental Preandes of San Juan around 30°S latitude, by means of an investigation based on the Geographic Information System (GIS). The site under study covers an area of 2175.9 km2 with a debris flows area of 42.45 km2. For this purpose, thematic layers including debris flows inventory, lithology, elevation, slope, aspect, and solar radiation were used. The debris flow inventory map was prepared by interpreting aerial photographs and satellite images, supported by field surveys. Lithology was extracted from an existing geological map. Slope, aspect and solar radiation were calculated from a Digital Elevation Model created from SRTM (Shuttle Radar Topographic Mission) and Topographical maps. The relationship between the variables and the debris flows inventory was calculated using frequency ratio and logistic regression models. Both models helped produce debris flows susceptibility maps that classified susceptibility into five categories: very low, low, moderate, high and very high. Subsequently each debris flow susceptibility map was compared with known debris flows locations and tested. As a result, the frequency ratio model (accuracy is 82.71%) is better in prediction than logistic regression (accuracy is 75.64%) model for the high and very high categories. |