Remote sensing and GIS data applied to debris flow and debris flood susceptibility in the northeastern sector of the city of Santiago (33°20.51' S - 70°28.16' W)

Debris flows and debris floods are the most significant geological and geomorphological hazards in the foothills and mountain areas of Santiago. In recent decades, the most devastating events have been triggered by intense precipitation for short periods and thermal anomalies, affecting the population and causing fatalities and significant damage to infrastructure and natural ecosystems. Based on satellite and cartographic data, the analysis of conditioning factors and the use of Geographic Information Systems (GISs), the susceptibility to debris flows and debris floods in the Arrayán and Gualtatas creek basins (Santiago, Metropolitan Region of Chile) was determined. The susceptibility index (SI) was calculated using qualitative and quantitative methodologies, based on the sum of the weighted scores of 14 conditioning factors grouped into three categories (geology, geomorphology, and soil conditions). The level of importance of each factor was determined using the Analytical Hierarchical Process (AHP). The debris flow and debris flood generation susceptibility index map obtained for the study area indicates that 60.78% of the area has low to very low susceptibility, 23.64% has moderate susceptibility, and 15.58% has high to very high susceptibility. The latter is located at the headwaters of the basins, valley bottoms, steep slopes, and the main watercourses and streams and has records of recent debris flow events in urban areas. Freely available satellite data and GIS tools contribute to land use planning to determine possible areas of debris flow and debris flood generation that may affect the population of the northeastern sector of Santiago.