Drone systems for landslide hazard assessment in Quito

Landslides are a frequently occurring geo-hazard in Quito, Ecuador, with over 800 reported from 2005 to 2014, causing increasing fatalities and property damage as the city expands. Engineers and communities need more information on urban landslide drivers such as informal slope cuttings to understand the hazard and identify mitigation measures. However, the detailed topographic data required for such assessments is not shown in existing maps and can be difficult to obtain across wide areas. This study utilized drone systems to perform high resolution topographic surveys at a pixel resolution of 10 centimetres in a typical landslide-prone community. The survey data was processed to create digital terrain models (DTMs) and ortho-photomosaics which were analysed using a geographic information system (GIS) to extract data on land cover, road width, housing structural typologies, and geometries of hundreds of cut slopes associated with informal urban development. These data were analysed and combined with geotechnical data to generate forty-five slope cross-sections representative of the study area. Physics-based slope stability analysis of the cross-sections was carried out using the Combined Hydrology and Stability Model (CHASM). The results quantified the destabilising effect of cutting slopes and allowed critical cut slope angles to be determined. The study demonstrates the effectiveness of drones for obtaining data for urban landslide assessments and allowing the development of high-resolution models useful for physics-based slope stability modelling. This study is relevant for Quito and similar cities where landslide-prone communities are difficult to access.