Slope stability modelling of urbanisation scenarios for communities in north Quito, Ecuador

Quito, Ecuador, is a rapidly expanding multi-hazard environment at increased risk of rainfall-triggered landslides. In such cities, information on the impact of urbanisation on slopes and rainfall intensity-duration thresholds for triggering landslides can be valuable for resilient urban planning. However, rainfall thresholds are usually generated from empirical landslide data, which is often unavailable. This paper presents an overview of recent stochastic landslide modelling work, enabling regional sensitivity analysis and the development of rainfall thresholds based on tens-of-thousands of physics-based slope stability simulations. Typical landslide-prone communities in north Quito are characterised in terms of degree of urbanisation, slope geometry, soil properties and rainfall scenarios. Soil data came from
the new Quito soil geotechnical database and drone mapping successfully resolved slope geometries and more detailed information such as construction materials and slope features. An overview of the modelling methodology is presented. The key findings of the simulation study are that slope cutting, followed by removal of vegetation are the key drivers of slope instability. These findings are discussed in the context of recommendations for land use policy in the studied areas.