Residential community-based quantitative risk assessment of rainfall-induced loess landslides for the suburban residential areas of Chengguan district in Lanzhou city with an innovative framework

Suburbs of Lanzhou city have been suffering from rainfall-induced loess landslides. In this study, we present a quantitative risk assessment of rainfall-induced loess landslides at residential community (RC) scale for suburbs of Chengguan district in Lanzhou city with an innovative framework. Under the framework, risk components (hazard, elements at risk, their exposure, and potential value affected), hazard subcomponents (landslide probability, magnitude and intensity) were characterized using their descriptors. Each descriptor was quantified using different approaches according to its nature and data availability. This framework innovatively integrates risk components via their intrinsic links, centers on RC-based exposure, and considers urbanization for estimating potential value affected. Landslide probability, described by probability of factor of safety ≤ 1.0, was quantified using a probabilistic mechanism-driven approach. Magnitude and intensity, described by volume/maximum width/source area, runout/area affected, respectively, were quantified using a hybrid mechanism- and data-driven approach. Residents and buildings were treated as elements at risk. Exposure at RC level and potential value affected were estimated through a hybrid mechanism- and a data-driven approach by considering links of risk components, growth of population, building area, and construction cost. The results revealed that 29, 31, and 34 RCs would be affected by landslides under 20-, 50-, and 100-year rainfall intensities, respectively. Total annual risk is estimated at 156 affected residents and building losses worthing 41 million CNY. RCs along the northern slopes of Gaolan Mountain and in Jiuzhou are identified as higher-risk zones. The framework developed in this study can be applicable to other mountainous cities.