Comprehensive risk mapping and management of rainfall-induced slope failures in urbanizing subtropical regions

Geological disasters, such as landslides, collapses, and rockfalls, are significant hazards in humid subtropical regions, especially in rapidly urbanizing areas with intense monsoonal rainfall. This study focuses on Zhongxin Town in northern Guangdong, where fragile geomorphic conditions, exacerbated by urban expansion and human-modified slopes, heighten the risk of rainfall-induced slope failures. Using an integrated multi-parameter risk assessment framework, we combine unmanned aerial vehicle (UAV) data, geographic information system (GIS)-based spatial modeling, field surveys, and hydrometeorological analysis to quantify slope failure susceptibility, hazard, vulnerability, and risk. The susceptibility analysis, based on ten geomorphological, geological, and anthropogenic conditioning factors, shows that only a very small proportion of the area is classified as high susceptibility, while the vast majority falls into low-to-moderate susceptibility classes. Under three rainfall scenarios (100 mm/24 h, 250 mm/24 h, and 240 mm/72 h), hazard zoning indicates that high and extremely high hazard zones are strongly concentrated in steep, human-modified slopes. Vulnerability mapping highlights densely populated village clusters and critical infrastructure as the most exposed elements at risk. Integrating hazard and vulnerability demonstrates that high and extremely high risk zones are confined to a limited number of slope-cut villages, which are prioritized as key prevention and control areas in the final risk zoning. The results underscore the dominant role of cut-slope height and observed signs of damage, together accounting for more than half of the total susceptibility weight, and confirm that rainfall intensity and duration critically modulate hazard levels. By linking fine-scale spatial modeling with practical recommendations, such as slope stabilization, drainage control, stricter regulation of slope-cut construction, enhanced rainfall monitoring, and community-based early warning, this study provides an operational framework for township-scale risk governance and climate-resilient urban-rural development in subtropical southern China.