Abstract:
Background Affected by typhoon "Du Suri", from late July to early August 2023, heavy rainfall in the Beijing-Tianjin-Hebei region led to many landslide disasters in Mentougou district (MD), southwest of Beijing. At present, there has been no study on the disaster mechanism of landslides during heavy rainfall in North China, represented by Beijing. Therefore, exploring the spatial differentiation pattern and underlying influencing mechanisms of the landslide in MD holds utmost significance. Such an analysis offers a scientific foundation for the Beijing mountain area to effectively respond to landslide disasters triggered by heavy rainfall, thereby playing a crucial role in mitigating the risk of local soil erosion.
Methods Utilizing pre-disaster and post-disaster satellite imagery along with auxiliary data, the landslide information was meticulously extracted. The general distribution characteristics of landslides caused by heavy rainfall were analyzed from a macro point of view. And then, the mechanism of the spatial differentiation of landslides in MD was explored further by statistical analysis and coefficient of variation using the digital elevation model (DEM), land cover and fraction vegetation coverage (FVC) data.
Results It was found that a staggering 5 680 landslides (> 100 m2) occurred during the disaster, cumulatively affecting over 5.85 km2 of land in MD. Notably, the spatial distribution of these landslides demonstrated strong clustering patterns. In this disaster, many large landslides were distributed along the upper reaches of the Yongding River, and some of small landslides occurred from the upper reaches of the Ciwei River to the lower reaches of the Yongding River. Further investigation delved into the spatial differentiation mechanisms of these landslides. While the intense rainfall played a key role in triggering this widespread disaster, factors such as topographic slope, FVC, and land cover significantly influenced the severity of landslides. Three key findings emerged from our analysis: 1) As slope increased, both the density and average area of landslides rose, and the variability in landslide size decreased gradually. 2) Higher vegetation coverage translated to a decrease in both the density and average size of landslide. 3) The disturbance of land surface also influenced the severity of landslides. Areas subjected to greater anthropogenic alteration, such as bare land and farmland, tended to experience larger landslides compared to areas dominated by natural vegetation, particularly forests.
Conclusions This study shows that topographic slope, vegetation coverage and human disturbance have important effects on the spatial differentiation characteristics of landslide hazards though rainfall is the direct cause of large-scale landslides in the study area. Landslide disasters caused by heavy rainfall are rare in Beijing. The spatial differentiation analysis of landslide caused by "23·7" flood in MD may improve the understanding of the mechanism of landslide in Beijing. Therefore, the results will provide a scientific basis for the construction of disaster prevention and reduction projects and post-disaster recovery and reconstruction in North China, represented by Beijing.