Landslide susceptibility assessment based on slope units of mountainous cities and towns: A case study of Kangding city

Susceptibility assessment of geological hazard in mountainous areas plays an important role in geological hazard risk management. Taking Kangding city as the example, nine index factors including elevation, gradient, slope aspect, curvature, engineering geological information, distance to road, distance to rivers, distance to fault zones, and the direction and structure of slope were selected as the evaluation indexes based on slope unit. The critical values were selected from the catastrophe points of the landslide ratio curve and weight of evidence curve to determine the factor states on dividing the entire factors interval and the distance to road was removed because of correlation analysis for each influencing factor. Based on the weight of evidence, the Susceptibility assessment was developed. The method of reduction coefficient was used to evaluate the susceptibility accurately for slope units that already had treatment projects. Combine with field investigation results, the study area was classified into four zones with different levels of landslide susceptibility: landslide extremely high-prone area, landslide high-prone area, landslide moderate-prone area, and landslide low-prone area. The results show that extremely high-prone area were mainly distributed in the Lucheng Town of Kangding City and Erdaqiao village in the north. Meanwhile, high-prone areas were mainly distributed on the side of Yala River, Zheduo River, and Wasi Valley. After the reduction of the slope unit where the treatment projects are located, the area and landslide ratio of extremely high-prone areas decreased from 11.21% to 8.42% and from 4.03 to 2.3 respectively. The research results were in good agreement with the distribution of known landslides, and the accuracy of the assessment is about 77.8%. The landslide susceptibility assessment results obtained in this paper reflect the distribution of landslides in the study area, providing technical support for the refined risk assessment of mountainous cities and towns.