Susceptibility and risk assessment of earthquake-induced landslides based on Landslide Response Units in the Subao River basin, China

Generally, pixels are the basic unit for assessment of landslide susceptibility. However, even if the results facilitate the comparison, a pixel-based analysis does not clearly illustrate the distribution relationships. To eliminate this deficiency, the concept of the Landslide Response Unit (LRU) is proposed in this study, for which adjacent pixels that have similar properties are combined as a basic unit for susceptibility assessment. The Subao River basin, seriously impacted by the Wenchuan Earthquake, was selected as the study area, and three factors including slope gradient, slope aspect, and slope shape, which have a significant impact on landslides, were chosen to divide the basin into 25,984 LRUs. Then topographic, geologic, and distance factors were applied for the landslide susceptibility evaluation. The logistic regression method was used to establish the susceptibility assessing model by analyzing 2,000 susceptible LRUs and 2,000 un-susceptible LRUs. The model accuracy was defined in terms of the ROC curve value and the κ value, 0.531 and 0.84, respectively. The susceptibility of landslides was divided into low, moderate, high, and very high in Subao River basin, and 73% of historical landslides and all four new landslides are in the highly susceptible zone and very highly susceptible zones. Finally, the LRUs with houses, farmlands, and roads prone to sliding and burial hazard were assessed separately. On the basis of considering the potential movement directions of the LRUs, the result found that 1,001 and 835 LRUs probably would be destroyed by slope sliding and landslide burial, respectively.