Representative profile model: a new physically-based model using slope unit for hazard assessment of colluvial landslides at large scale

Physically-based model is an important method for refined assessment of landslide hazard at large scale. The traditional infinite slope model homogenizes the slope’s structure and morphology, discretizing the slope into grid units and neglecting the interactions between different parts of the slope. However, slope units constitute the fundamental elements for stability analysis of natural slopes. Moreover, landslide bodies or slopes prone to landslides exhibit significant spatial heterogeneity. In order to realize the landslide hazard assessment in slope units, this study proposes a physically-based model called representative profile model (RPM). RPM takes the slope unit as the assessment unit and couples the slope surface morphology, Quaternary deposits thickness and ground water level. In order to represent the information of the slope unit within a single cross-section, the elevation range of the slope unit is divided with a uniform interval into some elevation segments. Each segment is assigned the average grid values of its respective elements. Then, a representative profile can be generated, consisting of ground surface, sliding surface, and ground water level. RPM also integrates the slices method and the Monte Carlo method to calculate the failure probability, allowing a physically-based hazard assessment in slope unit at a large scale. This study automates the process of RPM model through secondary development of ArcGIS. RPM model were applied in Tiefeng Township, Chongqing, China. The results validated by ROC curves and field investigation represent good performances, which could provide evidence of the potential of RPM for the landslide hazard assessment at regional scale.