Risk Assessment of Geological Disasters Based on Slope Units in Town Scale A case study of Dazhou Town along the Yangtze River

With the rapid urbanization, the geological disaster risk has attracted increasing attention in the safety risk of town construction. This paper proposes a six-step technical framework for geological disaster risk evaluation in town,i.e.,slope unit division, rainfall condition analysis,automatic extraction of disaster-bearing bodies,hazard evaluation, quantitative evaluation of vulnerability, and risk evaluation.The migrant town along the Yangtze River,Dazhou Town in Wanzhou District of Chongqing,is selected as the study area.An improved hydrological analysis method for multi-scale division of slopes is proposed,which can be employed to extract the evaluation units for geological disaster risk.Based on the fifty-year rainfall conditions through the Gumbel distribution,the limit equilibrium method is adopted to estimate the stability and occurrence probability of slopes.Furthermore,the object-oriented approach is utilized to quickly extract information about buildings and traffic roads,etc.Finally,the hazard evaluation model and the vulnerability evaluation model are established to achieve the risk evaluation of geological disasters in towns,which are based on the slope unit and hazard sourceanalysis, respectively.According to the risk map34.5×103 m2 of buildings and 15.0×103 m2 of roads are in the extremely high risky zone, while about 36.3×103 m2 of buildings and 38.3×103 m2 of roads are in the high risky zone.