Development Of A Rapid Evaluation Method For Multi-hazards Assessment Along Roads Based On Decision Tree Approach:a Case Study From China

Once geological hazards occur along the transport lines,they may cause many serious problems,not only including death and or injuries of passengers but also causing traffic interruption and high repair costs to the transport infrastructure.In order to prevent the occurrences of hazards,it is necessary to take some mitigation measures in the hazardous locations.However,direct and rapid evaluation methods for multi-hazards assessment along roads are relatively limited,and most hazard assessment approaches largely depend on historical inventories.If there is lacking sufficient historical or detailed thematic data,it will be hard to achieve the goal of rapid or emergent assessment.Hence,it is necessary to develop a simple,rapid but effective evaluation method for multi-hazards assessment along road networks.Under the support of ChiGIM Program,this thesis has conducted a special study on the method of rapid geological hazards identification along roadways.The main contents of this thesis are illustrated as follows:(1)According to the characteristics of hazards along transportation networks,six input parameters were used to identify homogeneous road sections,that is,evidence of past events,terrain parameters,land use,remedial works,road infrastructure types and hydrological characteristics.(2)On the basis of field investigation and the multi-temporal satellite images from Google Earth,different decision tree approaches were designed to assess the activity of hazards.Meanwhile,five contributing factors(topography,geological,slope materials,land use and the drainage factors)were taken into consideration and were integrated into a decision tree method systematically.Then a hazard matrix method was used to determine the hazard level based on the results obtained from hazard activity decision tree and favourable condition decision tree.(3)Using the protection efficiency decision method to evaluate the protection state(no protection,destroyed protection,insufficient protection and sufficient protection),the final prioritization class is determined by the combination of the hazard class and protection state.(4)In order to evaluate the efficiency and the reproducibility of this method,it was tested during the field work and in the office using the video images and other data.This method also was applied in two totally different study areas;one is a very active hazardous area while the other has very few landslide hazard problems.Overall,although the proposed method requires expert knowledge to develop the decision tree,the final approach could be used by people who are not experts but have a basic knowledge and awareness about natural hazards,such as local technical persons.It has certain significance for the development of risk management and reduction.