Research On Risk Evolution Simulation And Dynamic Management And Control Of PPP Project In Sponge City Based On GTA And SD

Urban flood disaster has become a prominent problem affecting global public security,and has also become an important factor restricting urban economic and social development.With population growth and accelerated urbanization,human activities put more and more pressure on the environment,resulting in frequent floods;And flood disasters in turn seriously endanger people’s production and life.Therefore,the work of flood control and disaster reduction is urgent.With the migration of the urban population and the continuous adjustment of the industrial structure,China also has various serious water ecological problems such as waterlogging,water pollution,and loss of aquatic habitats caused by the rapid development of urbanization.After analyzing and summarizing foreign rainwater management concepts,China has put forward an urban water resource management method that conforms to its own national conditions—sponge city.Subsequently,a large number of sponge city PPP projects were put into construction.However,during the construction process,some problems such as poor construction experience,imperfect quality management system,and weak public awareness were exposed,resulting in the gradual decline of sponge facility construction in some areas.The expected benefits are not ideal,and the enthusiasm of the people is low.In this context,comprehensively and systematically discussing the risk development law of sponge city projects and establishing a scientific and efficient risk sharing mechanism have become the focus of sponge city research.Based on this,the basic scientific research ideas of “theoretical definition-mechanism analysis-model simulation-sharing quantification” are formulated.First,by sorting and summarizing the existing literature,the connotation of sponge city risk is redefined.The grounded theory is used to determine the causes of various risks,and summarize them into five systems: Regulation,management,capital,construction and society,and explore the internal correlation between the various systems.At the same time,in view of the various factors involved in the construction of sponge city,and each factor shows dynamic changes in the overall life cycle.Therefore,the system dynamics method is used to establish the risk evolution model of sponge city PPP project.Taking the construction of sponge city in Huangdao District,Qingdao City as an example,it analyzes the overall risk changes caused by the dynamic changes of various factors in the construction process,as well as the dynamic evolution of various risks in the entire life cycle.However,the research does not stop at the simulation of the qualitative level of risk.It also calculates the risk sharing ratio from the quantitative level,and is committed to solving the risk problem fundamentally.Therefore,through literature research and case data analysis,the bearer of the shared risk factors was firstly clarified.Then,based on the risk control ability,risk-taking willingness,and risk-value identification degree,the analytic hierarchy process and the fuzzy comprehensive evaluation method are applied to determine the proportion of shared risks that the public and private parties need to undertake respectively,so as to obtain a scientific,complete,dynamic risk sharing scheme.Finally,the risk prevention suggestions to mitigate the risks of sponge cities are put forward in a targeted manner.The research conclusions are as follows:(1)Among the five subsystems,management risk has the greatest impact on the overall sponge city,followed by construction risk,both of which need to be paid attention to and guarded against during the construction process;(2)Management risk always develops at a high level throughout the life cycle of the project.But at the beginning of the project,regulatory risk was only briefly at a high level,and the impact of construction risk and social risk was rising.Therefore,risk management control tools and measures should be dynamic;(3)It can be seen from the analysis of the interaction between the subsystems that the management risk has a direct impact on the construction,capital and social risks;(4)In the further sensitivity analysis of risks,the influence of the factors(include“inadequate national policies and laws”,“lack of attention from local governments”,“high operation and maintenance costs”,“improper planning and design”,“public opposition”,etc.)on the construction of sponge city is obvious.In the process of risk prevention,more attention should be paid to the above aspects;(5)There are 8 risks borne by the government(about 35%),8 risks borne by the private sector(about 35%),and 7 risks jointly borne by both parties(about 30%).Overall,the risks borne by the two sides are different,but the number is equal.