Study On The Evolution Of Changsha Urban Water System And Its Influencing Factors In The Process Of Urbanization

Urban water system is the main carrier of urban water resources and an important part of urban ecological environment.In the process of rapid urbanization,a large number of urban water systems have been subjected to a series of artificial interventions such as filling,re-channeling,merging,cutting and straightening,which have seriously affected the shape and quality of urban water systems,resulting in a significant reduction of the flood and disaster prevention capacity of urban water systems and a serious imbalance of the ecological structure of water resources.Therefore,it is necessary to summarize the evolution of urban water system during the urbanization process,clarify the factors influencing the evolution of urban water system,and provide scientific basis for urban water resources protection,land allocation planning,spatial structure adjustment and urbanization construction.The paper takes the urban water system in the main urban area of Changsha from 1995 to 2020 as the research object.On the basis of analyzing and summarizing the relevant studies on the evolution of urban water system,the research framework of the evolution of urban water system in the urbanization process is constructed in four dimensions:space,quantity,structure and connectivity,and the evolution characteristics of urban water system in Changsha in the urbanization process are summarized through the analysis of specific water system characteristic parameters.Then,the factors influencing the evolution of urban water system in urbanization process were identified by using gray correlation degree,and the future evolution trend of urban water system was predicted by using gray GM(1,1)model.Finally,corresponding conservation optimization strategies are proposed based on the research results.The main research contents are as follows:(1)Based on land use data and historical map data,an urban land database of the main urban area of Changsha from 1995 to 2020 was established,and the transfer of urban water system from 1995 to 2020 was analyzed by using the land transfer matrix to observe the relative position relationship between the center of gravity of water system and the center of gravity of urban land,and to identify the high incidence areas of urban water system transfer events.Then,the evolution trend of urban water system in three dimensions of quantitative characteristics,structural characteristics,and connectivity characteristics in the study area from 1995 to 2020 was analyzed by eight water system characteristics parameters:water surface rate,river network density,river frequency,river network complexity,river network development coefficient,water system circularity,node connectivity rate,and hydrological connectivity,so as to characterize the evolution of urban water system in the main urban area of Changsha city during urbanization process To identify the problems of the urban water system at this stage.(2)The evolution of the water system in the main urban area of Changsha City from 1995 to 2020 was counted,and the direct causes of these events were identified qualitatively.Subsequently,the urbanization index system was constructed based on the qualitative identification results in seven aspects:climate,population,economy,industry,life,water resources and land use.The degree of correlation between urbanization indicators and urban water system characteristics parameters was analyzed by using gray correlation,and then different types of urban factors were ranked in order of their influence on the evolution of urban water system,so as to identify the main driving factors of urban water system evolution.A gray GM(1,1)model is used to predict the evolution of the quantitative,structural and connectivity characteristics of the urban water system in the main urban area of Changsha in the next 25 years,and to clarify the evolution of the urban water system in the future under the existing development environment.(3)Based on the study of the evolution trend of the urban water system in the main urban area of Changsha from 1995 to 2020 and the influencing factors,the optimization strategies for the protection of the water system in the main urban area of Changsha are proposed in four aspects:improving the characteristics of the urban water system,reasonably guiding the urban layout,promoting the water system-industry combination,and the synergistic development of blue-green ecological space,in order to provide a scientific basis for the future urban development planning and the protection and utilization of the water system.