Spatial-Temporal Changes Of Impervious Surfaces In Resource-Exhausted City

The large-scale expansion of urban impervious surfaces have had an important impact on the urban ecological environment in the process of urbanization,which result in the insufficient supply of groundwater,heat island effect and the carbon island effect.The rapid and accurate acquisition of urban impervious surfaces area from long-term sequence remote sensing images are helpful for reflecting the urban development pattern and the trend of urban impervious surfaces expansion,which is of great significance to environmental management,urban planning and regional sustainable development.In this paper,based on Landsat series data and statistical yearbook data,various methods and techniques such as remote sensing,geographic information system,mathematical statistics were used to extract the impervious surfaces of Tongchuan City in 1986,1991,1996,2002,2007,2012,2017.Finally,the trend of urban expansion were analyzed and the factors of affecting the spatial change of the impervious surfaces were discussed.The specific research results are as follows:(1)The decision tree classification model method is used to extract the impervious surfaces of Tongchuan City by combining Biophysical Composition Index and Modified Bare Soil Index.The correlation analysis method in mathematical statistics is used to verify the accuracy of the extraction of impervious surfaces.The results show that the research method has good applicability to extract the impervious surfaces in the study area,and the accuracy verification method adopted in this paper is convenient and efficient.(2)Based on seven period remote sensing data,the results of extraction of impervious surfaces in Tongchuan City for 31 years are analyzed.The overall distribution characteristics of impervious surfaces in Tongchuan City present a form of "two districts and one corridor"belt group,the direction of urban development is "expansion in the south and west,evacuation in the north and control in the middle.“The urban construction of the northern urban area developed along the Qishui River and Wangjia River,the urban spatial form is in the shape of a“Y”.The residents of the old urban area move southward and westward,the new district as the main center,which of urban space is expanding rapidly in sheet form.(3)According to the analysis of the expansion area of Tongchuan impervious surfaces,we can see that the growth of Tongchuan impervious surfaces reached 55.85 kM2 in 31 years,and the city is in a state of continuous expansion.From 1986 to 2007,the area of urban impervious surfaces at 17.15 kl2,accounting for 30.7%of the total area of urban expansion in 31 years,the expansion speed was slower,and the expansion area was mostly located in the north urban area.From 2007 to 2017,the expansion speed of urban impervious surfaces was at a high level,with the expansion area reaching 38.7 km2,accounting for 69.3%of the total area of urban expansion in 31 years,the conversion of non-urban land to urban construction land was very high,most of the expanding areas are located in Tongchuan new district.(4)The main factors affecting the expansion and change of impervious surfaces in Tongchuan city are social and economic factors,natural factors and government regulation.Social and economic factors are the core factors affecting urban expansion,through multiple linear stepwise regression,the gross output of tertiary industry,the total population,the per capita purity income of rural residents and the average wage of on-the-job workers in the economic and social factors have a greater impact.Natural factors involve three factors:mineral factors,topography and living environment.topography and natural environment have a certain restraining effect on the spatial layout of Tongchuan city during the transitional period;and the policy has a great impact on the spatial structure of urban development and accelerates the formation of urban spatial layout.Through the study of temporal and spatial changes of impervious surfaces in Tongchuan city,it provides theoretical basis for Tongchuan City's urban planning,ecological construction and environmental management.At the same time,it has certain reference significance for the extraction and analysis of impervious surfaces in other resource-exhausted cities in China.