The Analysis On Urban Expansion And The Driving Factors Of Lanzhou

City is the most strong regional interaction between human and nature,is a highly integrated complex systems which contains population,resources,information and social economy.With the development of social economy,the city also got unprecedented development.The development of the city includes not only the increase of urban population,the development of economy,the transformation of function,more intuitive is the expansion of urban city scale,the urban expansion.Urban expansion is an important content of urban studies,it reflects the change of the urban scale and shape in space and the conversion between different urban land,is intuitive to reflect the urbanization process.Through the analysis of urban expansion,we can grasp the change characteristics and regularity of urban development,and provide decision-making basis for scientific development of cities.City fringe area is the most sensitive area of urban expansion,also the hotspots of urban geography research,so urban expansion research should first urban boundary information extracted from the beginning.This paper is based on the project of Monitoring the Geographical condition of Gansu Province-“Dynamic monitoring of historical change and urban expansion in Lanzhou city”,taking the Lanzhou valley basin as a study area,and the long sequence,multitemporal,high resolution remote sensing images,aerial images and the large scale topographic map data as the data source,and GIS software as extraction and analysis method,to summary the space-time characteristics and driving factors of urban expansion in Lanzhou city from different angles.This article first reviewed the history of research on urban expansion,on the use of the theory and method of model are summarized and reviewed in this paper.This paper reviewed the history of research on urban expansion firstly,and summarized and reviewed the theoretical methods and mathematical models.Secondly,Analyzing the spatio-temporal process and law of urban expansion from the topic of the extension strength,spatial changes,shape and pattern as well as the rationality of the urban expansion on the basis of multi-period urban boundary information which extracted from remote sensing images and topographic map data.Finally,discussed the drive mechanism which the influence of expansion of Lanzhou city using the social and economic statistical data and the method of the stepwise regression,grey relational analysis and qualitative analysis.Themain conclusions are as follows:1.The Lanzhou city scale expanded gradually last 54 years,the urban area increased from51.66km2 to 142.7km2,rise nearly 2 times and the increase spped is 1.69km2/a,the average annual growth rate is 1.9%.The extension stage presents the early slow spread type-fast winding expand type after The Western Development-great leap forward during The 12 th Five-Year Plan period.2.The Spatial difference of urban expansion is obviously,the urban extended from good condition area to the slope,the suburban terrace,he "overflow" effects of expansion in Lanzhou is obviously.The largest urban expansion area in lanzhou mainly concentrated in the Donggang-Yantan area,three beach area,the industrial zone in west of the Liujiaping of Anning district,Shajingyi,Chenguanying in Xigu district,Pengjiaping-Dongdaping in qilihe district.The main extension direction in Lanzhou is the west,northwest and the next is east,while the minimum extension direction is south and southwest,and the next is east.The speed of expansion to the basin has a rapid growth,82% of the valley basins had been fully urbanized by2015,meanwhile the built-up area of the valley basin has accounted for 6.7% of the total area of the built-up area.3.The boundary shape of Lanzhou tend to be more complicated,and the urban expansion mode is mainly based on filling expansion,while edge expansion is secondary,and present the extended mode of compact and epitaxial alternation.The structure of Lanzhou city changed gradually from polycentric organization at the early stage of the research to the single center which take the Yellow River(road)as the axis,the urban patch fragmentation reduced,and the internal pore decrescented,urban internal contact was further improved.4.The expansion speed of Lanzhou city is much lower than population increase at the beginning of the study,the urban development is slow,the urban expansion speed is much higher than the population growth since 2000,the coordination between urban area growth and population growth was decreasing.5.The major driving factors of urban expansion in lanzhou city are the policy and city planning,the population,industry structure and transportation factors have the greatest impact among social economic factors.The geographical environment factors is the background of urban expansion restrict the extension of the city to some extent.The policy factors was dominated in the planned economy period,followed by social economic factors;The social economic factors gradually become the dominant factors of urban expansion while government policy have begun to play secondary roles in market economy period.