The Study On The Expansion’ Reasonability Of Urban Built-up Area Based On Regional Analysis Of Land Use And Land Cover Change

As an important part of land resource, urban land is an important carrier of urban’s economy,society, zoology and culture,and with the development of social economy and the acceleration of urbanization,city’s number is increasing constantly and the scale of land use is expanding persistently,which has cause the human-land conflict increasingly prominent. Reality requires human need to implement a dynamic detection on the change of land use and urban land,and take achievable measures to restrict city’s unordered expansion,which can maintain a well land resources structure.Taking Jiangjin district of Chongqing as the object of study,conbining remote sensing and GIS,and taking remote-sensing images of the year 1995,2001,2007 and2013 as data source,and finally conducting a study of dynamic detection on Jiangjin’s land-use change and city’s expansion about 19 years,and then constructing the evaluation indicators system of the reasonability of urban built-up area conbining Jiangjin’s reality,and then doing a evaluation. conclusions are as follows:1.The change of Jiangjin’s land use nearly 19 years is obvious.In terms of quantity,all the six land types(construction land, cultivated land, forest land, water area,unused land and grassland) have varying degrees of change, among these six land types, the area of construction land shows an increasing trend overall,the amount of growth is 10296.96hm2 in ninteen years,and its dynamic degree is highest and is2.60%;The area of cultivated land shows a decreasing trend with different amplitude year by year,and its decreasing amount and dynamic degree are 23972.60hm2 and-0.88% respectively; The area of forest land also shows an increasing trend, and theamount of growth and its dynamic degree is 13772.18hm2 and 0.25% respectively;The water area and grassland’s area show an increasing trend overall,but both of their amplitude of variation aren’t lange;The area of unused land shows a decreasing trend as a whole. In terms of use degree,all the calculated values of land use degree of every year are over 250,which shows Jiangjin’s land use degree is relatively high; In terms of land use structure,the diversity indexs of Jiangjin’s land use structure of every year show an increasing trend,which shows the six land types’ function have gotten full play and Jiangjin’s land use structure is tend to be reasonable.2.The expansion of Jiangjin’s urban built-up area nearly ninteen years is prominent,and development pattern of conglomeration structure is obvious.In ninteen years,Jinagjin’s urban built-up area changes from 253.56hm2 of 1995 into 3202.12hm2 of 2013,and the amount of growth is 2948.56hm2 as a whole.Annual expanding rate,expanding area and expanding intensity index are 8.14%,147.43hm2 and 11.34 respectively,as a whole, Jiangjin’s urban expansion is in a status of high-speed expansion,and the urban built-up area of the three groups(Jijiang group,Degan group and Shuangfu group) all have varying degree of expansion,and all of these groups are in a status of high-speed expansion. The compactness indexs of Jiangjin’s urban built-up area of every year show a decreasing trend year by year,and changing from0.23 of 1995 into 0.02 of 2013;Accordingly,the values of fractal dimension of Jiangjin change from 1.184 of 1995 into 1.266 of 2013 gradually,which shows Jiangjin’s degree of irregularity of urban development becomes higher and higher with the increasing of Jiangjin’s dispersion degree of urban development.In terms of every group,the space of urban development is relatively concentrated in Jijiang group, urban’s compactness is highest,and its degree of irregularity is relatively lower; urban’s compactness of urban development is relatively low in Degan group,and its degree of irregularity is relatively high;The urban’s compactness of Shuangfu group is lowest and its degree of irregularity is highest.3.Building Jiangjin’s evaluation indicator system of the reasonability of Jiangjin’s expansion of built-up area.Taking “comprehensiveness- all-sideness- effectiveness” as construction idea, under the guidance of the principles of science, comprehensiveness,feasibility and independence and under the basic of existing research,and conbining Jiangjin’s developmental practice and finally building the evaluation indicator system of the reasonability of Jiangjin,and this evaluation index system includes three subsystem:the first one is evaluation system of the scale of urban land,whicn includesfive indicators that are used to evaluate the reasonability of the scale of urban land; the second one is evaluation system of the efficiency of urban land,whicn includes eight indicators that are used to evaluate the reasonability of the efficiency of urban land; the third one is evaluation system of urban’s layout-morphology,whicn includes two indicators that are used to evaluate the reasonability of urban’s layout-morphology.4. The reasonability of Jiangjin’s expansion of built-up area gets enhanced.From the evaluation results,the indexs of the scale of urban land in Jiangjin show a steadily increasing trend year by year,and increases from 0.000 of 1995 to 0.321 of 2013;Similarly, the indexs of efficiency of urban land in Jiangjin show a constantly increasing trend year by year,and increase from 0.038 of 1995 to 0.571 of 2013,and the value of 2013 is forteen point zero three times of the value of 1995. The indexs of urban’s layout-morphology show a constantly decreasing trend,and the values decrease from 0.107 of 1995 to 0.000 of 2013;In terms of comprehensive index,the values show a constantly increasing trend from 1995 to 2013 of Jiangjin,and increase from 0.145 of 1995 to 0.892 of 2013,and the index has increased five point fifteen times.As a whole,Jiangjin’s expansion of urban built-up area conforms with the need of land for economic development,and its reasonability of expansion gets enhanced gradually.