A Study On The Rationality Of Build-Up Area Of Nanjing City

In the process of rapid urbanization, the quantity of cities has increased sharply and the build-up area of cities expanded at the same time. The conflicts between people and land and the competition between construction land and agricultural land have become increasingly serious, which led to stricter control of the growth of urban land. Effective measures have been taken to limit urban sprawl and to protect farmland effectively. Therefore it’s important to study the rationality of build-up land area for the aim of controlling over-expansion of build-up land and formulating urban planning.Firstly, the research background and the significance were introduced, followed by the description of the main research content, methods and measures used. Secondly, the concepts related with the study were explained and the theory elaborated before the review on corresponding research studies home and abroad. In the Empirical Study of Nanjing City, the spatial-temporal characteristics of the variation of build-up land area were analyzed. Based on the analysis of driving factors of urban expansion, the index system for evaluating the rationality of urban land scale was structured, which consisted of indicators from economic, social and ecological fields. The weight of indicators was determined by entropy method and the evaluation model was constructed by multi-objective functions. Then the rationality of urban land expansion in Nanjing during the period from1990to2007was evaluated, the trend of evaluation results was analyzed and the relative characteristics summarized. According to the economic, social and ecological objectives suggested by the urban plan from2007to2030, the value of each indices were predicted for the rationality evaluation of the planning period. The assessment results could also be used to test the potential rationality of the new round of urban plan. Finally, the conclusions were stated and several items for further study were discussed.The main conclusions included:(1) the study period from1990to2007could be divided into two sub-periods. Period1990-2000differed from Period2001-2007in that the build-up area was adjusted slightly in the first period but increased sharply in the second period. In the1st period, the rationality of urban land-scale declined in spite of the trivial fluctuation caused by slight expansion. The decline of rationality reflected the impediment of limited build-up land area on the coordinated development of economy, society and ecology. The2nd period witnessed the rapid expansion of build-up land area. Although the value of rational evaluation declined at the beginning of expansion, it increased year by year after that, which indicated that the land scale became more reasonable.(2) Evaluation on the rationality of the land scale suggested by the new round of urban plan showed that the rationality increased till2019and then decreased. Increasing rationality before2019demonstrated the feasibility of the urban plan, but after that the negative influences of the limitation of build-up area on the economy, society and ecology would gradually manifest, which proved the necessity of another new round of urban plan.