A STUDY ON THE EVOLUTION OF CITY SIZE STRUCTURE OF THE YANGTZE DELTA INTERLOCKING METROPOLITAN AREAS

The Yangtze Delta Interlocking Metropolitan Areas is one of the largest city regions in the world, and the structure of its urban system has had a great change since China has implemented the policy of reform and open door. In recent years, its development has been paid more attention to by the central government, and several plans for the Yangtze Delta have been making. So, it is necessary to do more research on the Yangtze Delta Interlocking Metropolitan Area, a better understanding of the evolution of its city size structure will be helpful for predicting the future growth of city population, optimizing the spatial structure, and give some experience to other city regions. The paper collected the data of urban population from 1984 to 2004 for each city in the Yangtze Delta, and analyzed the characters of the evolution of the urban size structure by analyzing the hierarchical size structure, urban primacy indices, the fractal feature and the spatial evolution. After comparing and calculating the data of urban population, the authors found that the evolution of city size of Yangtze Delta Interlocking Metropolitan Areas could be divided into two phases. The feature of the first phase is the rapid development of middle cities and small cities, the number of the cities increased from 10 to 47 in 2000, and at the same time the population percent of middle and small cities increased from 19.62% to 37.44%; After 2000, the feature of the second phase is the accelerated development of large cities, in four years the number of large cities increased to seven, and the population percent increased from 48.18% to 63.52%. The drive forces in these two phases are also different. The urban development policy, especially the policy of encouraging counties transformed to cities played an important role before 2000, and the number of small and medium sized cities increased. But later under the background of globalization, the mechanism of market economy becomes much stronger. The large cities have obtained more opportunities of development so that number of large cities has increased since 2000. Meanwhile, the spatial pattern of the Yangtze Interlocking Metropolitan Areas has been changing. The traditional spatial pattern mainly shows the difference between the north and the south of the Yangtze Delta, and the Z shaped axes consisted of Nanjing, Shanghai, Hangzhou and Ningbo is the most important development corridor. As the construction of coastal transport channels, these cities locating in the Yangtze Delta will get more opportunities. At last, there will form the spatial pattern consisted of 4 metropolitan regions cored on Shanghai, Nanjing, Hangzhou and Ningbo respectively in the Yangtze Interlocking Metropolitan Areas.