Urban expansion and its driving forces based onremote sensed data and GIS:A case study of Hangzhou city from 1991 to 2008

Based on multi-temporal Landsat TM/ETM+ Images and GIS,we extracted information of urban construction land use in Hangzhou with supervised classification and overlay technology.The characteristics of the changes of urban construction land use were analyzed with the aid of spatial overlay technique in order to obtain urban spatial expansion information.Then,the intensity index,direction of urban expansion as well as the situation of the land occupied by urban expansion are analyzed quantitatively,and the socioeconomic driving forces factor and their effect mechanism during the last 15 years(1991 to 2008) were explained.The result revealed that the rate of urban expansion in Hangzhou city was very quick and the urban land area in 2008 was over twice more than that in 1991.The arable land around the urban area,water body and woodland,the main land use types due to the urban expansion,accounted for 66.98%,17.71% and 15.31% respectively.The study also showed that the main human driving forces causing urban expansion in Hangzhou in the past 15 years included the following aspects: the high-speed economic development,the rapid growth of population,the increase of investment at home and abroad,the quick renewal in the old city and the development of suburban real estate,the group development of Higher Education and Science and Technology Development Zone,and the development of urban transport facilities such as the four bridges across the Qiantang River and the two ringed highways around the Hangzhou city.The local government ought to rethink profoundly the advantages and disadvantages of urban expansion in the different stages,and to do in-depth analyses of the future urban expansion mechanism to push forward sustainable urban expansion.