Remote Sensing Image Based Study on the Spatial Evolvement and Mechanism of Urban Residential District in China Since 1949: A Case Study of the Valley-basin City, Lanzhou

Well located at the geometric center of China, Lanzhou is one of the typical valley-basin cities in the western China. There are mountains alongside and Yellow River wandering through the city. Here we choose Lanzhou built-up area as research object, which ranges from 36deg 00´ N to 36deg 10´ N and 103deg 31´ E to 104deg 00´ E. The study area includes four districts (Chengguan, Qilihe, Anning, and Xigu) of Lanzhou city with total area and population is 227.98 km2 and 1,800,000 respectively. Under the planned economic system, housing is welfare system inside the units, so the residents barely have choices for houses. Therefore, urban residential spatial differentiations mainly lie on units´ ownership, location, economic efficiency, scale, housing system etc. With the establishment of market economic system, the previous welfare system residential model was partly impacted by the durative differentiation and conformity of the urban residential district spatial structure in Lanzhou. The valley-basin shaped city is a kind of special city; we take the Lanzhou city as a case to investigate the urban residential district differentiations, spatial evolvement and mechanism. Furthermore, the article suggests the trend and direction of the urban residential spatial differentiations in Lanzhou in the future.