重庆主城区建设用地扩展的时空特征及驱动因子分析

ANALYSIS ON SPATIAL-TEMPORAL CHARACTERISTICS AND DRIVING FORCES OF URBAN CONSTRUCTION LAND EXPANSION IN THE METROPOLITAN AREA OF CHONGQING

以多时相的遥感影像为基础，选用归一化裸露指数（NDBI）、重归一植被指数（RDVI）和改进的归一化水体指数（修改后的NDWI），通过阈值分割、掩膜处理提取建设用地信息，结合重庆主城区的社会经济数据，利用扩展速度指数、扩展强度指数、扩展弹性指数、紧凑度指数、建设用地扩展系数及扩展方向分析研究了不同阶段建设用地扩展的时空动态特征，并运用灰色关联分析，对建设用地扩展的驱动因子进行探讨。结果表明：1988～2011年重庆主城区建设用地扩展了393．32km2，扩展速度和扩展强度呈现增大的趋势；扩展弹性系数、建设用地扩展系数波动变化，反映了重庆主城区建设用地逐渐由粗放型向集约型转变；建设用地扩展的空间分析表明重庆主城区的城市形态由非紧凑型向紧凑型发展，同时扩展方向具有明显的分异性，主要向正北和西北方向扩展；人口增长，尤其是城市人口的增长是重庆主城区建设用地扩展最主要的驱动因子；经济发展、产业结构变化与建设用地的扩展也有明显的相关性。

With rapid economic development ,urban sprawl becomes an important feature of urbanization in Chongqing. However, population, environmental and social problems resulted from urban expansion has emerged. In this paper we studied the characteristics and influencing factors of urban expansion in the metropolitan area of Chongqing. Based on the multi-temporal Landsat TM/ETM@ data of 1988,1995, 2000,2002,2007 and 2009, we used normalized difference barren index （NDBI）, re-normalized difference vegetation index （RDVI） and improved normalized difference water index （revised NDWI）, combined with threshold segmentation and mask processing to retrieve information of urban construction lands. The combined use of the three indices has better performance than that of single-band or single-index interpretation. This method using automatic and semi-automatic extraction would be an effective way to identify urban construction lands with high accuracy. Combined with socio-economic data in the metropolitan area of Chongqing,we calculated an expansion speed index, an expansion intensity index, an expansion elastic index, a compactness index, an expansion index of urban construction land and an expanding direction analysis to study spatial-temporal dynamics of urban expansion. The driving forces of urban expansion were analyzed by using Grey relational analysis. The results showed that （1） the area of the urban construction lands expanded by 393.32 km2 from 1988 to 2011, and the expansion presented an accelerated trend. Especially during 2009--201I, the expansion area was 36.67 kme, which accounted for 38.12% of the total extension area during the whole study period. （2） Fluctuations of expansion elastic index and expansion index of urban construction lands indicated a transformation from extensive to intensive expansion. （3） Spatial characteristics of urban expansion showed that the urban areas in Chongqing developed from a non-compact to a compact form. The extending direction showed obvious spatial differentiation,with north and northwest as the main direction. （4） Population growth,especially urban population growth is the main driving force of the expansion of urban construction lands. Economic development and the transformation of the industrial structure also had a significant correlation with the expansion of urban construction land.