中文摘要：

不透水表面的发展是城市化进程的重要体现。采用天水市1996、2001、2007年3个时期的LandsatTM遥感影像，使用面向对象的方法，通过构建具有较强适应性的比值不透水表面指数RISI，结合植被指数NDVI、水体指数MNDWl等，从遥感影像中提取了不透水面信息，并对其时空发展变化和驱动力进行了分析。结果表明，天水市不透水表面增加明显，与该地区的自然地理格局和经济社会发展密切相关。

英文摘要：

Impervious surface is an important indicator to present the process of urbanization. This study monitored the dynamics of impervious surface in Tianshui city during 1996 to 2007 by using Landsat TM images in 1996, 2001 and 2007 with object based image analysis （OBIA）. This paper, building the Ratio Impervious Surface Index （RISI） and combining Normalized Difference Vegetation Index （NDVI） and Modified Normalized Difference Water Index （MNDWI） for characterizing the urban landscape structure in remote sensing images, analyzed temporal- spatial changes of impervious surface on Tianshui city, The results showed that the area of impervious surface in Tianshui City has increased significantly which is closely related to the geographic structures and social economic conditions.