河谷盆地型城市扩张的时空与驱动力分析——以兰州市为例

城市建成区扩张是地区城市化水平的重要标志.基于兰州市Landsat系列卫星遥感影像,首先基于提出的多分类器组合土地利用/覆被分类方法,提取建成区范围;其次计算2003—2019年城市扩张速度、扩张强度和城市紧凑度等,分析兰州市建成区扩张的时空特征;最后分析驱动城市扩张的自然条件和社会经济因素.结果表明:①基于分层策略的多分类器组合分类方法对兰州市土地利用/覆被分类效果很好,提取的建成区范围面积与年鉴统计数据也基本一致;②城市建成区面积在16年内持续增加,年增加量6.72 km2,处于快速扩张状态,城市紧凑度较低,扩张合理性差;③由于兰州市"两山夹一川"的自然条件,城市南北方向扩张已趋于饱和,扩张只能沿黄河东西方向;④人口增长和经济的快速发展是兰州市城市扩张的主要驱动力.

Analysis on the Spatial-temporal Characteristics and Driving Forces of the Expansion of Valley-basin Citiy: Takeing Lanzhou as an Example

The expansion of urban built-up area is an important index of regional urbanization level. Based on Landsat series satellite remote sensing images of Lanzhou city, the multi-classifier combination method was adopted to classify land use/cover and extract the range of built-up area. This paper calculates the expansion speed,intensity, compactness and other indexes of the built-up area from 2003 to 2019. The spatial and temporal characteristics of urban sprawl in Lanzhou are analyzed and the natural conditions and economic factors driving urban sprawl are analyzed. The results show that the multi-classifier combination classification method based on the stratification strategy has a good effect on the land use/cover classification in Lanzhou city and the extracted built-up area is basically consistent with the yearbook statistical data. The urban built-up area continues to increase in 16 years with an annual increase of 6.72km², which is a state of rapid expansion. City compact degree is low and expansion rationality is poor. Due to the natural condition of "two mountains with one river" in Lanzhou, the north-south direction of the city expansion tends to be saturated and now it is mainly expanding along the Yellow River in the east-west direction. Through the analysis of social statistics, it is concluded that the rapid development of population and economy is the main driving force of urban expansion in Lanzhou.