太湖流域城乡用地扩张对河网的空间占用机制初探

The Occupation of River Network by Urban-rural Land Expansion in Taihu Basin,China

城乡景观改变了河网结构的自然演进,致使河流洪水调蓄、生物多样性等功能退化。论文提出基于区域尺度分析城乡用地扩张对河流干扰的空间概念——城乡内河,直接把流域河流集合体的拓扑结构与城乡用地联系起来,并通过城乡内河密度URRD和490个小流域单元,揭示太湖流域城乡发展最快时期用地扩张对河网的空间影响机制：URRD值从1985年的57.10m/km^2增长到2010年的122.28 m/km^2,翻了一番,等级结构由低级主导到高级领先,明显沿重点发展轴线以城镇为核心向四周蔓延,局地呈现负增长;分析表明,URRD与河网密度RD相关弱,与城乡用地密度URD相关显著,但不同URD阶段URRD-URD相关系数不同,即URD 0~15%和25%~40%区段URRD-URD相关最高;通过小流域样本统计与典型样本案例分析,初步揭示城乡内河的分布差异是不同增长阶段新增城乡用地空间增长模式差异（相对河网的位置与集聚性）的结果,由此建议针对不同城乡发展阶段采取保护、防卫、创建等城乡-河流整体协调的空间策略。

Rapid processes of urbanization have altered the natural processes of river network structure in the watershed and led to the degeneration of ecological service functions, such as flooding storage and biodiversity. The paper proposed a new concept of urban- rural river,which links the urban-rural land with the topology structure of the river system, and measured the occupation of river network by the urban- rural land expansion. Urban- rural river are transformed from natural rivers in the watershed enveloped or overlaid by the urban-rural land which alter the natural processes and functions. It can be a spatial feature indicating the impact of urban- rural development on the river network. Based on the urban- rural river density（URRD） and the characteristics of 490 spatial units of sub- basins, the paper measured and revealed the impact of urban- rural development on river structure in the Taihu Basin. The URRD increased from 57.10 m/km^2 in 1985 to 122.28 m/km^2 in 2010, and the leading structure changed from low level to high level. The growth of URDD centered at the cities in the important development belts, such as Shanghai- Nanjing, Shanghai- Hangzhou and along Yangtze River. There was a weak correlation between the URRD and the river density（RD）,and a significant correlation between the URRD and the urban- rural land density（URD）,however, the correlation coefficient was different in different phrases of urban- rural development, such as in the phases of URD 0- 15% and URD 25%- 40% they had the most significant correlation. Based on the statistics of samples in sub- basins and study of typical cases, the changes of the correlation may be linked with the different patterns of urban- rural land growth in different development phrases. The urban- rural river resulted from the urbanrural land expansion in the watershed, and presented a spatial difference in the watershed owing to the growth pattern of urban- rural land, such as infilled growth or intensive growth.Thus, the strategies is proposed to coordinate the spatial patterns of the urban- rural land and river networks, such as protective, defensive and offensive, which can adapt to different development phrases of urban-rural land expansion in the sub-basins.