城镇化对太湖平原河网的影响——以太湖流域武澄锡虞区为例

为探讨近年来城镇化快速发展等对太湖流域腹部地区平原河网水系的影响，选取城镇化快速发展且城镇化程度很高的武澄锡虞区为例开展了研究。以1960年代、1980年代和2003年水系为基础，依据河道宽度对水系分级，并从河流地貌学角度定量分析了河网密度、水面率、河网复杂度、河网结构稳定度、分维数等结构特征及长时间序列的水位变化。结果表明：研究区水系要素基本上都在减小；不同等级的河流长度和河湖面积除一级河流面积增加外，均呈减少趋势。河网密度、水面率、分维数均变小，河网复杂度、河网结构稳定度下降，河网演化趋于主干化、单一化，河湖连通性下降。城镇化前后变化显著，且1980年代以来变化加快。同时城镇化背景下的水系衰减对河网蓄泄功能也产生了较大影响，使得年平均水位和汛期水位呈现上升趋势，导致洪灾风险增大。故在城镇化过程中应遵循河网演变规律，促进水系的保护

ANALYSIS OF THE URBANIZATION EFFECT ON THE TAIHU PLAIN RIVER NETWORK——A CASE STUDY OF WUCHENGXIYU REGION OF TAIHU BASIN

For its rapid rate and high degree of urbanization,Wuchengxiyu Region is selected as the study area for studying the effect on the plain river system in Taihu hinterland by quick urbanization in recent years.Based on the river system of three periods:1960s,1980s and 2003,the river network is classified into three levels according to the width of channels.Then from the view of river geomorphology,the river structure characteristics,such as the river network density,the water surface rate,the complexity and structure stability of river network,the fractal of river network,are calculated quantitatively,as well as the long-term water level changes.The results show that:1) nearly all the river system features are shorter;2) river length and area of rivers and lakes of different levels are mostly in a decreasing trend except the area of First Level River.The river network density,the water surface rate and fractal dimension of river network all become smaller.Also the complexity and structure stability of river network weaken.The river evolution tends to trunk and single;connectivity of rivers and lakes reduces.There are obvious differences between the conditions of pre-urbanization and post-urbanization.Furthermore,the decrease trend is more obvious since 1980s.In the other hand,the reducing of river system has great impacts on the storage and flood control capacity of rivers,under the condition of urbanization.It makes the annual mean water level and the mean water level in flood season show the increase trend,leading to a high probability of the occurrence and risk of flood.As a result,during the period of urbanization,the rules of river network evolution should be respected to protect the river system and get the aim of making human and river system coexist peacefully.