16世纪末以来北运河水系演变及驱动因素

The Evolution and Driving Factors of the North Canal System Since the End of the 16th Century

在对河流水系演变与人类社会发展关系进行归纳总结的基础上,基于历史文献和数字高程模型数据,提取16世纪末至今北运河流域水系4个年份断面(1582年、1820年、1933年和2011年)。同时确定河网分级、进行水文分析,计算水系结构参数。结果表明,16世纪末至今,北运河流域范围逐步缩小,水系格局由亚树枝状向混合状形态演变。1582—1820年是河流长度发育、河流数量、支流发育系数与河网复杂度增加最为显著的阶段,反映了河流主干化的趋势,人类对河流连续性干扰较深。而洪涝引起的水系变动以及人类增加水源、开挖引河、筑堤坝等活动,是水系结构改变的主要原因。

In this paper,based on the summary of the relationship between the evolution of river systems and the development of human society,historical archives and the Digital Elevation Model(DEM)of North Canal Basin(NCB),we used digitizing methods to extract four geographic profiles of the river system in NCB,from the late 16 th century to the present(1582 s,1820 s,1933 s,2011 s).Meanwhile,based on DEM data,we utilized river network classification and hydrologic analysis methods to calculate river system structure parameters.The results showed that from the late 16 th century to now,the range of the basin was shrinking gradually,and the pattern of the river network from sub-dendritic shape was changing to mixed morphology.During A.D.1582-A.D.1820,which was the significant period in which River diversity(R_(d)),River frequency(R_(f)),Tributary development coefficient(T),and river network complexity(CR)increased significantly.Then,the overall trend stabilized,indicating the stream structure became simpler and simpler.By comparing the past river with the present one,we find that the Continuity index(C)of the North Canal has decreased since the Ming and Qing dynasties,indicating that human have imposed deep interference in the continuity of the river.By combining historical documents and DEM data,we find that under the constraints of natural geographical conditions,human excavation of river diversion,building dams,increasing water source to ensure the operation of the canal system and coping with floods,water system changes caused by floods are the reasons for the changes in the river system structure.