无定河及其各支流的断面水力几何形态

The hydraulic geometry of Wuding River and its tributaries

水力几何形态关系是对河道形态与水力学特征之间的关系进行定量描述的一种重要方法,对于河道整治有着重要的意义。本文以无定河及其支流为研究区域,利用该流域1959～1969年期间的实测流量资料,分析了34个河段的断面水力几何形态指数。结果发现,无定河所有河道的水力几何形态指数总体上可以分为三类:b>f&m>f&b+f>m;b<f&m>f&b+f>m;b<f&m<f&b+f>m。平均河宽与宽深比指数存在着类似的非线性尺度效应,平均水深的指数存在与其截然相反的非线性空间尺度效应;而平均流速指数与流域面积之间不存在明显的相关性。某些站点的水力几何形态关系不遵循幂函数关系,而是呈现较好的自然对数关系或者二次多项式关系。

The hydraulic geometry is an effective tool in quantifying the relationship between channel morphology and hydraulic variables.The research on hydraulic geometry plays an important role in understanding the channel change caused by natural environment change and it can provide some insightful advice in river restoration and channel design.The study area is located in the Wuding River Basin.Using the data measured during the period 1959-1969,the hydraulic geometry relationships are analyzed for 34 cross-sections.The results show that the hydraulic geometry exponents can generally be categorized into three types：b〉f ＆ m〉f ＆ b＋ f〉m;b〈f ＆ m〉f ＆ b＋ f〉m;b〈f ＆ m〈f ＆ b＋ f〉m.There are similar spatial scale effects for both mean width and mean width to depth ratio exponents,and an inverse relationship exists in mean depth relationship.There is no obvious correlation between mean velocity and drainage area.The differences of the hydraulic geometry exponents can be ascribed to different stream orders and channel functions.The streams of lower order originate from eroded areas,where erosion is the dominant process and thus,the channels are relatively shallow.The streams of higher orders are adjusted to transport imposed sediment,so the channels are narrower and deeper.In addition,the hydraulic geometry of some stream channels does not agree with the power function.The natural logarithm relations or quadratic relations may be good alternatives.This probably implies that the channel scour and fill lead to the instability of channel morphology.