基于对Leopold-Wolman关系修正的河床河型判别

Channel Pattern Discrimination Based on the Relationship Between Channel Slope and Width

在广泛收集中国和世界上冲积河流资料的基础上,以近200条河流的大样本对著名的、国际上沿用40余年的Leopold-Wolman关系,即用于河型判别的比降-流量关系进行了检验。结果发现,该关系不能用于包括砾石与砂质河床在内的河型判别。这是由于比降-流量关系主要反映砾石河床与砂质河床之间差异,其次才反映分汊与弯曲河型之间的差异。为此,对于Leopold-Wolman关系进行了改进,提出了以比降和河宽来判别河型的新关系。这一关系综合反映了河流在纵向上的能耗、阻力与输沙特性与在横向上的流场与环流分布特性的组合关系,因而具有更好的河型判别效果,可以用于包括砾石与砂质河床在内的河型判别。

The classic channel slope-discharge relationship proposed by Leopold and Wolman (1957) for channel pattern discrimination has been tested by a large database including 4 types of rivers: gravel-bed meandering, gravel-bed braided, sand-bed meandering and sand-bed braided rivers. The result shows that the Leopold-Wolman relationship cannot discriminate channel patterns well when both gravel- and sand-bed rivers are considered. It is indicated that the Leopold-Wolman relationship reflects the difference between gravel- and sand-bed rivers more than the difference between meandering and braided channel patterns. The channel width-bankfull discharge relationship for discrimination channel patterns of sand-bed rivers in China is also tested in this stud. The result shows that the channel width-discharge relationship discriminates channel patterns better than the slope-discharge relationship. To improve the Leopold-Wolman relationship, a diagram based on the channel slope-bankfull width relationship is proposed. This diagram shows that the slope-width plane is divided by two straight-lines into 4 areas, with each type of river located in each area. Hence, the two straight lines can be regarded as the thresholds between the 4 types of rivers: gravel-bed meandering, gravel-bed braided, sand-bed meandering and the sand-bed braided patternes.