本文主要通过曲流模型试验复演曲流过程和分析曲流形成的一些外部条件。着重讨论河谷儿何原始状态、流量变幅和频率、泥沙运动特性及侵蚀基准面变化等因素对形成弯曲河道的影响。

Mmovement track of a unit water body in nature is always winding. It is a natural character of water movement and an internal condition to form the meanders in rivers.Initial shape of a valley,amplitude and frequency of discharge change,mechanism of sediment transportation in rivers and change of basic level of erosion are all important factors influencing meander development.Analysis of the test data of natural models shows that vertical slope of valley,too large or too small,can not make rivers to form meanders.Small transverse slope widen easily river width,favourable to development of branched channel.By contrast,large transverse slope limits width of meander belt,unfavourable to meander development.So does the amplitide of discharge change,if the amplitide is over large,derivation of thalweg track between flood and dry seasons is too large, if over small,the point bar grows slowly,both of them can not get favourable conditions for meander development.Descent of basic level of erosion increases vertical slope of rivers,to make rivers to branch.In special geographic conditions whether a river can develop into meandering river depends on suitable combination of influencing factors,instead of single factor.