地理科学 ›› 1984, Vol. 4 ›› Issue (2): 115-124.doi: 10.13249/j.cnki.sgs.1984.02.115

• 论文 • 上一篇    下一篇

不同自然条件下水库下游的河床演变

龚国元   

  1. 中国科学院地理研究所
  • 出版日期:1984-03-20 发布日期:1984-03-20

CHANNEL CHANGE OF LOWER REACHES DOWN RESERVIORS UNDER VARIOUS NATURAL CONDITIONS

Gong Guoyuan   

  1. Institute of Geography, Academia Sinica
  • Online:1984-03-20 Published:1984-03-20

摘要: 水库一般有三种不同的运用方式,即滞洪式、非汛期泄空式和蓄水式。同一水库在不同时期其运用方式还可能有所不同。前两种方式主要是为了防洪,而河道仍然保持着天然河流的特点,不会发生河型上的转化,后一种运用方式,一方面改变了上游来水来沙的自然过程,另一方面又受下游区域自然条件的影响,促使下游河道发生巨大的变化,河型上产生转化。近年来为了探索不同自然条件对库下游河床演变的影响,我们对汉江、老哈河水库下游河道进行了实地考察,分析了其它库下游河道的有关资料。

Abstract: This paper analyses channel changes of the lower reaches down reserviors and the transformations of river pattern.These rivers flow through different areas with various backgrounds and natural environments. The characteristics of channel changes under different natural conditions are.(1)The more the released discharge,the longer duration the flow and the further from the dam the erosional base level,then the longer the scour distance is;the more the discharge and the finer the material,the more intensive the scour is.(2)Three situations of channel change exist in longitudinal direction: (a)A concave or linear profile is associated with the grading of bed material and the unequality of scour over river bed (b)When bed material is composed of uniform medium or fine sand and the bed is equally scoured,the parallel lowering of the bed will occur and the longitudinal profile will inherit its original form.(c)Affeeted by the bedrock and the tributaries with heavy load, the profile will be convex.(3)Three types of transverse evolution are:(a)When both the bank and the bed are less mobile,the released discharge will primaryly cause deep scour and results in a narrowed cross-section and in decrease of width-depth ratio.(b)When the bank is less mobile than the bed,the deep scour will occur prior to the lateral erosion and the width-depth ratio might increase.(c)When both the bank and the bed are composed of uniform loose material,the deep scour and the lateral erosion will parallelly operate and less change will occur in the width-depth ratio. As far as the river pattern trasformation considered,the shorter the duration of the released flow,the more the regional storm runoff,and the worse the vegetation,then the more difficult the transformation from braided river to other river patterns.In constrast,the longer the duration of flow,the less the sediment load from the basin and the better the Vegetation,then the easier the evolution of a braided river to a single meandering river is.constrainted by the boundary conditions,these rivers may changed into a confined meandering or stable islandtype river.