Author(s): M. Michiue; O. Hinokidani

Linked Author(s):

Keywords: No Keywords

Abstract: When a bridge is constructed across a river channel,we should oftenconstruct a artificial contraction.In such case,even if sediment dischargein the river is in balance and the bed variation does not occur at up-anddownstream region of the contraction,the river bed variation may occur at thecontraction during flood. There are several patterns for river bed variations.The river variationof the large scale is occurred by changing the boundary condition of the riverchannel,such as the construction of a big dam and on the other hand,the sandwave is a smallest one affected with sand diameter or water depth.The riverbed variation at the contraction during flood which is presented in this paper,is caused by the temporary and longitudinal nonequilibrium condition of sedimentdischarge which is related to the unsteadiness of the flow and the existence ofthe contraction. So its characteristics will be affected by the relativerelationship between the phase of flow and river bed variation.Especially,itis very interested that firstly the bed degradation will occur at the risingstage during the flood,and then the phenomenon of bed aggradation may occur atthe falling stage.In this paper,the characteristics of river bed variation at contractionduring flood are investigated experimentally.Moreover its characteristics fornatural river which have several types of contraction are also investigated bythe numerical simulations on the basis of one dimensional bed variation method.

DOI:

Year: 1989