A Study of Bed Variation at Fall in Rapid Flow River

Abstract

It is well known that the local scour takes place around hydraulic structures such as bridge pier, weir or bed protection works especislly in rapid flow rivers. This phenomena is usually observed after the flood and there exists very few data with respect to the local scour during the flood, which is very important in hydraulic designing works.
Bed elevation during a flood was investigated in order to study the time dependent behavior of the local scour using an automatic riverbed elevation system which are set up along the thalweg downstream of the No.6 and No.7 bed protection works in Toyohira river.
Rapid erosion was observed during the raising stage of the hydrograph, and deposition was observed during the falling stage.
Besides, the result of caliculation by 1-D MacCorrak Method is compared with field data.