River bed topography in meandering streams and its relationship with local scour

Abstract

In Meandering Streams, deformation in bed topography occurs due to secondary flows. This situation significantly increases the local scour depths around hydraulic structures such as bridge piers and dikes, especially at the central angles of similar to 60 degrees, similar to 130 degrees and outer boundaries of the channel. Therefore, it is important to determine bed topography in dealing with local scour depths around hydraulic structures and investigate its effect on scour depths. In this study, bed deformations generated before the construction of hydraulic structure in a channel bend of 180 degrees due to only flow are investigated. For this purpose, a series of experiments were made and bed topography was obtained by measuring the bed elevations at each central angle of 5 degrees. As a result of the experimantal study, scour was not much observed in the beginning of the meander because the meterials coming from the upstream replaces the carried material, but it was observed that the scour depth increases because of the lack of incoming material. The generated relative flow depths were determined at flow axis and along the line which was thought to be at a distance of 20 % of channel width from the channel boundary and bed topography generated by the effect of flow was obtained. As a result, it was observed that the parameters which are effective in the generation of bed topography due to flow at meandering channel have the same effect in the generation of local scour when an obstacle is placed and that the bed topography and local scour depths have a very close similarity.