CRITERION FOR SEDIMENT DEPOSITION IN RIGID BOUNDARY CHANNELS

Abstract

Over the years unlined and lined channels have been used for taking water for various purposes. Lined channels have obvious advantages over the unlined channels as regards reduction in seepage losses, maintenance costs etc. Laws of sediment transport in alluvial channels are well known but only limited information is available regarding such laws for rigid boundary channels. In spite of the fact that a large number of empirical relationships have been proposed for the limiting bed load and the suspended load transport In these channels, studies have not been made to examine the relative accuracies of these relationships. Available relationship fall Into two broad categories, one for bed load and the other for the suspended load. There is no single relationship which describes these two modes of sediment transport together In predicting the total sediment concentration. Further, at koorkee, data have not been collected for the bed load transport in rigid bed channel though they were available for the suspended toad. This study was thus t:rkr-n up to verify existing re]at.lons for predicting sediment deposition free conditions inrigid bed channels and to collect r,xp(rr-imentnl data for the limiting bed load concentration in rigid bed rectangular channel. The aim was also to explore the possibility of developing a new relationship for total load transport in these channels for different channels shapes. Results of analysis of all the available data are reported in this investigation. It is also seen that the relation based on the stream power concept describes the limiting sediment concentration in these channels. For rectangular channels a relation has been conclusively obtained which relates the total limiting load to the flow and sediment characteristics. For the trapezoidal channel this type of relation with the effect of shape factor has also been obtained. For circular channle a suitable shape parameter could not le obtained.