SEDIMENT TRANSPORT IN RIGID BED CHANNELS

Abstract

Lined channels are often used in water supply, hydropower systems and irrigation in preference to unlined wallm- CtbkAS channels primarily to minimise seepage losses and arlso for conserving the avila.ble head. Quite often these channels are required to certain amount of sediment load along with the design discharge. Since in these channels there is no problem scour, the design consideration requires that channel dimensions be adequate to carry this load without any deposition on the bed. Not much information is available concerning the sediment transport capacity of rigid bed channel. On the basis of sours, experimental data some empirical relationships for the limiting transport capacity in these channels have been proposed by Novak & Nalluri, Pullaiah, Arora et al, Westrich & Juraschek and Celik & Rodi. These relationships are limited to rectangular and circular channels and do not specifically consider the mode of transport in these channels in relating the transport capacity. Depending on the size of sediment and the available shear, the sediment load in such channels may move as bed load and suspended load. In view of these limitations it was considered desirable to re-examine some of these relations using existing available data. Analysis. of data shows that the limiting sediment concentrations predicted using some of these relationships vary singnificantly. Further in an attempt to consider the effects of channel shape and its boundary roughness, the functional relationship relating limiting sediment concentration with relevant parameters has been proposed for rectangular &. circular channels. The available data supports such a functional relationship. The results of this re-analysis are reported in the present investigation. Aspects that need further examination have also been reported here.