A model for unsteady sediment transport in degrading alluvial channels

The collection of data for unsteady/non-uniform sediment transport rates in a river below a reservoir, which arrests sediment from upstream, is very difficult. The establishment of a model for the determination of these sediment transport rates is equally difficult but important for the safety of a structure below the reservoirs. An indirect technique based on continuity equation for sediment transport has been used to obtain such data for unsteady/non-uniform flow conditions. Based on these data and dimensional analysis, a relationship for determination of sediment transport rate below high capacity reservoirs under unsteady-non-uniform conditions has been proposed which gave very high efficiency when checked with the available data for such conditions. As a consequence, a relationship for extent of degradation has also been established.