Author(s): K. G. Ranga Raju.

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Abstract: Eversince the early work of duBoys on bed loadtransport,engineers have been striving to evolvemethods which would enable calculation of sedimenttransport rates to a reasonable degree of accuracy.It is perhaps an indication of the complexity ofthe problem that even today one tends to regarda method as a good one if the actual loads are anywherebetween one-half and twice the computed values!Reservoir sedimentation rates and morphologicalchanges in rivers brought about by execution ofriver improvement works are strongly dependenton the rate of sediment transport and the continuingendeavour for a more accurate sediment transportlaw is thus understandable.Even the relatively simplecase of transport of uniform sediment under steadyuniform flow conditions is far from solved,but thepicture is bleak when one looks at the complexitiesintroduced by nonuniformity of sediment and unsteadi-ness of flow.Natural streams are invariably charact-erised by the presence of nonuniform sediment.Further,morphological calculations generally needconsideration of time-dependent discharges as duringa flood.It is heartening that the effects of unsteadinessand sediment nonuniformity have received attentionin some of the papers scheduled for this session.

DOI:

Year: 1985