RESISTANCE OF COARSE SEDIMENT BEDS

Abstract

Flow resistance mainly deals with the prediction of velocities of flow in terms of easily measured channel properties. The main objective of a study of flow resistance is to predict the velocity of flow in open channels for the purpose of design of canals, development of depth discharge relationships, river training works etc. Considerable amount of work has been done for understanding the behaviour of canals and rivers wherein the bed material is rather fine such as sand. On the other hand if one looks into the upper reaches of rivers which fall in mountain region, the behaviour of such a river is totally different from that of arlauvial rivers. This is so because bed material is relatively larger in size and range. Therefore, there is a need to develop suitable relationship for the prediction of resistance to flow in such gravel rivers. The work done so far by various investigators on the resistance of coarse sediment beds is summarized in this study and their results have been checked with the help of flume and field data from various sources. It has been observed that these methods have certain limitations; mainly because of the fact that these studies are largely based upon either flume study or field study only. Hence there is a need for a relationship which will not only be applicable to field observations but also to the flume studies.