Role of Resistance Coefficient in Seasonal Adjustments in Alluvial Rivers

Using the river, canal, and flume data, it is found that the role played by the seasonal variation in the Manning rugosity coefficient, n, equalizes the sediment transporting capacity with sediment supply in the dune bed-form regime. Aggradation/degradation in a sand-bed river is thus avoided on a seasonal basis. A relation between the dimensionless rugosity coefficient and the dimensionless ratio of stream power to sediment concentration exists in sand-bed rivers for any specific gauge height. Once field measurements of the sediment transport rate are made and such a relationship is worked out, thereafter, it may be possible to estimate the sediment concentration for each observed flow discharge merely by applying this relationship adopting the data of velocity, depth, slope, and bed material size which are routinely observed at a stream-gauging site.