Criteria for Evaluating Flow Classes in Alluvial Channels

Streambed and water‐surface configurations depend on flow characteristics, fluid characteristics, and sediment characteristics. These streambed and water‐surface configurations are called classes (regimes) of flow. The classes of flow have significant influence on velocity distribution, resistance to flow, rate of sediment transport, and stage discharge relationship. At present several categories of flow classes have been introduced. The most general categorization of flow classes is that of Vanoni, who in 1975 identified eight flow classes. In all the studies done so far it has been observed that there is a significant overlap between the adjoining flow classes. The demarcations between the various flow classes have been drawn by judgment; thus the separation of the various flow classes is subjective. In the present study, flow classes have been demarcated by using dimensionless parameters similar to those used with the Shields criterion of incipient motion. In so doing, a demarcation parameter was developed to demarcate various flow classes for sand‐bed alluvial channels.