A Study on Some Characteristics of an Alluvial Channel for Varying Flows

An attempt has been made here to study on some characteristics of an alluvial channel when its pattern undergoes a continuous change under two different flows in the context of fluvial and analytical data. The effect of inclusion of a training structure on these channels has also been studied. An experimental alluvial channel of 91.44 m in length with a trapezoidal cross section of 10 cm in depth, 10 cm bed width and side slope 2:1 was laid on a sand tray of 91.44 m in length and 9.144 m in width. At the entrance of the channel, an initial curvature was introduced to accelerate the meandering process. At first, a steady discharge of 0.003 cumecs was circulated through the experimental straight channel for 150 h when a regime channel was obtained. It was noticed that only three successive meanders of about same length had developed up to 36.576 m along the longitudinal direction of the channel. The rest portion of the channel remained straight. At this stage, a river training structure (barrage) was introduced at a section of 17.069 m from entrance of the channel. With same discharge, the flume was again allowed to run for 150 h until a regime channel was attained. The experiment was repeated with another discharge of 0.007 cumecs. From data analysis, it may be concluded that in the meandering reach, any change in cross-sectional flow area is associated with the increase of water surface width or total bed width which is again accompanied by increase in boundary resistance or power expenditure. As such, there may be a good correlation between scour and increase of water surface or total bed width and hence to power expenditure in the meandering reach. But it may not exist in the straight reach of the same channel.