Laboratory study of bed material withdrawal in farm turnouts

Depth of flow in the flume, discharge in the flume, turnout elevation from the concrete bed of the flume, and the discharge through the turnout were the variables whose effect on the variation of sediment discharge through the turnout was to be determined. The statistical analysis of the data (Eq. 5-1) indicates that the sediment discharge through the turnout is almost directly proportional to the sediment concentration in the flume. Data taken at two different turnout elevations confirmed (Fig. 5-3) that most of the sediment load was transported close to the bed of the channel and the variation in sediment concentration at higher elevations from the bed of the channel was not significant. Based on a series of special runs plus visual observation, it was found that the amount of sediment discharge through the turnout was significantly affected by the bed form movement in the flume. A collapse of sharp peak or unstable formation which was irregular in time and space in the vicinity of the turnout would increase the sediment discharge through the turnout considerably. The analysis of data shows that the scour pit formation near the turnout remains geometrically similar under different conditions of flow in the flume and the turnout. It was also found that the depth of scour pit increase with an increase in the discharge ratio.