Flow Characteristics of a Compound Channel Due to Vegetation

River flow and river geometry are dynamic throughout its length. The river's flow adjusts as it observes a change in its geometry or due to an obstruction. Continuity Equation suggests that the change in the area of a cross-section of flow, which may be due to a change in its geometry or obstruction, necessarily means a change in flow velocity if other parameters are kept constant. Gradual changes may not show adverse effects, but a sudden change in the river geometry causes even higher stresses at the interaction point. It is accompanied by strong lateral flow, which causes lateral erosion. Laboratory experiments were conducted in a 17.2 m long, 1 m wide recirculating flume to observe these additional stresses. The flow passed through the obstructions in the form of emergent vegetation and submerged vegetation at half-width of the 5 m long test section. The change in the velocity profile of the entire cross-section suggests an increase in velocity away from the obstruction. It leads to achieving incipient motion conditions. Also, a slight increase of flow depth is observed at the obstruction, which can cause flooding in areas with already bank-full flow upon combining. The velocity increased on the unvegetated part of the cross-section as the obstruction in the form of flexible emergent vegetation was present on the right side. In contrast, the velocity increased at the center of C/s as submerged vegetation was present in the bottom right half. The movement of the high-velocity line away from the obstruction may be dangerous in the case of narrow rivers.