FLOOD FLOW ANALYSIS DURING RISING AND FALLING STAGES IN A DOUBLY MEANDERING COMPOUND CHANNEL

Natural rivers are predominantly meandering. They are usually composed of a deep main channel and adjacent shallow floodplains. When the main meander channel is flanked by floodplains with meandering levee, it results in a doubly meandering compound channel. This paper explores the flood flow characteristics in a doubly meandering compound channel. It is found that the discharge and relative depth relationship is highly non-linear. The maximum difference in discharge between rising and falling stage is found to be at a relative depth of 0.17. The velocity-water depth relationship is also highly non-linear and characterized by familiar clock-wise loop formation. The extent of loop is more pronounced at a relative depth of 0.17. The depth-averaged 2-D velocity distribution shows that at the bend apex section, the velocity takes maximum along the inner bank while the velocity takes minimum along the outer bank for both rising and falling stages. The velocity in the cross-over section takes the maximum along the centerline of the main channel for both rising and falling stages.