Computation Methods of Discharge in Compound Channels

Abstract

Water which is one of the basic requirements for continuation life occasionally causes floods that threaten the living life. The floods which
are after cloudburst in the summer months or with snow melt at the end of winter frequently occur with flood out of the main bed water.
Sections which are the main channel and floodplains are called compound channels. Floodplains, which are at one or both sides of the main
channel, only occur during flood time. The most important parameter in the design of flood protection structures is discharge. However,
discharge of compound channels varies depending on many factors. Experimental methods, which are mostly developed considering the water
levels in main and flood channels, are often used in flow calculations. In the study, the errors of calculated discharge with Single Channel
Method (SCM), Divided Channel Method (DCM) and Exchange Discharge Method (EDM) were compared in symmetrical and two floodplains
compound channels. Side slopes of main channels are designed trapezoidal and rectangular. Side slopes of floodplains have been constituted
vertically. Comparing the performance of the methods for four different discharge between 9-27 L/s, SCM and DCM have been shown to reach
over 10% relative error value in low discharge. At high discharges, the absolute relative error of DCM drops below 2%. Although the errors
of the methods generally decrease with increasing discharge, the average absolute relative error of all methods is found to be over 5% in the
compound channel which is trapezoidal of main channel side slope.