Flow Discharge and Energy Grade-line in Compound Channels

In order to explore the structure and hydraulic behavior of rivers and compound channels, discharge and energy grade-line are of great importance. By dividing a cross sectional shape of those channels to its sub-sections, e.g. the main channel and floodplains, flow discharge is computed for each section and then flow discharge is determined for the whole section. This method is called as Divided Channel Method (DCM) and there is another method called Simple Channel Method (SCM). On the basis of dividing channel method some other methods are also developed, where the important one is the method of Exchange Discharge Model (EDM). The method of EDM is developed by using the effects of momentum transfer on the interaction surface between the main channel and floodplain. In this research, the flow discharge and energy grade-line are computed for the data collected from the Flood Channel Facility (FCF) of England and elsewhere applying SCM, DCM and EDM methods, in which a C++ computer programing was used. The results show that the EDM method gives the lowest relative error compared with the other methods (for establishing stage-discharge curves). Also, using EDM method and HEC-RAS software, the results for computing energy grade-line (e.g.l.), the method of EDM reveals the lowest relative error for establishing e.g.l. curves. Two simple linear equations are presented for relative depths lower and upper than 0.15. It therefore gives dramatic welfare results about 36% for estimating flow discharge and 34% for estimating energy grade-line.