Flow Resistance in a Compound Channel with Diverging and Converging Floodplains

Experiments were performed in the symmetric compound channel with diverging and converging floodplains for different relative flow depths to investigate the resistance characteristics of overbank flow in nonprismatic sections. The effectiveness of Manning's n, Darcy-Weisbach's f and Chezy's C are analyzed. Manning's roughness coefficient relies upon the nondimensional parameters like width ratio, aspect ratio, relative flow depth, angles (diverging and converging angles), relative distance, bed slope, Reynolds number, and Froude number. A multivariable regression model has been developed by taking care of the aforementioned geometric and hydraulic parameters to estimate the Manning's roughness coefticient for nonprismatic compound channels. The nonlinear regression models are developed using pertinent experimental data obtained from laboratory experiments and the data from other researchers on the compound channel with non-prismatic floodplains. The present model gives satisfactory results as compared to other approaches for different experimental channels and field data by providing less error. (C) 2018 American Society of Civil Engineers.