Parameter Estimation of a 2D Mathematical Model for Multi-Stage Compound Channels

Abstract While a significant body of research has been focused on classic compound channels, few studies have focused on the multi-stage compound channels. Multi-stage compound channels have more than one floodplain on each side of the main channel. In these channels, when the flood occurs and the main channel is filled, the first floodplain is activated, and then when this floodplain overflows, the second floodplain immediately participates. In this study, three parameters of the two-dimensional model of Shiono and Knight (SKM) are estimated for multi-stage compound channels. Through calibration process, it was found that the effect of eddy viscosity and secondary currents in these channels is significant and should be considered. The calibrated SKM showed a good agreement between the observed and calculated lateral velocity and also bed shear stress distributions, total flow discharges as well as the zonal flow rates. Mean and maximum errors in estimating the total flow discharges were 4.1 and 9.7 percents, respectively. These errors for main channel’s flow discharges estimation were obtained as 4.9 and 10.6 percents, respectively. Meanwhile, the vertical divided channel method, widely used in water engineering packages, with an average error of 23% and a maximum error of 32% does not provide reliable results for total flow discharges. Results showed that SKM can estimate the total and the subdivision flow discharges in multi-stage compound channels with reasonable accuracy.