Modeling of lateral velocity distribution in straight compound channels

During flooding, flow enters floodplains and extremely affects the hydraulics of river flow. In this case, estimation of flood discharge with traditional or commonly used methods leads to high errors (up to 40 percent). The most significant method for modifying traditional methods is Shiono and Knight quasi 2-D model which has numerous applications in laboratory and field compound cross sections. In this paper, based on this 2-D model, suitable dimensionless equations for secondary flow effects have been presented for solving the velocity lateral distribution in straight flume and river compound channels. Results of main channel flow velocity of this method have been compared with Shiono and Knight and Ervine et al., models, for some flume and river compound channels. This comparison showed that the proposed equations and Ervine et al. model had the highest and lowest accuracy, with determination coefficients of 0.99 and 0.71 percent, respectively. Also Ervine et al. method may lead to high error in case of asymmetrical compound cross sections and hence, it is not recommended.