The drag force of vegetation was introduced in the depth-averaged momentum equation and the analytical solutions of depth-averaged velocity and bed shear stress were presented. Based on the feature of cross-section of vegetated rectangular compound channels,the force balance equation was built at the interface between main channel and floodplain and then two boundary conditions were carried out.The predicted results of these two boundary conditions were compared and their results were almost the same at a high relative flow height while some differences were in the shear layer at a low one.The continuity condition which contained the wall shear stress in the main channel provided better predictions.Finally,eight groups of experimental data were applied to verify the predicted ability of the better boundary condition.The results showed that optimal secondary flow coefficients in each domain result in much better lateral distributions of depth-averaged velocity and bed shear stress,especially in main channels.Good predicted results can be obtained by choosing appropriate secondary flow coefficients in each case.
