Identification of eddy viscosity parameter and depth-averaged secondary flow in a compound channel with and without emerged vegetation on floodplains

The Shiono–Knight method (SKM) was used to calculate a lateral profile of the depth-averaged velocity and determine the flow rate for a compound channel, both in the presence and absence of emergent vegetation on the floodplains. The SKM is an analytical solution of the Navier–Stokes equations. The effect of vegetation (trees) on flow was simulated using two approaches: with an averaged friction factor and by adding a drag force term in the Navier–Stokes equation. Based on flume and field experiments in compound channels with and without emergent vegetation, values of parameters for the dimensionless eddy viscosity and the secondary flow term were identified using the Monte Carlo sampling technique. The surface of the main channel bed was smooth and made of concrete, whereas the floodplains and all sloping banks were covered by cement mortar composed of terrazzo. Calculations were performed using various models, applied to both laboratory and field data sets. The obtained velocity and flow rate distributions were consistent with observations.