UNCERTAINTY ANALYSIS OF QUASI-TWO-DIMENSIONAL FLOW SIMULATION IN COMPOUND CHANNELS WITH OVERBANK FLOWS

Flow in compound channels with overbank flows becomes more complex because of shear interactions between flows in main channel and flood plains, lateral momentum transfer and secondary flows. Compound channels have interesting applications in flood control, civil engineering and environmental management. Because it is difficult to obtain sufficiently accurate and comprehensive understandings of flow in natural compound rivers, the developed models of flow in overbank flows have many uncertainties. The main aims of this paper are to analysis and quantify the uncertainty results of quasi two dimensional flow modeling in compound channels. In this paper a quasi two dimensional depth averaged model, known as Shiono and Knight Model (SKM), in compound channel is used and uncertainty analysis of its simulation results is done based on Monte-Carlo simulations. Results indicated that although the SKM model can simulate quasi-two-dimensional flow accurately but it has many uncertainties in simulation results. The uncertainties of model results in high are greater than low flows. Also uncertainties in discharge capacity and shear stress are greater than those for velocity profiles. Overall results cleared that the SKM model, beyond from its strong physical basics, requires rigorous effort on local calibration processes, especially for high flood flows and these limit its global applicability and generalities.