Numerical modelling of overbank flood routing

This paper presents the numerical modelling of overbank flood routing using the one-dimensional model RIMA and the two-dimensional model CCHE2D. These models are initially calibrated using data obtained in laboratory experiments of the UK Flood Chanel Facility series 02 corresponding to a straight symmetric compound channel with overbank flow. Different spatial and temporal resolutions and turbulence closure models implemented in CCHE2D were applied in order to achieve an appropriate hydraulic representation of the phenomenon. Further comparisons of these results with other approaches for overbank flow, such as the Coherence (COH), the RFMFEM model based on the Shiono & Knight Method (SKM), the ISIS Conveyance Estimation System (CES) and the Exchange Discharge Model (EDM) are also shown. Overbank flood routing of a synthetic hydrograph in a hypothetical river having the same cross section as the laboratory channel is then illustrated applying RIMA and CCHE2D numerical models for several scenarios. Results obtained with different approaches are analysed, their implications on modelling of overbank hydrodynamics are discussed and conclusions are presented.