An advanced hydraulic model was developed by improving the numerical implementation of internal boundary condition and the prediction of scour depth to analyse hydraulic effects in operation of multi-function weir during the flooding season. The proposed model calculates overflow at fixed weir and gate discharge controlled by movable weir depending on the computed water stages on the upstream and downstream reach compared to conventional model applying internal boundary condition specified as

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... escribed stage or rating curve. In addition, it can predict time-dependent scour depth considering soil properties under unsteady state in order to investigate the hydraulic effects on bridge structure located downstream. A historical flood event was applied to demonstrate the verification of the model as simulation results were compared with observations on monitoring station. It was shown that the prediction of water stages, gate discharges, and scour depth enable gate operation rule to minimize the effect of flood stage rising by movable weir and scour depth development by fixed weir.