One-Dimensional Hydrodynamic Modelling of Flooding and Stage Hydrographs in the Lower Tapi River in India

The present study addresses the simulation of floods for the years 2003 and 2006 and the development of stage-discharge relationship along the lower Tapi River in India. The river network and cross-sections, for the present study, were extracted from the fieldsurveyed contours of the Tapi River. Using the aforesaid geometry and hydrological data, supplied by the stakeholders, the MIKE 11 hydrodynamic model was calibrated for the 1998 flood using releases from the Ukai Dam (flood hydrograph) and the tidal water level in the Arabian Sea as the upstream and downstream boundary conditions respectively. The calibrated model was validated using low- and high-flood data of the years 2003 and 2006 respectively. The time series of the simulated flood levels were compared with the corresponding observed values at four intermediate gauging stations: Kakrapar Weir, Mandavi Bridge, Ghala village and the Surat city (Nehru Bridge). The model performance was also evaluated using the standard performance index (i.e. ischolar_main mean square error) and was found to be reasonably satisfactory for such a data-scarce region. The rating curves (i.e. stage-discharge relationship) were also developed from the aforesaid calibrated model which would be useful in flood forecasting and development of flood protection measures along the lower Tapi River.