A 2D hydrodynamic model for river flood prediction in a coastal floodplain

A two-dimensional (2D) hydrodynamic model is developed for the prediction of the water level in the lower Narmada River and its coastal floodplain passing through the Bharuch city of Gujarat, India. The 2D hydrodynamic model is calibrated for the flood of 2006 with due consideration of upstream (releases from Sardar Sarovar Dam) and downstream (tidal level of the sea) boundary conditions. The resistance coefficient of the floodplain is estimated using Landsat imagery based on the land use land cover pattern. The developed model is validated with independent data from a flood in 2013. The developed model is utilized to predict flood levels for the discharges corresponding to a 100-year return period flood, observed maximum flood and standard project flood of Sardar Sarovar Dam, which is situated upstream of the study area on the Narmada River. The model is further used to study the variation in water levels in the lower Narmada River due to the construction of the proposed Bhadbhut barrage for different gate-opening and embankment scenarios. This will be helpful in determining the height and length of the embankments along the river for flood protection. This is the first study in the lower Narmada River after the completion of the Sardar Sarovar Dam and after reaching its full capacity on September 17, 2019. The methodology proposed in this study for river flood prediction on the coastal floodplain using a 2D hydrodynamic model can be applied to similar geographical conditions.