A 1D–2D Coupled Hydrodynamic Model for River Flood Prediction in a Coastal Urban Floodplain

Abstract

In this work, a one dimensional–two dimensional (1D–2D) coupled hydrodynamic model is developed for prediction of water levels in the lower Tapi River and its coastal urban floodplain (Surat city in Gujarat, India). A one-dimensional (1D) hydrodynamic model, calibrated for the 1998 flood, is coupled with a two-dimensional (2D) hydrodynamic model of an urban floodplain with due consideration of the upstream (releases from Ukai reservoir) and downstream (tidal level of the sea) boundary conditions. The resistance coefficient for the floodplain is estimated using satellite imagery based on the land use and land cover pattern. The coupled hydrodynamic model is validated with independent data for flooding in the year 2006 and is used to develop a stage-discharge curve along the lower Tapi River for computation of the stream power during the flood. The methodology for river flood prediction on a coastal urban floodplain using the 1D–2D coupled hydrodynamic model is generic and can be applied to similar geographical conditions.