Abstract: Floods can cause widespread devastation, resulting in loss of life and damages to personal property and critical public health infrastructure. River flooding is the most common type of flooding in many parts of the world. It occurs when a water body exceeds its capacity to hold water and usually happens due to prolonged heavy rainfall. Narmada river located in Gujarat state, India, being major west flowing river was inundated in august 2006. This present study aims to develop mathematical model using HEC-RAS 6.0.0 version to analyze one dimension and two-dimension unsteady flow of water in Narmada lower sub-basin. The river stretch for hydrodynamic modelling starts from Garudeshwar gauge station located 14 km downstream of sardar sarovar dam at Narmada district of Gujarat to the mouth of Narmada river in gulf of Khambhat. The simulated results in 1D modelling show that that approximately 64.38% of the total cross section, have their bank station in overtopped condition both for discharge equal or more than 31061.91 m3 /s. It has been observed that right bank of river indicating eastern side of Narmada river near Vadodara city is more prone to water spill from higher water levels in River. 2D modelling results show that highest water surface elevation was observed in low lying areas are of Kherda, Rajupura and Bhanpura located between Anand and Vadodara city are mostly inundated. Model outputs can be used as Non-structural method of flood vulnerability assessment by government agencies to reduce flood damage.

Keywords: Inundate, Flood vulnerabilty, Water surface elevation, 1D & 2D model.

| DOI: 10.17148/IARJSET.2022.9812