Hydrodynamic Modeling for Identifying Flood Vulnerability Zones in Mahi Lower Sub-basin

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. Mahi River located in Gujarat State of India, being the third major west-flowing river was inundated in August 2006. This present study aims to develop mathematical model using HEC-RAS 6.0 version to analyze one-dimensional and two-dimensional unsteady flow of water in Mahi lower sub-basin. The river stretch for hydrodynamic modeling starts from Khanpur gauge station located 139 km downstream of Kadana Dam at Mahisagar District of Gujarat to the Mujpur Village near the mouth of Mahi River in Gulf of Khambhat. The simulated results in 1D modeling show that approximately 64.38% of the total cross section have their bank station in overtopped condition for discharge equal or more than 31,061.91 cumec. It has been observed that right bank of river indicating eastern side of Mahi River near Vadodara City is more prone to water spill for higher water levels in River. 2D modeling results identified vulnerable areas of Kherda, Rajupura, and Bhanpura located between Anand and Vadodara cities for flood event 2006 with the highest water surface elevation of 30.95 m. Model outputs can be used as on-structural method of flood vulnerability assessment by government agencies to reduce flood damage.