Modeling of Flood Inundation Extent in Data-Scare Regions: The Case Study of Bhavnagar District

Flood models can be a valuable source of information for flood risk assessments because they predict inundation extents. Due to the impact of climate change, the semi-arid zone of Gujarat is experiencing an increase in annual rainfall. Bhavnagar and the surrounding district received around 521 mm of rain in August 2020, compared to Bhavnagar district’s average annual rainfall of 658 mm. The Kalubhar and Ranghola dams in the Bhavnagar district were filled with water, causing high flows in the Kalubhar, Rangholi, Keri, and Ghelo rivers. The flows from these four rivers merge before meeting the Gulf of Khambhat. Despite the lack of data, an attempt has been made in this study to develop a two-dimensional flood model for this region using HEC-RAS v6.0. The study shows that the flood in the region was caused by a high amount of rainfall combined with unplanned development along the coastal line. Based on the simulated results and the difficulties encountered during model development, recommendations and guidelines for resolving the waterlogging problem and reducing the extent of flood inundation for the Bhavnagar coastal region were provided. The study will aid government officials and stakeholders in determining flood prevention measures.