Flood modelling for a data-scare semi-arid region using 1-D hydrodynamic model: a case study of Navsari Region

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. The one-dimensional (1-D) hydrodynamic model is used to evaluate the geomorphic effectiveness of floods on the Ambica river basin, South Gujarat region. The study region was subjected to frequent flooding. Major flood event occurred in the year 1981, 1984, 1994, 1997, 2001, 2003, 2004, 2006, 2013 and 2014. In the present study, the geometry of the Ambica river, floodplain of Unai, and past flood data have been used to develop a 1-D hydrodynamic model using HEC-RAS (6.0.0)software. After collecting the required data, the 1-D hydrodynamic model has been developed to simulate the floods of the years 1984 and 1994. The segment of the Ambica river reach with approximately 9 km length between Padam Dungari to Sidhai village is selected for analysis. The study area consists of 23 cross-sections. The model is used to evaluate steady flow analysis, flood conveyance performance, and uniform flow analysis. The outcome obtained from the model is in the form of water depth and water surface elevation. Based on the above results, it shows that the low-lying areas of Navsari city are susceptible to flooding when the discharge in the river exceeds 6500 m3/s. This study can be utilised for disaster management, flood management, early warning system by authorities in addition to infrastructure growth decisions.