A flood assessment of data scarce region using an open-source 2D hydrodynamic modeling and Google Earth Image: a case of Sabarmati flood, India

Flood assessment is an important decision-making activity which helps the decision maker to reduce the flood catastrophe in flood prone area. However, flood assessment requires massive datasets, i.e., river morphology, river cross-sections, flood hydrograph, high-resolution digital elevation model (DEM), land use/land cover (LULC), drainage map, soil map, slope map, rainfall, observed high flood level, severe flood hazard map, zone or ward maps, etc., for developing and validating a model for flood emergency planning. In addition, collection of these datasets and availability of datasets for modeling work are a great challenge in developing country. To overcome this limitation and developing the hydrodynamic model under the optimum number of datasets, a case study is executed over Sabarmati River, Ahmedabad city. HEC-RAS 5 is an open-source hydrodynamic model which is applied to develop a flood inundation, water surface elevation, and velocity of flood for flood 2006. The model is simulated under the unsteady flow conditions. The simulated results are overlay on Google Earth Image and flood inundation areas are clearly identified. The river roughness between the Chiloda Bridge, Gandhinagar and Vasana Barrage, Ahmedabad, India is identified and validated using NS and RMSE statistics method. Overall, the executed approach presents the case of development of hydrodynamic model and preparation of decision-making system under the scarce datasets for flood assessment.