Hydrological and hydrodynamic modelling for flood management: A case study of the Yamuna River Basin in Delhi

Yamuna River (Delhi), India. The anthropogenic activities within the vicinity of the floodplain reduce the river's margin and subsequently alter the magnitude of the river's flow. The encroachment of riverbeds leads to waterlogging and flooding in urban areas, thereby causing damage to property, human life, etc. It necessitates a comprehensive study of the floodplain and changes in its proximity such as encroachment of floodplains to carry out any further activities with certainty. This study employs a two-dimensional model to simulate the Yamuna River's (YR) hydrodynamic characteristics, focusing on India's Delhi region. Simulated flood flows are employed to evaluate floods of once in 10, 20, 25, and 30-year return periods using the flood frequency analysis for 1951–2013. The model validation results indicated that the model could mimic the flood depth in YR. Simulation results revealed that the floodplain's encroachment had increased the severity of the floods. The increase in the extremeness of flooding events, i.e., from once in a 10-year return period to a 30-year return period event, is expected to increase the areas at risk of floods by 12 %. The model also offers a potential platform for evaluating other alternatives, such as further encroachment, for a business-as-usual scenario or for restoring the Yamuna floodplains. With such a comprehensive perspective, floodplains' role enhances river basin resilience to climate and anthropogenic changes and increases flood safety. Comparison of Water Levels for Scenario 1 (With Embankment), Scenario 2 (Without Embankment), and Scenario 3 (Future Encroachment) • Established efficacy of newly developed iRIC model in mimicking hydrodynamics of Yamuna River. • Quantified the potential increase in flood depth due to further urbanization within the floodplain. • Specific areas at high risk of flooding in the Yamuna River Basin were identified. • Scenario analysis for various return periods (10, 20, 25, and 30 years) to assess flood dynamics under different conditions. • Highlighted the crucial role of natural floodplains in attenuating floods and mitigating flood risks.