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Assessing Compound Floods in a Large Tropical River Basin under Changing Climate
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  • Amina Khatun,
  • Poulomi Ganguli,
  • Chandranath Chatterjee,
  • Bhabagrahi Sahoo
Amina Khatun
Indian Institute of Technology Kharagpur

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Poulomi Ganguli
Indian Institute of Technology Kharagpur
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Chandranath Chatterjee
Indian Institute of Technology Kharagpur
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Bhabagrahi Sahoo
Indian Institute of Technology Kharagpur
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Abstract

Compound flooding, characterized by the co-occurrence of multiple drivers is a cause of concern in many world river basins. High river flows accompanied by high rain events are responsible for severe flooding events. Many studies in the recent past have analysed rain and river-flow dominated compound floods. In this study, we assessed the rain and river-flow induced compound flooding scenarios in a large tropical river basin, the Mahanadi River basin, located in eastern India. Since, many high floods have occurred in the past decade in the Mahanadi River basin, we analysed how the historical flood (in the year 2000) will unfold in a projected climate change scenario (in the year 2080) under RCP8.5. We used the bias-corrected hydro-meteorological data of nine Global Climate Models (GCMs) as input forcings to a hydrologic model MIKE11 NAM-HD to simulate the river flows at the head of the Mahanadi delta. The mean areal rainfall for the delta region and the river-flow simulations are forced into a calibrated and validated MIKE FLOOD model to simulate the historical and projected flood inundations. Comparison of the compound floods with the rain-induced and streamflow-induced floods indicate increased compound flooding in the projected scenario. Both historical and projected floods are found to be predominantly influenced by the river flows. Also, both the areal extent and flooding depth are found to be increasing the projected period as compared to the historical counterpart.