Near-real time inundation mapping of the kosi river

The Kosi River is a major cause of floods in Bihar. The Kosi River that emerges from Himalayas dissipates its energy on the plains in India leading to flood inundation in a large area during the monsoon (June to September) season. The sediment load carried by the river and fluctuations in its peak discharge accelerates the flood damage. In the present study, using hydrologic (Variable Infiltration Capacity (VIC)) and hydraulic (HEC-RAS) models, a methodology to develop near real time inundation maps for the Kosi River reach in India is presented. Near-real time satellite precipitation products downloaded on daily basis are used for driving the hydrologic model to develop flood hydrograph at the inlet of the river reach in India. The hydraulic routing of flood hydrograph through the reach is performed using 2D unsteady analysis in HEC-RAS. Linear bias correction method is adopted in the study for correcting precipitation as well as the temperature data required for hydrologic modeling. The inundation maps developed in the study are evaluated using remote sensing products and observed river stage data. The results highlight the importance of observed discharge data for evaluating the HEC-RAS model, elevation data, observed cross-sections, and information on existing hydraulic structures for further refinement of the model results. However, the results of the study can be used for short term and long-term non-structural and structural flood management activities.