Modeling of Coastal Inundation in Response to a Tropical Cyclone Using a Coupled Hydraulic HEC‐RAS and ADCIRC Model

Abstract

AbstractCoastal flooding as a combined effect of storm‐tides, river discharge (RD) and rainfall during a cyclone period is of a major concern, particularly, in the river delta regions. The low‐lying Mahanadi river delta located in the maritime state of Odisha along the east coast of India is highly prone to inland flooding due to any impinging cyclone in the region. Hence, computation of coastal flooding is seen for the 1999 Super cyclone and the 2013 Phailin cyclone using a standalone Advanced Circulation (ADCIRC) and a coupled Hydrologic Engineering Center River Analysis System and ADCIRC model. The Mahanadi, Brahmani, and Baitarani rivers are included in the computational domain with representative depths based on available river cross‐sectional data. The model simulations infer that inundated coastal area is enhanced by 64% after representing the river delta in the domain, while the RD from the upstream contributes an additional 14%. The effect of RD and the role of land use/land cover on the computation of flooding during the 1999 Super cyclone is also investigated. The coupled system is used to quantify the contribution of precipitation on inland flooding during the cyclone period. The results signify that the inundated area becomes almost double after including rainfall data in both the cyclonic events. Also, the model generated inundated area during the Phailin cyclone is in a better match with the satellite image, demonstrating the coupled system can simulate a reliable inland flooding in the delta region. It concludes further that it is essential to resolve the river systems and incorporate hydrological components, like RD and precipitation for precise computation of inundation.