Investigation of complex coastline geometry impact on the evolution of storm surges along the east coast of India: A sensitivity study using a numerical model

Abstract. Comprehensive investigation is made on the generation of storm surges along the coast in response to complex coastline geometry using a standalone ADCIRC model. The study initially deals with sensitivity experiments by using various idealized concave/ convex model domains with the same intensity of parallel cyclone tracks. It demonstrates that a sharp curvature along with the landfall location of each track within the domain has more influence on the surge evolution. Peak surges (PS) are generated in the domain for the tracks possessing strong onshore winds, while intense alongshore winds are responsible for PS spreading along the coast. The time evolution of both positive and negative surges along the coast is also demonstrated. The propagation of energy per unit length associated with surge waves is computed for concave coasts to explain the funnelling effect. Development of PS is also seen with actual intricate coastal stretch having concave and convex coastlines along the east coast of India using parallel tracks, which is consistent with that of idealized experiments. Further simulations are carried out along real coastlines with different approach angles of the track exhibit that maximum PS are not always aligned to the right of the track. Depending on track angle, PS may also develop on the left side. Experiments on real coastlines also indicate that PS in the concave coastline is more influenced by cyclone’s radius of maximum winds. Surge generation with different radius of maximum winds is seen to the left side of the track though the cyclone is not making a landfall in this region. Simulation with a recent cyclone, Michaung reveals that occurrence of storm tides is also seen to left of the landfall as the track moves parallel to the coast, which agrees with the observations. This study signifies importance of local coastline configuration, particularly in the concave coasts, on the intensification of storm surges.