On the improvements in nearshore wave height predictions using nested SWAN-SWASH modelling in the eastern coastal waters of India

Abstract

Nearshore wave prediction is an area of research which still demands continuous developments and the accuracy of wave models in the nearshore regions, is known to be limited. In this work we focus on an improved coastal prediction across east coast of India and this is one step forward to achieve accurate nearshore predictions using nested wave models. The study used two modelling setups, SWAN and SWAN-SWASH with boundary conditions from deep water model WAVEWATCH III. The comparison of wave hindcasts over the east coast of India with buoy measurements at four nearshore locations, represents a higher accuracy in simulating significant wave height (Hs) with a high correlation and high index of agreement, using nested SWAN-SWASH in comparison to SWAN only. Further the accuracy of the models was also evaluated during an extreme event such as Hudhud Cyclone, which showed a better match using SWASH than SWAN at the Visakhapatnam coastal location. The sensitivity of the SWASH model with different grid resolutions was also tested to arrive at the best grid resolutions for achieving accurate nearshore predictions. Hence, a nested SWAN-SWASH setup should be adopted to locally advance the wave prediction in the nearshore regions, reducing the underestimation of wave estimates with SWAN only setup.