Wave transformation and attenuation along the west coast of India: Measurements and numerical simulations

Abstract

Waves measured at a few locations along the west coast of India were analyzed to study modification and attenuation of wave energy in the nearshore regions. It has been found that the reduction in wave height is relatively lower (less than 10 percent) between two nearshore depths off Goa (25 m and 15 m) and Ratnagiri (35 m and 15 m), central west coast of India and is higher (22 percent) off Dwarka (30 m and 15 m), northwest coast of India. It is observed that the diurnal variation in waves decreases from north to south along the coast, as the intensity of sea breeze decreases from north to south. Swell attenuation due to opposing winds (from NE) is observed along the Ratnagiri coast during NE monsoon. The growth of wind seas (from NE) towards offshore and their modification by opposing swells (from SW/SSW) significantly contributed to the reduction in wave heights at shallow water depths off Dwarka. The role of opposing winds in the attenuation of swells along the west coast of India during NE monsoon season is significant. Numerical simulations were carried out to study the wave transformation between the depths 100, 50, 20, 10 and 5 m off Mumbai, Goa and Kochi. Diurnal variation is evident during the pre-monsoon season, and the magnitude of variation decreases from north to south.