Variations in nearshore processes along Nagapattinam coast, India

Abstract

Directional wave data collected at 10 m water depth, at 2 km distance off Nagore from March 1998 to February 1999, were used to estimate the longshore currents and longshore sediment transport rate considering the sea and swell waves separately using the CERC formula. Daily littoral environmental parameters were observed at three stations and longshore sediment transport rate was estimated using Walton’s equation. A comparative study was carried out on theoretical and measured longshore currents. The ratio of spectral energy at the first and second spectral peaks shows that energy at the second peak was more than 50% of the energy at the first peak in 43% of the data collected, due to the presence of sea and swell waves. The difference between the sediment transport rate estimated based on the two methods is around 3.5%. The sediment transport using CERC formula shows that average annual gross transport was 0.448 × 10⁶ m3 and the average annual net transport (towards south) was 0.098 × 10⁶ m3 and this contributes to the supply of sediment to the Palk Bay.