Variability of the local wave regime and the wave-induced sediment transport along the Ganpatipule coast, eastern Arabian Sea

Abstract

For planning coastal protection measures, information on nearshore waves and the wave-induced sediment transport rates are required. This study examines wave-induced longshore sediment transport (LST) rate considering three widely used bulk transport formulae using measured wave data at 14-m water depth covering six years (2011–2016). The study shows that selection of appropriate formulae for estimation of LST rate is important since the estimates based on different formulae vary from 4–5times larger as compared with Kamphuis equation, which is a reliable formula for estimating LST rates across the eastern Arabian Sea. Meridionally oriented coast presents a predominant north to south LST regime as a result of the wave climate, where the lowest values of significant wave heights (Hs) occur during October–April (< 1.5 m) and highest energy conditions occur in the Indian summer monsoon (June–September) when Hs exceed 2 m. Sedimentary dynamics during the monsoon contributes to 77%–88% of the annual LST due to the high wave energy present during this period. Even though the inter-annual variation in annual mean Hs is 6%, the variations in gross LST is up to 22%. The study shows that a small error (∼1-5°) in the estimation of the wave breaker angle leads to a significant error (10%–90%) in the LST rate. Also, 5%–20% error in the wave height leads to 7%–43% error in the annual LST rate.