Nearshore Sediment Transport in a Changing Climate

Abstract

The impact of changing wave climate on the most important nearshore process, longshore sediment transport (LST), along the central west coast of India is investigated. The main purpose of this study is to provide a better understanding of the meteo-marine climate of the central west coast of India, which is highly influenced by the Arabian Sea and the Indian Ocean. To understand the contemporary evolution of the coastline, hindcast wave climate from ERA-Interim wave data (1979–2016) is used. The annual average significant wave height (Hs), wave period (Tp) and wave direction (α0) are obtained and used to estimate annual LST. This region receives oblique waves from the W-SW direction which induces a huge gross northerly transport. It experiences two types of waves, swell waves (remotely generated waves that travel thousands of kilometres before hitting the coastline) and wind waves (also known as seas, which are locally generated), both of which are responsible for coastal sediment transport. The swell waves are the major component of a total wave system. It has more strength than the locally generated wind waves and dictates the wave direction and significant wave height at any given point of time. Therefore, the swell wave-induced LST is an order of magnitude higher than the wind wave-induced LST. It was observed that the sediment transport has a seasonal nature due to the influence of monsoonal winds in this region. The total LST in the central west coast of India shows a decreasing trend due to the reduced swell generation in the lower latitudes of the Arabian Sea and the Indian Ocean.