Effect of long-term wave climate variability on longshore sediment transport along regional coastlines

Long-term changes in wave climate have potential impacts on the evolution of regional coastlines. This study investigates the impact of variable wave climate on the temporal dynamics of longshore sediment transport (LST), which plays a major role in defining the overall coastal geomorphology of regional coastlines. The central west coast of India is considered as the study region. ERA-Interim wave hindcast dataset over the period of 1979-2015 is used to derive the contemporary wave climate in this region. The annual average significant wave height, period, and direction are computed and used to estimate LST of the study region. This region experiences oblique waves from the W-SW direction with an annual average significant wave height and wave period of 1.32 m and 8.10 s, respectively, that induces a gross northerly transport of approximately 450,000 m(3)/year. It is found that the total LST is driven by swell waves and wind waves and shows a decreasing trend of about 5% over the analysis period. The decay in LST is found to be linked with decreases in wave activity in this region. The swell wave induced sediment transport is an order of magnitude higher than the wind wave induced LST. It is observed that the swell generation in the lower latitudes has decreased, resulting in reduced swell wave induced LST in the study area. Both swell and wind wave induced LST show seasonal variation. Finally, a link is established between the seasonal variation of swell induced LST and the cyclogenesis periods. In addition, the wind wave induced 1ST is observed to have a direct link with the latitudinal position of the inter-tropical convergence zone (ITCZ). (C) 2017 Elsevier Ltd. All rights reserved.