Analyzing wave direction scenarios for large waves in deep water and its impact on littoral drift

Abstract

In this study, four types of wave direction scenarios in large waves greater than 3 m in deep water are examined by analyzing NOAA's wave hindcast data spanning over 40 years. The results reveal that wave direction changes at the starting, peak and ending of large/storm waves, accompanying by changing wave heights with wave direction becoming in perpendicular to the coastal orientation when waves reaching a peak. Within the bulk of NOAA wave data which last 1.65 days, 55.1% of the large/storm waves had wave direction returning to the starting direction on the wane of the waves, while the remaining 44.9% reversed to the opposite side of the starting direction. Based on this finding, littoral drift is calculated for each scenario by the CERC equation, on the basis of deep water wave parameters. The resulting littoral drift is then used in a numerical model to calculate shoreline changes at Jeongdongjin Beach in Korea, where a natural groin block the longshore sediment transport. The result of shoreline change in the vicinity of the groin suggests beach may become stable about one day after the end of a short-term large wave/storm event, or 2 days after the peak wave height.