![]() ![]() It has long been recognized that tide-surge interaction is a non-linear phenomenon. Therefore, quantitative insights into tide-surge interaction are very important for the prediction of storm tide level and flood risk assessment. Compared with observations, errors in a simple linear superposition of the astronomical tide with a separately computed surge are found to be up to 1–2 m ( Rego and Li, 2010). However, tide-surge interaction has long been recognized as one of the most important contributors in the storm surges and peak water levels in coastal regions ( Proudman, 1955, 1957 Doodson, 1956 Bernier and Thompson, 2007 Zhang et al., 2010). To be able to predict the peak water levels, operational systems, and research studies often superpose an atmospheric-only forced storm surge onto the astronomical tide without considering the effect of tide-surge interaction ( Peng et al., 2004 Bobanović et al., 2006 Graber et al., 2006). When combined with the astronomical tide, storm surges often result in extreme water levels and can bring devastating damage to coastal areas, especially for those low-lying areas bordered by extensive continental shelves and exposed to the regular passage of typhoons and storms ( Bertin et al., 2012 Zhang et al., 2017). Storm surges are abnormal variations of sea level driven by atmospheric forcing associated with extra-tropical storms or tropical cyclones (also known as hurricanes and typhoons). Detailed analysis using the “addition” approach indicates that the quadratic bottom friction, shallow water effect, and nonlinear advective effect play the first, second, and third most important roles in the tidal-surge interaction in the estuary, respectively. The widely used “subtraction” approach is found to be unsuitable for the assessment due to the “rebalance” effect, and thus the new “addition” approach is proposed along with a new indicator to represent the tide-surge interaction, from which more reasonable results are obtained. In order to numerically assess the contributions of three non-linear processes in the tide-surge interaction and quantify their relative significance, the widely used “subtraction” approach and a new “addition” approach are tested in this study. ![]() The results show the strong tidal modulation of the surge level, as well as alteration of the phase of surge, which also changes the peak storm tidal level, in addition to the tidal modulation effects. Three different types of model runs are conducted in order to separate the water level variations due to the astronomical tide, storm surge, and tide-surge interactions in the Pearl River Estuary. The wind field of Typhoon Hato is firstly reconstructed by merging the Holland parametric tropical cyclone model results with the CFSR reanalysis data, which enables the model to reproduce the pure astronomical tides and storm tides well in particular, the distinctive oscillation pattern in the measured water levels due to the passage of the typhoon has been captured. In this study, the characteristics and mechanisms of tide-surge interaction in the Pearl River Estuary (PRE) during Typhoon Hato in August 2017 are studied in detail using a 3D nearshore hydrodynamic model. 7Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai, China.6Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, School of Marine Science, Sun Yat-sen University, Guangzhou, China.5College of Harbor, Coastal and Offshore Engineering, Hohai University, Nanjing, China.4National Oceanography Centre, Liverpool, United Kingdom. ![]()
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