Storm surge responses to the representative tracks and storm timing in the Yangtze Estuary, China

Abstract The study explores storm floods in the Yangtze Estuary to examine the surge responses to the variation of storm tracks and storm timing under the combined effect of astronomical tides, storm surge, and runoff. A new method of typhoon scenario construction is developed based on a hypothesis of the influenced sphere of the Yangtze Estuary (ISYE) raised in the paper and two representative typhoon tracks, the direct landing typhoon (DLT) and the offshore northward typhoon (ONT), are studied by the worst cases with five scenarios of tidal range using FVCOM. The result shows that the surge threats of DLT and ONT concentrate on the upper estuary and inner estuary, respectively. The phase shift due to the acceleration of phase speed, resulting from the surge-tide interaction and the flood current, is proposed to be the primary factor increasing surge in the rising-tide. A transfer of the peak surge position is detected outside the estuary, which can well explain the abnormally small surge near the low-tide. Further, the larger tidal range tends to attenuate surge levels due to the enhanced depth in the inner and upper estuarine areas.