486 / 2024-09-18 00:45:52

Interactions of tides and surge during a typhoon in macro-tidal Hangzhou Bay

Macro-tidal estuaries,tide-surge interaction,tidal amplitude,wind intensity,Hangzhou Bay,typhoon

Session 24 - Estuaries and coastal environments stress - Observations and modelling

In macro-tidal turbid estuaries and coastal waters, typhoons combine with macro-tides and high turbidity, posing significant geological, ecological, and socio-economic risks. Hence, understanding the interactions between macro-tides and storm surges is both scientifically and practically important. This study examines these interactions in Hangzhou Bay, a macro-tidal and turbid estuary, during Super Typhoon Chan-hom. We developed and calibrated a tide-surge model for Hangzhou Bay, incorporating reconstructed coastal wind field datasets and wave-current interactions. Numerical tests were conducted to investigate the characteristics and mechanisms of storm surges in the bay. Our findings reveal that during the typhoon, nonlinear surges show periodic fluctuations and spatial variability. The peak nonlinear surge at the bay’s head is higher than at its mouth. Astronomical tides enhance the surge during low slack water and suppress it during high slack water. At the bay’s mouth, tide-surge interactions are primarily influenced by local acceleration and friction terms, with the advection term playing a secondary role. Conversely, at the bay’s head, friction and flow terms dominate the nonlinear interactions. The amplitude and phase of astronomical tides significantly affect storm surge characteristics. However, semi-diurnal tides have the greatest impact on surge in the bay, followed by diurnal components, with long-period and shallow-water tides having the least influence. Semi-diurnal and diurnal component tides amplify or inhibit nonlinear surges during low and high slack waters, respectively, while long-period and shallow-water tides generally inhibit nonlinear surges.