Increase in overtopping rate caused by local gust-winds during the passage of a typhoon

ABSTRACT

A field survey of Fukuura Coast (in Tokyo Bay, Japan) revealed during the passage of Typhoon Faxai in 2019 waves with considerable momentum caused significant wave overtopping, resulting in structural damage to coastal defenses and localized flooding. The hindcasted wave height using a third-generation wave model was not high enough to explain the extent of the local damage at Fukuura Coast, likely due to such methods failing to take into account the strong gust-winds recorded during the passage of the typhoon. To solve such problems the authors developed a new numerical model that takes into account the dynamic interaction of air and water, based on the finite volume method (FVM) and the volume of fluid method (VOF). Although this model still slightly underestimates the measurements in the experiments previously conducted by different authors, it is better than existing methods when estimating the overtopping rates under strong winds. The model was then applied to a real-scale model of Fukuura Coast, where by taking into account strong gust-wind speed of 41 m/s the authors were able to explain the phenomena that took place.

KEYWORDS:

• Wind waves
• wave overtopping
• gust-wind
• openfoam
• local scale disaster

Acknowledgments

The observed meteorological data was retrieved from AMeDAS (https://tenki.jp/amedas/map/). Typhoon best track data is available at Japan Meteorological Agency (https://www.jma.go.jp/jma/jma-eng/jma-center/rsmc-hp-pub-eg/trackarchives.html). The observed wave data is available at NOWPHAS (https://www.milt.go.jp/kowan/nowphas/index_eng.html). The present work was financially supported by Japan Science and Technology Agency (JST) as a part of the Belmont Forum, Re-Energize DR3 project, Grant Number JPMJBF2005, and by Japan Society of Promotion of Science (JSPS) KAKENHI Grant Number JP21J20393, JP20KK0107 and JP19K24677. The work was also performed as a part of the activities of the Research Institute of Sustainable Future Society, Waseda Research Institute for Science and Engineering, Waseda University.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

¹ The ground elevation in Japan is measured with reference to T.P. (Tokyo Peil), which was determined by the tidal records at Tokyo Bay during the period between 1873 and 1879, and corresponds to the mean water level in the bay.

Additional information

Funding

This work was supported by the Japan Science and Technology Agency [JPMJBF2005]; Japan Society for the Promotion of Science [JP19K24677]; Japan Society for the Promotion of Science [JP20KK0107]; Japan Society for the Promotion of Science [JP21J20393].