Numerical Simulation of Storm Surges and Waves Caused by Typhoon Jebi in Osaka Bay with Consideration of Sudden Change of Wind Field

Abstract

Typhoon Jebi (T1821) was a high-speed typhoon with a moving speed exceeding 60 km/h at landfall, and with a further acceleration of the moving speed just before 14:00 on September 4, 2018, formed an extremely strong wind field, causing a storm surge and high wave disasters along the northern coast of Osaka Bay. This study conducted a numerical simulation of storm surges and waves using the wave-surge combined numerical model taking the effects of moving speed acceleration into consideration by enhancing the JMA GPV wind data. The computation successfully reproduced the disaster external forces in Kobe and Osaka Ports, Yodo River mouth, and Kansai International Airport. The major findings of the study are summarized as follows: (1) Numerical analysis considering the rapid increase of surface wind due to acceleration of the typhoon moving speed reproduced the storm surge anomaly exceeding 2.77 m observed at the northern end of Osaka Bay. (2) The storm surge water level in Yodo River exceeding O.P.+5.2 m was also reproduced. (3) The computed total water level was CDL+4.16 m (storm surge + wave run-up height + margin height) on the southeast side of Kansai International Airport Island that exceeded the current crown height of CDL+3.9 m.

A new tropical cyclone surge index incorporating the effects of coastal geometry, bathymetry and storm information

“…The observed peak surge for Jebi is 161 cm (at Osaka). In the case of Jebi, surge was largely contributed to by high waves [64][65][66] , which is not considered in the SSHPI. The SSHPI also underestimates the observed value of Tokage in 2004.…”

A new tropical cyclone surge index incorporating the effects of coastal geometry, bathymetry and storm information

“…The observed maximum surge for Jebi is 161 cm (at Osaka). In the case of Jebi, surge was largely contributed to by high waves [63][64][65] , which is not considered in the SSHPI. The SSHPI also underestimates the observed value of Tokage in 2004.…”