EFFECTS OF TYPHOON FORWARD SPEED TO STORM SURGE WITH WAVE-INDUCED SETUP: CASE STUDY OF 2018 TYPHOON JEBI AT HIDAKA PORT, JAPAN

Abstract

 We investigated the relationship between the forward speed of a typhoon and wave-induced setup at Hidaka Bay, Wakayama Prefecture, where a remarkable storm surge caused by 2018 typhoon Jebi was observed. The storm surge hindcast was carried out by the ocean-wave coupled model (COAWST), and showed that the maximum storm surge (1.7 m) at the bay was mainly due to wave-induced setup (above 1.2 m). It also maintained the surge height up to 0.5 m for several hours after passing the typhoon, which did not reproduce well by the ocean model alone. Furthermore, we conducted numerical experiments and revealed that when the forward speed exceeded the group velocity of waves, the maximum significant wave height decreased significantly (below -4.0 m) compared to when the forward speed was close to the group velocity. Due to this reduction, the wave-induced setup was being smaller by nearly 1.0 m.