Coastal destruction and unusual wave spectra induced by Typhoon Faxai in 2019

Abstract

Typhoon Faxai (T1915), which occurred in September 2019, was one of the strongest typhoons on record to make landfall in the Tokyo metropolitan area and it caused extensive damage along the coast in Tokyo Bay. Two intriguing phenomena are reported by a post-event survey, which motivated this study. The first is that although the storm impacted the whole bay, significant damage was concentrated in a small area near the Port of Yokohama. The second is about the direction of the hazardous waves, which came from both the northeast and the southeast. The underlying wave dynamics that lead to these events were unknown. Here, we elucidate characteristics of the waves incident to the Port of Yokohama that caused a concentration of severe damage, and we clarify the mechanism responsible for the two disparate wave directions observed. We found that the development of wind waves under slanting fetch conditions and the refraction of the swell by the Tokyo Submarine Canyon were key factors for generating unusual coastal wave spectra. Our results also demonstrate that the maximum wave power is a good indicator for the location of coastal damage.