Akira Kanemura

Characterization of tidal wave disaster occurrence in the inner part of Toyama Bay

Naoyuki Inukai

Typhoon No. 19 in 2019 caused damage due to high waves near Toyama Bay. Previous research by this research group has revealed wave characteristics in the waters surrounding Niigata Prefecture. The objective of this study was to understand the conditions of high waves in Toyama Bay in order to make it easier for field workers to predict high waves in the bay.
First, the paths of typhoons and cyclones that have approached Japan in the past were investigated from weather maps published by the Japan Meteorological Agency. The paths of typhoons and cyclones approaching Japan were roughly classified into five patterns, and the paths of typhoons and cyclones at the time of high waves in Toyama Bay were determined. As a result, it was found that the most caution is required when the typhoon/low pressure system moves northeastward over the Kanto region. 
Next, in order to evaluate the magnitude of typhoons and cyclones, the pressure gradient in Toyama Bay was calculated and its relationship with the significant wave height was investigated. As a result, there was a tendency for significant wave heights to increase as the pressure gradient increased. In addition, wind direction in Toyama Bay was also investigated, and it was found that when significant wave height increases in Toyama Bay, the pressure gradient is greater than 0.02 hPa/km, the wind direction is NE or NNE, and a typhoon or low pressure system moves northeastward over the Kanto region. 
The wind speed and distance of the wind blowing into Toyama Bay were determined, and the SMB method was used to estimate the significant wave height. As a result, it was found that the period is not easy to be periodic and the wave height tends to increase in Toyama Bay. A further contributing factor is the high wind speed and short blow-off distance.