ABSTRACT The extreme typhoon Lan caused devastating damage to the Seisho Coast of Japan in 2017. This study presents nearshore wave measurements conducted at different locations along the shore and numerical hindcasts to elucidate the extreme wave field during the typhoon focusing on infragravity wave dynamics, which was comparable in magnitude to incident short waves in shallow water. During the peak of the typhoon, there was a significant wave height of ~8 m, and the infragravity wave height exceeded 2 m at a 14 m depth. The measurement data suggest that infragravity waves developed as bound waves from incident wave groups and partially dissipated during the typhoon peak in the surf and swash zones through their energy transfer to high-frequency waves. Numerical wave hindcasting models successfully reproduced the measured extreme wave field and indicated that the wave refraction over Oiso Spur caused an incident wave concentration in the severely damaged area where high waves collapsed a seawall during the typhoon. Moreover, infragravity waves also exhibited significant alongshore variation, which was due to the different bottom slopes and incident short-wave properties. This study identifies several key features that may have caused the localization of significant damage along the Seisho Coast.

中文翻译：

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2017年兰台风期间西正海岸的次重力波动力学

摘要 2017 年极端台风 Lan 对日本 Seisho 海岸造成毁灭性破坏。本研究介绍了在海岸不同位置进行的近岸波测量和数值后报，以阐明台风期间的极端波场，重点关注次重力波动力学，这是在幅度上与浅水中的入射短波相当。在台风高峰期，有～8 m的显着波高，在14 m深度处的次重力波高超过2 m。测量数据表明，次重力波是作为入射波群的束缚波发展起来的，并在海浪和冲刷区的台风高峰期通过它们的能量转移到高频波而部分消散。数值波浪后报模型成功地再现了测量到的极端波场，并表明在大矶 Spur 上的波浪折射在台风期间高波使海堤坍塌的严重受损区域引起了入射波集中。此外，由于不同的底坡和入射短波特性，次重力波也表现出显着的沿岸变化。这项研究确定了可能导致 Seisho 海岸发生重大破坏的几个关键特征。这是由于不同的底坡和入射短波特性造成的。这项研究确定了可能导致 Seisho 海岸发生重大破坏的几个关键特征。这是由于不同的底坡和入射短波特性造成的。这项研究确定了可能导致 Seisho 海岸发生重大破坏的几个关键特征。