Typhoon Hagibis made landfall in Japan at 19:00 JST on 12th October 2019. The heavy rainfall caused by the typhoon was mostly concentrated within a 24-hour period; it brought devastating damage to eastern Japan. This report focuses on the flood-induced levee damage and bridge scour generated by the typhoon in the Kanto region. The levee breaches occurred mainly in the northern part of the region. They were concentrated along the Kuji and Naka Rivers and tributaries of the Tone and Arakawa Rivers. In most breached locations, the cause of the damage was the landward overtopping of the river water. Surface erosion on the slope of the protected side and/or slope failure on the protected side due to seepage-induced instability were the main causes of the levee breaches. Apart from the flooding induced by the inundation of the river water, inland flooding was also found. Damage to a river bridge due to local scour revealed the importance of considering the movement of sandbars in river channels, i.e., changes in the river flow conditions, when assessing the risks of bridge scour.

台风哈吉比斯于2019年10月12日19:00 JST在日本登陆。它给日本东部带来了毁灭性的破坏。本报告的重点是关东地区台风造成的洪水引发的堤防破坏和桥梁冲刷。堤防违规事件主要发生在该地区的北部。它们集中在久慈河和中河以及通河和荒川河的支流上。在大多数被破坏的地方，造成破坏的原因是河水向地面过度倾斜。堤防破坏的主要原因是受保护侧边坡的表面侵蚀和/或受渗流引起的不稳定性引起的受保护边坡的破坏。除了河水泛滥引起的洪水外，内陆洪水也被发现。因局部冲刷而对河桥造成的破坏表明，在评估桥梁冲刷风险时，必须考虑沙洲在河道中的运动，即河流流量条件的变化，这一点很重要。