Levee damage and bridge scour by 2019 typhoon Hagibis in Kanto Region, Japan

• Published in: Soils and foundations 2021-04, Vol.61 (2), p.566-585
• Main Authors: Enomoto, Tadao, Horikoshi, Kazuki, Ishikawa, Keisuke, Mori, Hirotoshi, Takahashi, Akihiro, Unno, Toshiyasu, Watanabe, Kenji
• Format: Article
• Language: English
• Subjects: Bridge scour; Inland flooding; Levee breach; Overtopping; Typhoon Hagibis
• ISSN: 0038-0806
• DOI: 10.1016/j.sandf.2021.01.007

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.