National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
Graduate School of Agricultural Science, Kobe University, Nada-ku, Kobe-shi, Hyogo, Japan.
PLoS One. 2023 Oct 13;18(10):e0292930. doi: 10.1371/journal.pone.0292930. eCollection 2023.
Coastal dikes are an essential social infrastructure to mitigate tsunami damage. However, there are no clear guidelines on effective dike shapes for reducing tsunami overflow. To examine effective dike shapes, numerical simulations of the amount of tsunami overflow at coastal dikes are conducted with reference to tsunami waveforms caused by the Great East Japan Earthquake. Results reveal the relationship between the dike shape and the amount of the overflow; the mechanism of overflow reduction based on the velocity and water level distribution is also verified. The comparison of the seaward and landward slopes of coastal dikes reveals that the seaward slope has a greater impact on the overflow, and the seaward slope with a vertical wall or a wave return structure reduces the overflow by 5%-30% compared to the 1:2 (26.6°) seaward slope. The landward slope should be determined based on the tsunami scale and the scour related to the dike stability. Since tsunami inflow damages human life and social infrastructure, achieving the overflow reduction without increasing dike height is vital. Our work contributes to rational design guidelines for coastal dikes.
海堤是减轻海啸破坏的重要社会基础设施。然而，对于减少海啸溢流水量的有效海堤形状，目前尚无明确的指导方针。为了研究有效海堤形状，参考东日本大地震引发的海啸波，对海堤的海啸溢流水量进行了数值模拟。结果揭示了海堤形状与溢流水量之间的关系；还验证了基于流速和水位分布的溢流水量减少的机制。对海堤的向海和向陆坡度进行了比较，结果表明，向海坡度对溢流水量的影响更大，与 1:2（26.6°）向海坡度相比，垂直墙或波浪返回结构的向海坡度可减少 5%-30%的溢流水量。向陆坡度应根据海啸规模和与海堤稳定性有关的冲刷来确定。由于海啸涌入会对人类生命和社会基础设施造成损害，因此在不增加海堤高度的情况下实现溢流水量减少至关重要。我们的工作为海堤的合理设计指南做出了贡献。
