ABSTRACT

The 2011 Great East Japan Earthquake and Tsunami are one of the most catastrophic natural disasters that took place in Japan. The disaster caused widespread destruction to the estuarine and coastal areas along the northeastern region of Japan. The Abukuma River mouth, among many estuaries in Miyagi Prefecture, suffered major damage from the tsunami in which the sand spit and the sand terrace were severely eroded. The present study aims to provide a better comprehension of the morphology of the Abukuma River mouth within a decade after the 2011 tsunami based on the collected datasets of imagery and offshore bathymetry surveys. The consecutive changes of the sand terrace and sand spit indicate their connection influencing the morphological recovery in the Abukuma River mouth. About a year after the tsunami, the sand terrace re-appeared by a flood event and became the sediment source to recover the sand spit under the intrusion process. When the sand spit almost recovered and achieved a stable configuration, the sediment from the sand terrace into the river was restricted. As a result, more sediment from the sand terrace was expected to be transported to the downdrift area under the dominant wave condition in the Abukuma River mouth.

摘要

2011 年东日本大地震和海啸是日本发生的最具灾难性的自然灾害之一。这场灾难对日本东北地区的河口和沿海地区造成了广泛的破坏。宫城县众多河口中的阿武隈川河口在海啸中遭受了重大破坏，沙尘和沙阶被严重侵蚀。本研究旨在根据收集的图像和近海测深调查数据集，在 2011 年海啸后的十年内更好地了解阿武库马河河口的形态。沙阶和沙嘴的连续变化表明它们之间的联系影响了阿武隈河河口的形态恢复。海啸发生大约一年后，沙地阶地因洪水事件重新出现，成为在入侵过程中回收沙子的沉积源。当沙子几乎恢复并达到稳定形态时，沙子阶地进入河流的沉积物受到限制。因此，在阿布库马河河口占主导地位的波浪条件下，预计更多的沙质阶地沉积物将被输送到下漂区。