Experiments on local scour behind coastal dikes induced by Tsunami overflow

Yuta Mitobe, Mohammad Bagus Adityawan, Hitoshi Tanaka, Toshiya Kawahara, Tatsuaki Kurosawa, Kazutaka Otsushi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Citations (Scopus)

Abstract

A lot of coastal dikes located along the Pacific Coast of Tohoku Region were severely damaged by the Great East Japan Earthquake Tsunami. In this study, hydraulic model experiments were conducted to understand characteristics of local scour at a landward toe of a coastal dike, which has been considered as a main cause of the failures of coastal dikes by the 2011 tsunami. A coastal dike model is fixed in a horizontal open channel with 4.5m length. Scouring of sandy bed behind the dike model under constant discharge is recorded by a video camera and temporal variations of sizes of the scour hole are extracted from the video images. In the experiments, two types of flow patterns, flow with hydraulic jump and submerged flow, were observed around the toe and it is found that the different flow types induce completely different processes of the local scouring, resulting in significant differences of scouring depths. Embedment of the landward toe induced the submerged-type flow to form deeper scour holes than those with a basic model of the toe without embedment. On the other hand, sheet-pile structure is found to be an effective measure against local scouring to delay start of suction of sand under the landward slope through the scour hole.

Original languageEnglish
Title of host publicationProceedings of the 34th International Conference on Coastal Engineering, ICCE 2014
EditorsPatrick Lynett
PublisherAmerican Society of Civil Engineers (ASCE)
ISBN (Electronic)9780989661126
Publication statusPublished - 2014 Jan 1
Event34th International Conference on Coastal Engineering, ICCE 2014 - Seoul, Korea, Republic of
Duration: 2014 Jun 152014 Jun 20

Publication series

NameProceedings of the Coastal Engineering Conference
Volume2014-January
ISSN (Print)0161-3782

Other

Other34th International Conference on Coastal Engineering, ICCE 2014
Country/TerritoryKorea, Republic of
CitySeoul
Period14/6/1514/6/20

Keywords

  • Coastal dikes
  • Hydraulic jump
  • Local scour
  • Tsunami overflow

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Ocean Engineering
  • Oceanography

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