Scoured depth and length of pools and ditches generated by overtopping flow from embankments during the 2011 Great East Japan Tsunami

Tanaka, Norio; Sato, Masayuki

doi:10.1016/j.oceaneng.2015.08.053

Cited by 31 publications

(10 citation statements)

References 30 publications

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“…Estimated processes of the failures of the coastal embankments by 2011 Tohoku Tsunami were discussed through the field observations by Kato et al [2013]. One of the main process of the failure is from the local scour around the landward toes of the coastal embankments, which were observed also by Tappin et al [2012], Tanaka and Sato [2015]. Ground near their landward toes was eroded severely by the flow over the embankments and sand under their concrete armors (as body material of the coastal embankments) was sucked out through the huge scours, leading to breaking of the concrete armors of landward slopes and finally complete flushing of the embankments themselves.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Embankment Reinforcement by Steel Sheet Pile Structure Against Tsunami Overflow

Mitobe

Adityawan

Roh³

et al. 2016

Coastal Engineering Journal

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This study proposes a new embankment reinforcement using steel sheet piles against tsunami overflow, which has been known as the main cause of the failures of the embankments by the 2011 Tohoku Earthquake Tsunami. Effectiveness of the proposed technique was discussed through a hydraulic experiment. A model of embankment was set in a horizontal open channel, and one or two steel plates are installed into the embankment from the top as vertical walls inside. Temporal variations of the shapes of the embankment and the sheet pile structures were obtained from video images. In most of the cases, the sheet pile structures started to rotate after the erosion of the landward slope of the embankment. However the rotation stopped at about 30° and 10° from the initial location with the single-and double-wall cases. Height of the embankment after overflow was less than 20% with no reinforcement, while more than 70% and 95% of the height were kept with the single-and double-wall structures, respectively. The performance of the embankment with the reinforcement was also discussed in terms of tsunami energy reduction with an additional fixed-bed experiment.

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Section: Introductionmentioning

confidence: 99%

Experimental Study on Embankment Reinforcement by Steel Sheet Pile Structure Against Tsunami Overflow

Mitobe

Adityawan

Roh³

et al. 2016

Coastal Engineering Journal

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“…To compare the effectiveness of DLMs (L2 with different porosities of L1), SLM (no L1) with a porosity of 0.98 was also implemented. In the 2011 GEJT, severe erosion occurred behind the embankments due to the overtopping tsunami, and the length of scouring varied from 4 to 31.78 (m) [16,39]. The length and depth of the scouring increased while increasing the momentum and energy head of the overtopping tsunami [39].…”

Section: Physical Model Of the Hybrid Defense Systemmentioning

confidence: 99%

“…In the 2011 GEJT, severe erosion occurred behind the embankments due to the overtopping tsunami, and the length of scouring varied from 4 to 31.78 (m) [16,39]. The length and depth of the scouring increased while increasing the momentum and energy head of the overtopping tsunami [39]. The study also observed that the trees that had been planted closer to the embankment on the leeward side were uprooted and produced floating debris, whereas a costal forest having no gap between the coastal dike and forest was completely damaged by the overtopping tsunami [16].…”

Section: Physical Model Of the Hybrid Defense Systemmentioning

confidence: 99%

“…When a tsunami overtops a high embankment, the higher angle of attack with a higher flow velocity carries it downstream, which causes damage to the downstream structures as well as erosion around the toe of the embankment. Due to this, coastal structures were damaged severely, and houses and trees behind the embankment were destroyed in the GEJT [39,50]. Following the massive destruction by the GEJT, a new system of coastal structures was planned under the guidelines of the National Institute for Land and Infrastructure Management (NILIM), Japan.…”

Section: Changes In Flow Structure In the Hybrid Defense Systemmentioning

confidence: 99%

“…The elevated water head then overtops the mitigation structure and collides with the ground of the embankment toe at a high angle of attack and flow energy, which causes scouring and erosion around the defense structure. Due to this, large embankments were destroyed in the 2011 Japan tsunami [3][4][5]39,50,53]. During the tsunami, destruction of houses and buildings was extensive and large areas of coastal and inland forests were damaged where the embankments were eroded and/or damaged [15].…”

Section: Control Of Scouring To Reduce the Destruction Of Defense Strmentioning

confidence: 99%

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Energy Reduction of a Tsunami Current through a Hybrid Defense System Comprising a Sea Embankment Followed by a Coastal Forest

Muhammad

Tanaka

2019

Geosciences

Self Cite

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The 2011 Great East Japan tsunami revealed the limit of using natural or artificial infrastructures as a single tsunami countermeasure. In recent tsunami mitigation strategy, interest in a hybrid defense system (combination of natural and artificial infrastructures) rather than a single defense structure is growing, and a pilot project has already started in Japan. Clarification of flow structures within the hybrid defense system is necessary for designing an improved mitigation system. In addition, when a hydraulic jump is expected, its position should be restricted to a protected area for the resilience of the hybrid defense system. This study performed flume tests to elucidate the mitigation effect of a hybrid defense system comprising an embankment model (EM), followed by different types of single-layer emergent forest models (SLM) or vertical double-layer forest models (DLM). Different types of hydraulic jumps were observed within the defense system, jump position and their characteristics dominated the energy reduction downstream of SLM or DLM. Experimental results showed that this hybrid defense system reduced the flow energy to 30% and 40% of maximum for SLM and DLM, respectively, compared to only the single EM. Moreover, the position of the hydraulic jump was near the EM in the combination of EM and DLMs.

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Study of Coastal Morphology Changes Due to Tsunami in the Sunda Megathrust—A Case Study at Pelabuhan Ratu Bay

Kurniawan,

Malakani,

Pratama

et al. 2024

Advanced Structured Materials

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Scoured depth and length of pools and ditches generated by overtopping flow from embankments during the 2011 Great East Japan Tsunami

Cited by 31 publications

References 30 publications

Experimental Study on Embankment Reinforcement by Steel Sheet Pile Structure Against Tsunami Overflow

Experimental Study on Embankment Reinforcement by Steel Sheet Pile Structure Against Tsunami Overflow

Energy Reduction of a Tsunami Current through a Hybrid Defense System Comprising a Sea Embankment Followed by a Coastal Forest

Study of Coastal Morphology Changes Due to Tsunami in the Sunda Megathrust—A Case Study at Pelabuhan Ratu Bay

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