Combined effects of coastal forest and sea embankment on reducing the washout region of houses in the Great East Japan tsunami

Tanaka, Norio; Yasuda, Satoshi; Iimura, Kosuke; Yagisawa, Junji

doi:10.1016/j.jher.2013.10.001

Cited by 76 publications

(28 citation statements)

References 27 publications

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“…Moreover, the Froude number at the coast is assumed to be larger than 1 because the value of Eq. (16) is around 2 maximum (Tanaka et al, 2014); thus, velocity head and energy head for the sea embankment may be larger than that shown in Fig. 9b.…”

Section: Relationship Between Characteristics Of Scoured Region and Tmentioning

confidence: 75%

“…The maximum tsunami water depth on the embankment could not be measured, but the tsunami mark near this region was 6 m in our investigation, and in the 5-10 m range measured by TETJSG (2012) near the embankment. The coastal forest on the sand dune could increase the water depth by its drag (Tanaka et al, 2014), so the overtopping type may be the submerged type when the tsunami water depth was at its maximum although the overflow was the free type when the overflow began. Thus, we classified the scoured region as the 'submerged type'.…”

Section: Site Locations and Measurement Methodsmentioning

confidence: 99%

“…2. C d values for houses and trees were changed after breaking or washout using the method of Tanaka et al (2014) and Thuy et al (2012).…”

Section: Differential Equationsmentioning

confidence: 99%

“…One of the mechanisms of the embankment failure observed was scouring of the substrate supporting the structures. The presence or breaching of a sea embankment greatly affected the damage to coastal forests and wooden buildings in the Sendai area (Tanaka, 2012;Tanaka et al, 2012Tanaka et al, , 2014. Bricker et al (2012) and Tokida and Tanimoto (2012) conducted post-tsunami surveys and investigated the scoured depth around coastal structures.…”

Section: Introductionmentioning

confidence: 99%

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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

Tanaka

Sato

2015

Ocean Engineering

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Section: Relationship Between Characteristics Of Scoured Region and Tmentioning

confidence: 75%

Section: Site Locations and Measurement Methodsmentioning

confidence: 99%

“…2. C d values for houses and trees were changed after breaking or washout using the method of Tanaka et al (2014) and Thuy et al (2012).…”

Section: Differential Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Tanaka

Sato

2015

Ocean Engineering

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“…Thus, it was found that the average flow velocity over the beach was 6.2 m/s, resulting in Froude number values of 1.14-1.4 (Nandasena et al 2012). Tanaka et al (2014) reported that 210 m from the shoreline, the Froude number is 1.5. The velocity observed in this field study, 6.26 m/s, yields Froude numbers of \1.…”

Section: Discussionmentioning

confidence: 99%

Field study on planted forest structures and their role in protecting communities against tsunamis: experiences along the coast of the Biobío Region, Chile

et al. 2015

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A field study using satellite images was carried out to analyze the effect of coastal vegetation in mitigating the impact of a catastrophic tsunami on coastal villages in the Biobío Region, Chile, in February 2010. Two types of stand, Pinus radiata D. Don forests and Cupressus macrocarpa Hartw. shelterbelts, appear to have protected coastal areas behind them from the direct impact of the tsunami. The impacts of the horizontal and vertical structures of these coastal forests on the drag forces were analyzed by observing the characteristics of Pinus radiata forests and Cupressus macrocarpa shelterbelts. The stands absorbed the impact of the tsunami without incurring broken stems or uprooted trees due to their diverse horizontal structure, as they contained short trees with various diameters. However, small areas of the stands were damaged by salinity after the tsunami. For this tsunami, which was less than 3 m high, the horizontal and vertical structures of the P. radiata and C. macrocarpa stands provided effective protection for coastal villages since they reduced the velocity and height of the tsunami. A shelterbelt consisting of three rows of C. macrocarpa in front of the tsunami and a P. radiata forest with a density of 11 trees/100 m 2 and a width of[50 m immediately behind the shelterbelt are suggested as a means of protecting communities along the coastline of the Biobío Region against tsunamis.

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Experimental investigation of flood energy reduction through vegetation at various angles

Ahmed

Valyrakis

Ghumman

et al. 2021

River Research & Apps

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The efficiency of flow energy reduction past emergent vegetation has been typically studied assuming a right angle of the vegetated corridor to the flow direction. However, in many real-world cases the riparian zones of natural, restored, or engineered rivers and waterways, are found at an oblique angle to the flood flow direction. In the current study, the effect of vegetation angle with respect to the flow direction is investigated experimentally in an open channel rectangular flume. The experiments are conducted under a range of subcritical steady flow conditions, with varying Froude number (Fr o ). The vegetation cover is placed at various angles to the flow direction (90 , 45 , and 30 ), for a sparse and intermediate vegetation density, defined from the ratio of spacing of each vegetation element in the cross stream direction (B), and the diameter of vegetation element (d) (B/d = 2.13 and 1.09, respectively). Detailed water surface profiles are obtained for all those cases, demonstrating a considerable backwater rise, increasing with increasing vegetation density, Froude number, and flow approach angle. The energy reduction decreased by increasing the Froude number for the perpendicular (90 ) and increased for oblique vegetation (45 and 30 ). For the perpendicular vegetation, the average energy reduction rate for sparse (90VS) and intermediate (90VI) vegetation densities are 25.44% and 31.44%, respectively. The range of average energy reduction for sparse vegetation at 45 (45VS) and at 30 (30VS) are 18.3-19.8% and 18.7-19.7%, respectively. Similarly, range of average energy reduction for intermediate vegetation at 45 (45VI) and at 30 (30VI) are 21.4-22% and 18.8-22%, respectively.

show abstract

Combined effects of coastal forest and sea embankment on reducing the washout region of houses in the Great East Japan tsunami

Cited by 76 publications

References 27 publications

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

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

Field study on planted forest structures and their role in protecting communities against tsunamis: experiences along the coast of the Biobío Region, Chile

Experimental investigation of flood energy reduction through vegetation at various angles

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