Numerical Investigation of the Effectiveness of Vegetation-Embankment Hybrid Structures for Tsunami Mitigation Introduced after the 2011 Tsunami

As a mitigation measure against a tsunami inundation, vegetation-embankment hybrid structures received attention after the 2011 Great East Japan Tsunami, and some structures have already been constructed or are under construction in Japan. The present study conducted a series of numerical simulation...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autores principales:	Norio Tanaka, Yoshiya Igarashi, Takehito Zaha
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	vegetation resistance hybrid structures tsunami mitigation fluid force back-water rise Geology QE1-996.5
Acceso en línea:	https://doaj.org/article/59cceb0572b34942b92ecaeb00e16ae9
Etiquetas:	Agregar Etiqueta Sin Etiquetas, Sea el primero en etiquetar este registro!

id	oai:doaj.org-article:59cceb0572b34942b92ecaeb00e16ae9
record_format	dspace
spelling	oai:doaj.org-article:59cceb0572b34942b92ecaeb00e16ae92021-11-25T17:42:43ZNumerical Investigation of the Effectiveness of Vegetation-Embankment Hybrid Structures for Tsunami Mitigation Introduced after the 2011 Tsunami10.3390/geosciences111104402076-3263https://doaj.org/article/59cceb0572b34942b92ecaeb00e16ae92021-10-01T00:00:00Zhttps://www.mdpi.com/2076-3263/11/11/440https://doaj.org/toc/2076-3263As a mitigation measure against a tsunami inundation, vegetation-embankment hybrid structures received attention after the 2011 Great East Japan Tsunami, and some structures have already been constructed or are under construction in Japan. The present study conducted a series of numerical simulations using a hybrid system comprised of an artificial structure (an embankment, moat) and a natural component (vegetation) that was experimentally proposed in previous studies as an effective structure for tsunami mitigation. After validating the numerical model using published data, this study investigated differences in the performance of the hybrid system by changing the tsunami period and height characteristics of the tsunami-like surge-type flow. As a result, the delay in tsunami arrival time (ΔT) was not affected by the tsunami wave period for the investigated hybrid structures. Among the investigated structures, Case Ve<sub>40</sub>ME (where Ve<sub>40,</sub> M, and E represent vegetation, moat, and embankment, respectively, in that order from seaward) showed the maximum performance of ΔT. The reductions of overflow volume (ΔQ), fluid force index (RFI), and moment index (RMI) declined during the tsunami period. The tsunami mitigation effect is closely related to the relationship between the development times of backwater rise, hydraulic jump, and the tsunami period. Case Ve<sub>40</sub>ME was effective for ΔT, ΔQ, and RMI. Case EMVe<sub>40</sub> was especially effective for RFI. When the tsunami period is short, the water level at the shoreline starts to decrease before full development of the hydraulic jump generated in the hybrid system. Thus, overflow volume to landward decreases, and the mitigation effects increase. When the tsunami period is long, the receding phenomenon at the peak water level does not affect the maximum values, thus the mitigation effects become smaller compared with the short period. However, the superiority to other structures is maintained in Case Ve<sub>40</sub>ME and Case EMVe<sub>40</sub> with seaward vegetation and landward vegetation, respectively.Norio TanakaYoshiya IgarashiTakehito ZahaMDPI AGarticlevegetation resistancehybrid structurestsunami mitigationfluid forceback-water riseGeologyQE1-996.5ENGeosciences, Vol 11, Iss 440, p 440 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	vegetation resistance hybrid structures tsunami mitigation fluid force back-water rise Geology QE1-996.5
spellingShingle	vegetation resistance hybrid structures tsunami mitigation fluid force back-water rise Geology QE1-996.5 Norio Tanaka Yoshiya Igarashi Takehito Zaha Numerical Investigation of the Effectiveness of Vegetation-Embankment Hybrid Structures for Tsunami Mitigation Introduced after the 2011 Tsunami
description	As a mitigation measure against a tsunami inundation, vegetation-embankment hybrid structures received attention after the 2011 Great East Japan Tsunami, and some structures have already been constructed or are under construction in Japan. The present study conducted a series of numerical simulations using a hybrid system comprised of an artificial structure (an embankment, moat) and a natural component (vegetation) that was experimentally proposed in previous studies as an effective structure for tsunami mitigation. After validating the numerical model using published data, this study investigated differences in the performance of the hybrid system by changing the tsunami period and height characteristics of the tsunami-like surge-type flow. As a result, the delay in tsunami arrival time (ΔT) was not affected by the tsunami wave period for the investigated hybrid structures. Among the investigated structures, Case Ve<sub>40</sub>ME (where Ve<sub>40,</sub> M, and E represent vegetation, moat, and embankment, respectively, in that order from seaward) showed the maximum performance of ΔT. The reductions of overflow volume (ΔQ), fluid force index (RFI), and moment index (RMI) declined during the tsunami period. The tsunami mitigation effect is closely related to the relationship between the development times of backwater rise, hydraulic jump, and the tsunami period. Case Ve<sub>40</sub>ME was effective for ΔT, ΔQ, and RMI. Case EMVe<sub>40</sub> was especially effective for RFI. When the tsunami period is short, the water level at the shoreline starts to decrease before full development of the hydraulic jump generated in the hybrid system. Thus, overflow volume to landward decreases, and the mitigation effects increase. When the tsunami period is long, the receding phenomenon at the peak water level does not affect the maximum values, thus the mitigation effects become smaller compared with the short period. However, the superiority to other structures is maintained in Case Ve<sub>40</sub>ME and Case EMVe<sub>40</sub> with seaward vegetation and landward vegetation, respectively.
format	article
author	Norio Tanaka Yoshiya Igarashi Takehito Zaha
author_facet	Norio Tanaka Yoshiya Igarashi Takehito Zaha
author_sort	Norio Tanaka
title	Numerical Investigation of the Effectiveness of Vegetation-Embankment Hybrid Structures for Tsunami Mitigation Introduced after the 2011 Tsunami
title_short	Numerical Investigation of the Effectiveness of Vegetation-Embankment Hybrid Structures for Tsunami Mitigation Introduced after the 2011 Tsunami
title_full	Numerical Investigation of the Effectiveness of Vegetation-Embankment Hybrid Structures for Tsunami Mitigation Introduced after the 2011 Tsunami
title_fullStr	Numerical Investigation of the Effectiveness of Vegetation-Embankment Hybrid Structures for Tsunami Mitigation Introduced after the 2011 Tsunami
title_full_unstemmed	Numerical Investigation of the Effectiveness of Vegetation-Embankment Hybrid Structures for Tsunami Mitigation Introduced after the 2011 Tsunami
title_sort	numerical investigation of the effectiveness of vegetation-embankment hybrid structures for tsunami mitigation introduced after the 2011 tsunami
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/59cceb0572b34942b92ecaeb00e16ae9
work_keys_str_mv	AT noriotanaka numericalinvestigationoftheeffectivenessofvegetationembankmenthybridstructuresfortsunamimitigationintroducedafterthe2011tsunami AT yoshiyaigarashi numericalinvestigationoftheeffectivenessofvegetationembankmenthybridstructuresfortsunamimitigationintroducedafterthe2011tsunami AT takehitozaha numericalinvestigationoftheeffectivenessofvegetationembankmenthybridstructuresfortsunamimitigationintroducedafterthe2011tsunami
_version_	1718412105407791104

Numerical Investigation of the Effectiveness of Vegetation-Embankment Hybrid Structures for Tsunami Mitigation Introduced after the 2011 Tsunami

Ejemplares similares