Effects of Sand Dune and Vegetation in the Coastal Area of Sri Lanka at the Indian Ocean Tsunami

Tanaka, Norio; Sasaki, Yasushi; Mowjood, M. I. M.

doi:10.1142/9789812708915_0015

Cited by 17 publications

(21 citation statements)

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“…This island disappeared during the 1979 tsunami but played a protective role during the event by substantially reducing the scale of the disaster. The tsunami experience in Indonesia showed that there are natural structures, such as beaches, dunes, mangroves, coral fields or groves, that help to significantly mitigate the effects of tsunamis (Tanaka et al, 2006(Tanaka et al, , 2007Tanaka, 2009). …”

Section: J Otero Et Al: Tsunami Hazard Assessment In the Southermentioning

confidence: 99%

Tsunami hazard assessment in the southern Colombian Pacific basin and a proposal to regenerate a previous barrier island as protection

Díaz

Restrepo

González

2014

Nat. Hazards Earth Syst. Sci.

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Abstract. In this study, the tsunami hazard posed to 120 000 inhabitants of Tumaco (Colombia) is assessed, and an evaluation and analysis of regenerating the previous El Guano Island for tsunami protection is conducted. El Guano Island was a sandy barrier island in front of the city of Tumaco until its disappearance during the tsunami of 1979; the island is believed to have played a protective role, substantially reducing the scale of the disaster. The analysis is conducted by identifying seismotectonic parameters and focal mechanisms of tsunami generation in the area, determining seven potential generation sources, applying a numerical model for tsunami generation and propagation, and evaluating the effect of tsunamis on Tumaco. The results show that in the current situation, this area is vulnerable to impact and flooding by tsunamis originating nearby. El Guano Island was found to markedly reduce flood levels and the energy flux of tsunami waves in Tumaco during the 1979 tsunami. By reducing the risk of flooding due to tsunamis, the regeneration and morphological modification of El Guano Island would help to protect Tumaco.

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Section: J Otero Et Al: Tsunami Hazard Assessment In the Southermentioning

confidence: 99%

Tsunami hazard assessment in the southern Colombian Pacific basin and a proposal to regenerate a previous barrier island as protection

Díaz

Restrepo

González

2014

Nat. Hazards Earth Syst. Sci.

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“…2.2 Effects of forest density, tree-trunk diameter, and stand structure of trees Field surveys in Sri Lanka and Thailand after the Indian Ocean tsunami showed that older (larger diameter) Casuarina equisetifolia belts on the coast withstood the tsunami but failed to provide good protection (Tanaka et al, 2006a(Tanaka et al, , 2006b. showed that tree growth and forest density can have a significant effect on tsunami mitigation because trees with larger trunk diameters require more space (lower tree density) between them to grow.…”

Section: Effectiveness Of Coastal Forests In Tsunami Mitigationmentioning

confidence: 99%

“…Considering the other roles, i.e. trapping debris and providing something to climb to escape or a soft-landing place for people, that coastal vegetation plays (Shuto, 1987;Tanaka et al 2006b, a two-layer forest of P. odoratissimus and dense C. equisetifolia should be planted and preserved near the coast, and other broad-leaved trees should be grown behind this buffer forest (towards inland), as shown in Fig. 3 .…”

Section: Effectiveness Of Coastal Forests In Tsunami Mitigationmentioning

confidence: 99%

“…8(b),(d)). Tanaka et al (2006bTanaka et al ( , 2008b conducted tree breaking tests in situ using small diameter trunks or branches and showed that the breaking moment curve of representative tree species (Fig.9) can be classified into three parts by elasticity and habitat as 1. the curve for coastal vegetation (ex. P. odoratissimus), 2. the curve for elastic trees 3. the curve for trees with hard trunks (ex.…”

Section: Effectiveness Of Coastal Forests In Tsunami Mitigationmentioning

confidence: 99%

“…This indicates that the breaking condition is not well expressed by the breaking test using C. equisetifolia with small trunk diameters. Further study of the breaking or uprooting conditions for C. equisetifolia is recommended with realscale breaking or uprooting tests like those of Peltola et al (2000) because C. equisetifolia is expected to be an effective species for dissipating tsunami energy in Sri Lanka, Thailand (Tanaka et al, 2006a(Tanaka et al, , 2006bFAO, 2007), and India (Mascarenhas & Jayakumar, 2008). examined the height at which P. odoratissimus and C. nucifera trees were broken in two tsunamis (the 2004 Indian Ocean and 2006 Java tsunamis) and found that the threshold of tsunami water depth at which a tree trunk broke was about 80% of the tree height for P. odoratissimus (Fig.10).…”

Section: (A) (B)mentioning

confidence: 99%

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Effectiveness and Limitations of Vegetation Bioshield in Coast for Tsunami Disaster Mitigagation

Tanaka¹

2011

The Tsunami Threat - Research and Technology

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Forest density is more effective than tree rigidity at reducing the onshore energy flux of tsunamis: Evidence from Large Eddy Simulations with Fluid-Structure Interactions

Mukherjee

Cajas²,

Houzeaux

et al. 2022

Preprint

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Communities around the world are increasingly interested in nature-based solutions to mitigation of coastal risks like coastal forests, but it remains unclear how much protective benefits vegetation provides, particularly in the limit of highly energetic flows after tsunami impact. The current study, using a three-dimensional incompressible computational fluid dynamics model with a fluid-structure interaction approach, aims to quantify how energy reflection and dissipation vary with different degrees of rigidity and vegetation density of a coastal forest. We represent tree trunks as cylinders and use the elastic modulus of hardwood trees such as pine or oak to characterize the rigidity of these cylinders. The numerical results show that energy reflection increases with rigidity only for a single cylinder. In the presence of multiple cylinders, the difference in energy reflection created by varying rigidity diminishes as the number of cylinders increases. Instead of rigidity, we find that the blockage area created by the presence of multiple tree trunks dominates energy reflection. As tree trunks are deformed by the hydrodynamic forces, they alter the flow field around them, causing turbulent kinetic energy generation in the wake region. As a consequence, trees dissipate flow energy, highlighting coastal forests reducing the onshore energy flux of tsunamis by means of both reflection and dissipation.

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Effects of Sand Dune and Vegetation in the Coastal Area of Sri Lanka at the Indian Ocean Tsunami

Cited by 17 publications

References 0 publications

Tsunami hazard assessment in the southern Colombian Pacific basin and a proposal to regenerate a previous barrier island as protection

Tsunami hazard assessment in the southern Colombian Pacific basin and a proposal to regenerate a previous barrier island as protection

Effectiveness and Limitations of Vegetation Bioshield in Coast for Tsunami Disaster Mitigagation

Forest density is more effective than tree rigidity at reducing the onshore energy flux of tsunamis: Evidence from Large Eddy Simulations with Fluid-Structure Interactions

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