The Effectiveness and Limit of Tsunami Control Forests

Shuto, Nobuo

doi:10.1080/05785634.1987.11924470

Cited by 120 publications

(70 citation statements)

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“…The DBH, one of the forest type parameters for numerical simulation, was examined against tree fragility under tsunami inundation. Shuto (1987) indicated the degree of damage to Pinus thunbergii using three categories: cut down, damage, and no damage. DBH of 0.1 m was indicated as a criterion of which trees will survive under an inundation of 4.65 m. Harada and Imamura (2005) applied a 0.15 m DBH for 3 m inundation depth with Pinus thunbergii to the numerical simulation, and Yanagisawa (2009) also applied the same criteria with Rhizophora.…”

Section: Inundation Simulation For Planned Plantationmentioning

confidence: 99%

“…Japanese black pine (Pinus thunbergii) and mangrove, for tsunami inundation were proposed based on the works of Shuto (1987) and Yanagisawa et al (2009). They found that the hydraulic drag of trees is significant when DBH (diameter at breast height) is more than 0.15 m, and the tsunami inundation depth does not exceed 4 m. When the inundation depth exceeds 4 m, there is a lesser chance for the forest to survive.…”

Section: Introductionmentioning

confidence: 99%

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Reduction of tsunami inundation by coastal forests in Yogyakarta, Indonesia: a numerical study

Ohira

Honda

Harada

2012

Nat. Hazards Earth Syst. Sci.

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Abstract. Coastal forests are known to protect coastal areas from environmental degradation. In this paper, we examined another important role of coastal forests -to mitigate tsunami devastations to coastal areas. Using a twodimensional numerical model (Harada and Imamura model, 2005), we evaluated the damping effects of a coastal forest to resist tsunami inundation in Yogyakarta, Indonesia. In the simulations, we set up a two-km long control forest with a representative topography of the study site and experimented its damping performance sensitivity under various width configurations, e.g. 20, 40, 60, 80, 100 and 200 m. The initial tsunami wave was set such that the inundation depth at the front edge of the forest would not exceed 4 m (tree fragility limit). The forest variables such as species, density, DBH, height and canopy size were determined from a typical forest of the site (Casuarina plantation, 4 trees/100 m 2 , Diameter at Breast Height = 0.20 m). The results showed that coastal forest with 100 m width reduced inundation flux, depth and area by 17.6, 7.0 and 5.7 %, respectively. Exponential models were found to describe the relationships between forest width and tsunami inundation transmission. An additional experiment was performed using actual topography and a forest plantation plan with 100 m width for 2.46 km 2 . In this experiment, the results showed that the plan would reduce inundation flux by 10.1 %, while the exponential model estimated it to be 10.6 %, close to the numerical model results. It suggests that statistical models of forest width and damping effects are useful tools for plantation planning, as it allows for quicker evaluation of the impact of coastal forest without simulation modeling that requires a lot of data, time and computing power.

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Section: Inundation Simulation For Planned Plantationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reduction of tsunami inundation by coastal forests in Yogyakarta, Indonesia: a numerical study

Ohira

Honda

Harada

2012

Nat. Hazards Earth Syst. Sci.

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“…Coastal ecosystems may indeed act as a buffer against tsunami through a reduction of water flow velocity and inundation depth, debris blockage, their life saving role for people washed away by waves, and formation of sand dunes resulting from sand accumulation in front of the forest (Shuto, 1987;Harada and Imamura, 2005). A number of publications and reports confirming the positive role of coastal vegetation in tsunami attenuation, and based predominantly on the qualitative evaluation of the pre-and post-tsunami situation in the affected areas, reached the public after the 2004 Indian Ocean tsunami event (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Shuto, 1987;Yanagisawa et al, 2009). The damage encompassed predominantly the first few tree rows facing an open sea, growing in estuaries or along channels as well as regions experiencing the maximum tsunami intensity.…”

Section: Introductionmentioning

confidence: 99%

Tsunami damping by mangrove forest: a laboratory study using parameterized trees

Strusińska-Correia¹,

Husrin

Oumeraci

2013

Nat. Hazards Earth Syst. Sci.

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Tsunami attenuation by coastal vegetation was examined under laboratory conditions for mature mangroves Rhizophora sp. The developed novel tree parameterization concept, accounting for both bio-mechanical and structural tree properties, allowed to substitute the complex tree structure by a simplified tree model of identical hydraulic resistance. The most representative parameterized mangrove model was selected among the tested models with different frontal area and root density, based on hydraulic test results. The selected parameterized tree models were arranged in a forest model of different width and further tested systematically under varying incident tsunami conditions (solitary waves and tsunami bores). The damping performance of the forest models under these two flow regimes was compared in terms of wave height and force envelopes, wave transmission coefficient as well as drag and inertia coefficients. Unlike the previous studies, the results indicate a significant contribution of the foreshore topography to solitary wave energy reduction through wave breaking in comparison to that attributed to the forest itself. A similar rate of tsunami transmission (ca. 20%) was achieved for both flow conditions (solitary waves and tsunami bores) and the widest forest (75 m in prototype) investigated. Drag coefficient CD attributed to the solitary waves tends to be constant (CD = 1.5) over the investigated range of the Reynolds number

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“…Once a tsunami wave train arrives inland, its energy is dissipated by gravitational forces and friction (17). The remaining wave energy determines the effects experienced inland-i.e., maximum flood distance, human casualties, and structural damage to buildings.…”

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confidence: 99%

Influence of coastal vegetation on the 2004 tsunami wave impact in west Aceh

Bayas

Marohn²,

Dercon³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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In a tsunami event human casualties and infrastructure damage are determined predominantly by seaquake intensity and offshore properties. On land, wave energy is attenuated by gravitation (elevation) and friction (land cover). Tree belts have been promoted as "bioshields" against wave impact. However, given the lack of quantitative evidence of their performance in such extreme events, tree belts have been criticized for creating a false sense of security. This study used 180 transects perpendicular to over 100 km on the west coast of Aceh, Indonesia to analyze the influence of coastal vegetation, particularly cultivated trees, on the impact of the 2004 tsunami. Satellite imagery; land cover maps; land use characteristics; stem diameter, height, and planting density; and a literature review were used to develop a land cover roughness coefficient accounting for the resistance offered by different land uses to the wave advance. Applying a spatial generalized linear mixed model, we found that while distance to coast was the dominant determinant of impact (casualties and infrastructure damage), the existing coastal vegetation in front of settlements also significantly reduced casualties by an average of 5%. In contrast, dense vegetation behind villages endangered human lives and increased structural damage. Debris carried by the backwash may have contributed to these dissimilar effects of land cover. For sustainable and effective coastal risk management, location of settlements is essential, while the protective potential of coastal vegetation, as determined by its spatial arrangement, should be regarded as an important livelihood provider rather than just as a bioshield. Indo-Australian and southeastern Eurasian tectonic plates 150 km off the coast of west Aceh, Indonesia, triggered one of the largest seismic events in the last four decades (1). The seaquake generated a tsunami with disastrous consequences in the region.Soon after the 2004 event, the possible effects of coastal vegetation regarding the impact caused by tsunamis (mitigating or aggravating) were researched into, especially under scenarios with initial water heights below 10 m (2-5). In Sri Lanka and India, coastal communities located behind tree cover were reported to be less affected than those directly exposed to the sea (2, 3, 6). Parameters such as stem diameter and height as well as a "bioshield" width were identified as key vegetation characteristics with a bearing on impact mitigation (6). However, several studies advocating bioshields have been criticized for lacking empirical evidence to support the protective function of vegetation, some even suggesting that bioshields may give a false sense of security to coastal populations (7-10). The role of vegetation in tsunami impact mitigation still remains a controversial issue (11-13). In the coastal regions of western Aceh in 2004, the potential for mitigating tsunami impacts appeared limited as a result of the massive energy released by waves with heights exceeding 20 m (13). Mangroves along this...

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The Effectiveness and Limit of Tsunami Control Forests

Cited by 120 publications

References 0 publications

Reduction of tsunami inundation by coastal forests in Yogyakarta, Indonesia: a numerical study

Reduction of tsunami inundation by coastal forests in Yogyakarta, Indonesia: a numerical study

Tsunami damping by mangrove forest: a laboratory study using parameterized trees

Influence of coastal vegetation on the 2004 tsunami wave impact in west Aceh

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