Abstract
Abstract. 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.
Highlights
OefcothsyestceomasstaDml afyoynreiasntdmseesiducbsajecctt to as extreme a buffer model was selected among the tested models with different against tsunami through a reduction of water flow velocity frontal area and root density, based on hydraulic test results
The results indicate a significant contribution of the foreshore topography to solitary wave energy reduction through wave breaking in comparison to Indian Ocean tsunami evGente(oe.sg.cDieahndtoiufihc-Guebas et al, 2n0u0m5b;eUr NofEcPasRueMapltoioertsd, a2es0l0w5De;llEeaJvsFmeRilenopiompratm,l2de0a0mn6a)t.gTe hseufvfeerryedlobwy that attributed to the forest itself
The reliability of the performance of coastal forest damping obtained from hydraulic scale modelling is very much dependent on the parameterization method applied to the tree models constituting the forest
Summary
A simplification of the very complex three-dimensional tree structure with randomly distributed roots and branches was necessary for consistent modelling. A much higher rate of flow attenuation is expected in the case of a complex and denser root system, such as prop roots typical for red mangroves (Rhizophora sp.), than for other mangrove species (Fig. 1a). The relationship between submerged root volume ratio and water depth, obtained by Mazda et al (1997) for different mangrove species in Japan and Australia, was used as a reference to determine the root density of the prototype tree (termed hereafter “real mangrove model”). Three real mangrove models of different root density were constructed to investigate the influence of the submerged root volume ratio on the hydraulic resistance of the models: model A1 with low root density, model B1 with medium root density and model C1 with high root density (Fig. 2). More details of the tree parameterization method can be found in Husrin et al (2012) and Husrin (2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
