Articles | Volume 13, issue 2
Nat. Hazards Earth Syst. Sci., 13, 483–503, 2013
https://doi.org/10.5194/nhess-13-483-2013

Special issue: Tsunami impacts on- and offshore in the Andaman Sea region

Nat. Hazards Earth Syst. Sci., 13, 483–503, 2013
https://doi.org/10.5194/nhess-13-483-2013

Research article 25 Feb 2013

Research article | 25 Feb 2013

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

A. Strusińska-Correia1, S. Husrin*,1, and H. Oumeraci1 A. Strusińska-Correia et al.
  • 1Leichtweiß-Institute for Hydraulic Engineering and Water Resources (LWI), Department of Hydromechanics and Coastal Engineering, Technische Universität Braunschweig, Germany
  • *now at: Research Institute of Coastal Resources and Vulnerability, Ministry of Marine and Fisheries Affairs, Republic of Indonesia

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.

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