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Open AccessArticle

Numerical Investigations of Tsunami Run-Up and Flow Structure on Coastal Vegetated Beaches

1
School of Ocean Science and Environment, Dalian Ocean University, Dalian 116023, China
2
State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116023, China
*
Author to whom correspondence should be addressed.
Water 2018, 10(12), 1776; https://doi.org/10.3390/w10121776
Received: 23 October 2018 / Revised: 28 November 2018 / Accepted: 29 November 2018 / Published: 3 December 2018
(This article belongs to the Special Issue Ocean Exchange and Circulation)
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Abstract

Tsunami waves become hazardous when they reach the coast. In South and Southeast Asian countries, coastal forest is widely utilized as a natural approach to mitigate tsunami damage. In this study, a depth-integrated numerical model was established to simulate wave propagation in a coastal region with and without forest cover. This numerical model was based on a finite volume Roe-type scheme, and was developed to solve the governing equations with the option of treating either a wet or dry wave front boundary. The governing equations were modified by adding a drag force term caused by vegetation. First, the model was validated for the case of solitary wave (breaking and non-breaking) run-up and run-down on a sloping beach, and long periodic wave propagation was investigated on a partially vegetated beach. The simulated results agree well with the measured data. Further, tsunami wave propagation on an actual-scale slope covered by coastal forest Pandanus odoratissimus (P. odoratissimus) and Casuarina equisetifolia (C. equisetifolia) was simulated to elucidate the influence of vegetation on tsunami mitigation with a different forest open gap. The numerical results revealed that coastal vegetation on sloping beach has significant potential to mitigate the impacts from tsunami waves by acting as a buffer zone. Coastal vegetation with open gaps causes the peak flow velocity at the exit of the gap to increase, and reduces the peak flow velocity behind the forest. Compared to a forest with open gaps in a linear arrangement, specific arrangements of gaps in the forest can increase the energy attenuation from tsunami wave. The results also showed that different cost-effective natural strategies in varying forest parameters including vegetation collocations, densities, and growth stages had significant impacts in reducing the severity of tsunami damage. View Full-Text
Keywords: tsunami waves; numerical simulation; wave run-up; flow structure; coastal vegetation tsunami waves; numerical simulation; wave run-up; flow structure; coastal vegetation
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Zhang, H.; Zhang, M.; Xu, T.; Tang, J. Numerical Investigations of Tsunami Run-Up and Flow Structure on Coastal Vegetated Beaches. Water 2018, 10, 1776.

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