Numerical investigation on tsunami wave mitigation on forest sloping beach
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Numerical investigation on tsunami wave mitigation on forest sloping beach Mingliang Zhang1*, Yongpeng Ji1, Yini Wang1, Hongxing Zhang1, Tianping Xu1 1 School of Ocean Science and Environment, Dalian Ocean University, Dalian 116023, China
Received 29 January 2019; accepted 11 March 2019 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract
An explicit one-dimensional model based on the shallow water equations (SWEs) was established in this work to simulate tsunami wave propagation on a vegetated beach. This model adopted the finite-volume method (FVM) for maintaining the mass balance of these equations. The resistance force caused by vegetation was taken into account as a source term in the momentum equation. The Harten–Lax–van Leer (HLL) approximate Riemann solver was applied to evaluate the interface fluxes for tracing the wet/dry transition boundary. This proposed model was used to simulate solitary wave run-up and long-periodic wave propagation on a sloping beach. The calibration process suitably compared the calculated results with the measured data. The tsunami waves were also simulated to discuss the water depth, tsunami force, as well as the current speed in absence of and in presence of forest domain. The results indicated that forest growth at the beach reduced wave energy loss caused by tsunamis. A series of sensitivity analyses were conducted with respect to variable parameters (such as vegetation densities, wave heights, wave periods, bed resistance, and beach slopes) to identify important influences on mitigating tsunami damage on coastal forest beach. Key words: shallow water equations, HLL scheme, tsunami waves, coastal vegetation, wave propagation Citation: Zhang Mingliang, Ji Yongpeng, Wang Yini, Zhang Hongxing, Xu Tianping. 2020. Numerical investigation on tsunami wave mitigation on forest sloping beach. Acta Oceanologica Sinica, 39(1): 130–140, doi: 10.1007/s13131-019-1527-y
1 Introduction Tsunamis are giant waves in the ocean, which are generally generated by marine earthquakes, underwater volcanic eruptions, or submerged landslides in the deep sea. They propagate from the deep sea to the coastline with vast losses to life and property, destruction of critical infrastructure in low-lying coastal areas, and massive damage to the coastal ecosystem (such as the Indian Ocean tsunami in 2004, Samoa tsunami in 2009, Chile tsunami in 2010, and Tohoku tsunami in 2011) (Ulvrová et al., 2014). These great threats of tsunami waves in coastal regions demonstrate the necessity of building artificial obstacles to mitigate the hazardous effects caused by tsunamis. The shallow water equations(SWEs) can usually be used to describe wave propagation in the ocean; the need in wavelength of water wave is much longer than the water depth (Wu et al., 2016). Vreugdenhil (1994) concluded that the SWEs provided a roughly reasonable model in simulating tsunami propagation. With advances in numerical simulation technology and methodology, several types of numerical m
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