Tsunami attenuation by coastal vegetation was examined under laboratory conditions for mature mangroves <i>Rhizophora</i> 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 <i>C</i><sub>D</sub> attributed to the solitary waves tends to be constant (<i>C</i><sub>D</sub> = 1.5) over the investigated range of the Reynolds number
The systematic laboratory investigation on tsunami attenuation by flexible mangrove models was performed in order to improve the knowledge on tsunami-coastal forest interaction. A sophisticated parameterization method, based on structural and bio-mechanical properties of a mature mangrove (Rhizophora sp.), was developed for the construction of the mangrove models under assumption of stiff and flexible structure. The forest model examined in the laboratory experiments consisted of the selected flexible mangrove models, arranged in different configurations, which was impacted by a tsunami-like solitary wave of varying height, propagating in different water depths. Based on the envelopes of max. wave height and wave forces induced on single tree models, wave evolution modes were determined to identify the source of wave attenuation. The results indicate the dependence of wave transmission on the observed wave evolution modes and relative forest width: the highest transmission coefficient is attributed to nonbreaking waves (ca. 0.78 and 0.55 for forest width of 0.75 and 3.0 m, respectively), while the lowest transmission coefficient corresponds to wave breaking in front of/in the forest model (ca. 0.5 and 0.3 for forest width of 0.75 and 3.0 m, respectively).
A study on the nonlinear transformation of a tsunami-like solitary wave over impermeable submerged structures of finite widths was performed to examine the feasibility of the integration of such structures into tsunami coastal protection systems. Laboratory experiments with varying structure geometry and incident wave conditions were conducted to determine wave evolution modes, incipient wave breaking and the number of solitons resulting from the wave fission process. The latter was found to be constant for a given relative structure submergence depth and width, irrespective of incident wave conditions, and tended to increase for smaller freeboards and larger barrier widths. The hydraulic performance of the structure, predicted numerically for more realistic tsunami conditions by means of the Boussinesq-type model COULWAVE, was determined in terms of wave transmission, wave reflection and wave energy dissipation coefficients. The rate of wave transmission and energy dissipation was dependent on the breaking conditions over the structure crest: the weakest wave attenuation (approximately 10%) corresponded to nonbreaking waves, while the highest wave damping (about 25%) was achieved for the widest relative structure width (B/Li = 1.0) and the smallest relative structure submergence depth (dr/h = 0.3) investigated.
The 2011 Tōhoku event showed the massive destruction potential of tsunamis. The EuroJapan "Risk assessment and design of prevention structures for enhanced tsunami disaster resilience (RAPSODI)" project aimed at using data from the event to evaluate tsunami mitigation strategies and to validate a framework for a quantitative tsunami mortality risk analysis. Coastal structures and mitigation strategies against tsunamis in Europe and Japan are compared. Failure mechanisms of coastal protection structures exposed to tsunamis are discussed based on field data. Knowledge gaps on failure modes of different structures under different tsunami loading conditions are identified. Results of the wave-flume laboratory experiments on rubble mound breakwaters are used to assess their resilience against tsunami impact. For the risk analysis, high-resolution digital elevation data are applied for the inundation modeling. The hazard is represented by the maximum flow depth, the exposure is described by the location of the population, and the mortality is a function of flow depth and building vulnerability. A thorough search for appropriate data on the 2011 Tōhoku tsunami was performed. The results of the 2011 Tōhoku tsunami mortality hindcast for the city of Ishinomaki substantiate that the tsunami mortality risk model can help to identify high-mortality risk areas and the main risk drivers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.