This study utilized a shock-capturing Boussinesq model FUNWAVE-TVD to investigate the maximum momentum flux in the solitary wave run-up zone over back-reef slopes. Validation results of the present model were compared to the previous version of FUNWAVE using the eddy viscosity breaking model to demonstrate the advantages of the shock-capturing method in predicting the breaking solitary wave transformation and run-up over fringing reefs. A series of numerical experiments was designed comprehensively and performed then to obtain a new formulation for the envelope of the spatial distribution of the maximum momentum flux within the solitary wave run-up zone over back-reef beaches, which is different from the one used over uniformly-sloping beaches. Finally, the effects of the variation of reef parameters (i.e., the fore-reef slope angle, reef flat width, and water depth over the reef flat) on the maximum momentum flux at the initial shoreline were investigated to better understand the role of fringing reefs in the mitigation of tsunami hazard.

The protective capability of fringing reefs against tsunami hazards has been reported in numerous post-disaster surveys. It is believed that global warming is changing the water level over the reef flat and reef surface roughness by sea-level rise and coral bleaching. For a better understanding of the influence of climate change on tsunami hazards over fringing reefs, this study utilized a shockcapturing Boussinesq wave model, FUNWAVE-TVD, to simulate the tsunami-like solitary wave propagation and run-up over fringing reefs. Calibrated and validated by the newly obtained experimental data, the present model with shock-capturing scheme, in which only the ratio of wave height to water depth is used to trigger wave breaking, shows reasonable prediction of solitary wave transformation and run-up height over sharply varying reef bathymetry. Numerical experiments were then carried out to investigate the effects of sea-level rise and degrading of the reef surface roughness on the solitary wave inundation distance and fluid force distribution in the inundation zone. Numerical results clearly demonstrate how tsunami hazards change within the inundation zone in response to higher water levels and lower reef roughness and suggest climate change, especially sea-level rise, will significantly increase tsunami hazards in the low-lying areas of the reef-lined coasts. Presented results are discussed for the effects of sea-level rise and coral bleaching on the solitary wave process and implications to further improve the resilience under the threat of climate change. ARTICLE HISTORY

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