Wave-Driven Coastal Processes Through the Eyes of Three Phase-Resolving Models
Assaf Azouri1, Volker Roeber2, Martin D. Guiles1, Douglas S Luther3, Melissa Iwamoto4, Tara Owens5 and Janet M Becker6, (1)University of Hawaii at Manoa, Honolulu, HI, United States, (2)Université de Pau et des Pays de l’Adour, Anglet, France, (3)Univ Hawaii Manoa, Honolulu, HI, United States, (4)Pacific Islands Ocean Observing System, Honolulu, United States, (5)University of Hawaii Sea Grant, Wailuku, HI, United States, (6)Univ of Hawaii at Manoa, Honolulu, United States
Abstract:
Accurate wave runup and inundation forecasting is essential for coastal zone management, hazard prevention, and assessment of damage potential to coastal infrastructure. Observational and modeling work around Hawai’i have shown that the phenomena contributing to wave runup can be highly variable along any given coast, due to the variable geomorphology, suggesting that empirical formulations typically based on sparse observations will be inaccurate at most locations along a specific coast. Nearshore variability and the subsequent spatially-dependent runup are composed of wave-driven setup, and gravity (5 ~ 30 sec) and infragravity (0.5 ~ 30 min) motions, any one of which can be the largest contributor. Non-hydrostatic and Boussinesq types phase-resolving wave models, have the potential to provide accurate descriptions of the coastal wave processes contributing to wave-driven runup and inundation along complex coasts, and are already being implemented for inclusion in operational wave runup forecasts. However, it is crucial to understand the relative performance of these models, and that information is not available.
Wave simulations from three phase-resolving numerical models (BOSZ, XBeach and FUNWAVE) are compared to observational data in a harbor and along the exposed coast of northwest Oahu Is., Hawai’i, under highly energetic sea/swell forcing conditions. The characteristics of observed auto-spectra along the coast and inside the harbor are qualitatively reproduced by all three models. Inside the harbor, this agreement is particularly pronounced as all three models reproduce the observed resonant amplifications in several narrow frequency bands. Furthermore, a cross-spectral analysis reveals only small differences among the simulated wavenumber spectra along the coast. Inside the harbor, the wave field generated by the three models qualitatively replicates the observed harbor mode structure. The relative accuracies between the three models and the data will be discussed. All three models are suitable for replicating the observed characteristics in both frequency and wavenumber spectra.
