BinWaves: An additive hybrid method to downscale directional wave spectra to nearshore areas

Accurate and timely early warning systems are a vital component in mitigating the risks faced by coastal communities worldwide. Unlike aggregated wave parameters, information extracted from the complete directional wave spectra is often indispensable in the development of such systems in multi-modal environments, such as remote islands, where concurrent waves from various directions are common. Dynamically simulating the wave propagation, although accurate, can be computationally demanding and time-consuming, particularly for resource-constrained communities. In this study, we introduce as an alternative, a novel additive hybrid model known as BinWaves. This model relies on the propagation of a reduced number of monochromatic wave systems and linear wave theory, facilitating the efficient reconstruction of the full directional wave spectra in nearshore areas. To showcase the capabilities of BinWaves, we have implemented the system in the Pacific Islands of Samoa and American Samoa and validated it against full spectral numerical simulations and available buoy data. Given its similar accuracy and higher computational efficiency when compared with dynamic wave models, BinWaves has proven to be a great alternative for reconstructing historical time series, or, more importantly analysing climate change scenarios, tasks that go beyond the capacities of small islands developing states.