Wave-tide interaction and implications for flooding
It is the combination of mean sea-level, tides, storm surges and wave processes, which drives coastal flooding. Therefore, the interaction of these physical processes is essential in coastal flood risk understanding. Tide-wave interaction is a well-known processes that can influence the wave generation or propagation; for example, tidal currents alter atmosphere-ocean energy transfer and can refract waves into a region. We hypothesize wave-tide interaction is an important effect in coastal flood risk for regions of strong tidal dynamics, such as the UK, an use a dynamically coupled wave-tide model to explore this process. For example, if wave-tide interaction results in larger waves at high tide, and this process changes in the future, then the hazard to coastal flooding may increase.
The COAWST model, which dynamically couples the 3D hydrodynamics (ROMS) and wave (SWAN) models, is applied to the Irish Sea (UK) – a region of large tides. A two month period was simulated (Jan-Feb 2014) and validated well. The influence of tides on the modulation of wave height was calculated. Fine-scale variability in the tidal effect to wave height at high water were found, with some regions experiencing a 20% increase in wave height at high tide. Model sensitivity to spatial resolution and sea-level rise was investigated, and found to influence simulated wave-tide interaction because tidal current speeds are altered.