Gazi, M. Y., da Silva, A. P., Villacieros-Robineau, N., Fellowes, T. E., Salles, T., Alejo Flores, I., González-Villanueva, R., & Vila-Concejo, A. (2026). Spatial variability of wave signatures and profile morphotypes of beaches in estuaries and bays across different tidal regimes. Geomorphology. https://doi.org/10.1016/j.geomorph.2026.110208

The second chapter of my PhD thesis has now been published! Beaches in Estuaries and Bays (BEBs) are often assumed to be low-energy environments shaped mostly by local winds because they are “sheltered” from the open ocean. But when we measured what waves actually reach these beaches in Pittwater (Sydney, Australia) and the Ría de Vigo (Galicia, Spain), the story changed completely. Using in-situ pressure sensors, long-term beach surveys, and sediment analysis, we separated waves into: Ocean swell waves, locally generated wind waves, and Infragravity waves.

What we found:

• In microtidal Pittwater, ~52% of wave energy came from ocean swell
• In mesotidal Ría de Vigo, ~90% of wave energy came from ocean swell
• Beaches closer to the estuary entrance receive more swell energy. Beaches further inside receive much less.

This creates a clear pattern within the same estuary:

Near entrance	Mid-estuary	Inner estuary
High swell energy	Mixed wave energy	Very low swell
Convex profiles	Transitional	Concave profiles
Coarser, well-sorted sediments	Mixed sediments	Fine, poorly sorted sediments

More swell exposure → Convex (steeper, accretional) beach profiles
Less swell exposure → Concave (flatter, erosive) beach profiles

Why tidal regime still matters

Although swell is the main driver, tidal range modifies how waves interact with the beach:

• In Pittwater (microtidal), infragravity and wind waves play a bigger secondary role
• In Ría de Vigo (mesotidal), swell dominance is even stronger, but tides influence sediment mobility and profile adjustment