Occitanie

The Occitanie coastline — Sète, Montpellier's beaches, Cap d'Agde, the Camargue fringes — faces the Mediterranean, and the Mediterranean is effectively non-tidal. Mean astronomical tidal range along this coast is under 0.3 metres. That is not a rounding error or a data gap; it is a fundamental characteristic of a semi-enclosed sea with a narrow connection to the Atlantic. What drives coastal water levels here has nothing to do with the moon's gravitational pull on ocean basins. Wind is the dominant force. The Marin — a warm, humid southerly wind — pushes water onshore, raising sea level by 0.3–0.5 m or more against the barrier beaches and into the lagoon systems. The Tramontane, a strong northerly, does the opposite: water is pushed offshore, exposing normally submerged sand. Barometric pressure adds another layer: a deep low-pressure system sitting over the Gulf of Lion can raise coastal water levels by 20–30 cm independently of wind. The coast is a classic barrier beach system. Étang de Thau behind Sète, Étang de Palavas behind Palavas-les-Flots, and a chain of similar lagoons (étangs) are separated from the open sea by narrow sand barriers. Tidal exchange through the grau — the narrow channels connecting étangs to the sea — is minimal. Water levels inside these lagoons respond primarily to wind-driven exchange and seasonal Mediterranean sea-level variation (the sea sits roughly 15–20 cm higher in autumn than in spring). Tide charts for this coastline still have value: they show the residual astronomical signal and help contextualise the baseline. But the operative question for anyone planning a beach day, a kite session, or a boat departure from Sète's fishing harbour is the wind forecast, not the tide table. Open-Meteo Marine provides the sea-level signal here; SHOM remains the authoritative French hydrographic source for all coastal safety decisions.