Western Réunion

The western coast of Réunion — the leeward side, facing away from the dominant southeast trades — runs for around 40 km from the mouth of the Saint-Denis suburbs in the north to the reef's southern terminus near Saint-Leu. This coast holds the island's only significant fringing reef system, a near-continuous coral barrier 500 to 800 m offshore that creates a shallow lagoon between the reef crest and the beach. The lagoon is Réunion's primary zone for swimming, snorkelling, and beach recreation; it is also the most ecologically sensitive stretch of the island's coastline. The tidal regime on the western Réunion coast is semidiurnal with a modest spring range of 0.8 to 1.1 m — typical of islands in the central southwestern Indian Ocean, well away from the amplifying geometry of the Mozambique Channel. Two highs and two lows per day; the pattern is broadly regular through the neap-spring cycle. The small range has practical consequences for the lagoon: the inner reef flat and seagrass beds sit at depths of 0.5 to 2.0 m at mean water level, and a drop of even 0.5 m on a spring low can reduce already-shallow sections to bare rock or expose seagrass to air. Snorkellers need the incoming tide to cross the reef crest comfortably; anglers and paddlers in the lagoon adjust entry and exit to the tide state. Shark risk on the western coast is an independent consideration, managed through the Vigie-Requin programme — a monitoring system using underwater acoustic receivers and buoys to detect tagged sharks (primarily bull sharks and tiger sharks) near the coast. The programme issues daily beach-safety ratings for supervised sites; water entry is conditional on the rating, not the tide. The Vigie-Requin data and beach status are published online by the Groupement d'Intérêt Public Requin Réunion and are separate from tidal information. The Route du Littoral — the coastal motorway running north from Saint-Denis — passes through or above this coast on viaduct and tunnel, carrying around 100,000 vehicles per day and subject to periodic rockfall closure from the basalt cliffs above. The rebuilt section between Saint-Denis and the Roches Noires uses sea-supported viaducts to avoid the cliff face; the road's vulnerability to oceanic swell and rockfall makes it a notable engineering constraint on the island's transport infrastructure. SHOM (Service Hydrographique et Océanographique de la Marine), the French naval hydrographic service, is the authoritative source for Réunion tide tables. Predictions on TideTurtle come from Open-Meteo Marine, a gridded global ocean model; accuracy is typically within plus or minus 45 minutes on timing and 0.2 to 0.3 m on height above chart datum.