Incheon tide times

Incheon sits on the western coast of Korea where the Han River estuary meets the Yellow Sea — called the West Sea in Korean, Hwanghae in Chinese. This is a coast of extreme tides. Spring tidal range at Incheon reaches 8 to 9 m, placing it unambiguously among the world's largest semidiurnal tide ranges. For context: Mont Saint-Michel in Brittany, perhaps the most famous tidal landmark in Western Europe, has spring ranges of 6 to 8 m. The Bay of Fundy on the Canada-US border holds the global record at 14 to 16 m. Incheon sits between those two benchmarks — dramatically larger than anything on the European Atlantic coast, and approaching, though not matching, the Fundy extreme. It is not a moderate or even a large tide. It is one of the most extreme tidal environments on Earth.

The physical reason is the geometry and bathymetry of the Yellow Sea. It is a shallow, semi-enclosed basin — average depth around 44 m, connected to the open Pacific only through the narrow Korea Strait in the south and the Bohai Strait in the north. A large tidal volume enters and exits through those restricted openings, and the resonant period of the basin closely matches the semidiurnal tidal forcing period of roughly 12 hours and 25 minutes. That near-resonance is the amplification mechanism, the same physics that produces the Fundy tides at their extreme. The Korean coast at Incheon is at the eastern end of the Yellow Sea where the amplification peaks.

The practical consequences of an 8 to 9 m spring range are not subtle. At low water on a spring tide, the sea surface at Incheon drops to roughly 4 to 4.5 m below its high-water position. The tidal flats — called getbol in Korean — extend kilometres from the pre-reclamation shoreline and represent one of the world's most productive intertidal ecosystems: shellfish, wading birds including the critically endangered spoon-billed sandpiper, and the mudskipper fish that have adapted to a life that is half-marine, half-terrestrial. The Gyeonggi tidal flats, the broader system of which Incheon's coast is the most urbanised part, are inscribed on the UNESCO World Heritage List as part of the Korean Getbol inscription.

Reclamation has transformed this coastline over the past 40 years. Songdo International Business District — roughly 600 hectares of reclaimed land built into the Yellow Sea south of Incheon's inner harbour, linked to the mainland by causeway — is perhaps the world's largest purpose-built new city on former tidal flat. The land was below sea level before reclamation and is protected by sea walls engineered against storm surge on a coast where surge can add several metres above an already extreme astronomical high. The district is built around a central park canal and faces Central Park's waterway; none of the original tidal flat character remains in the reclaimed zone, though the unreclaimed mudflats visible from Songdo's western edges at low tide show what the pre-reclamation coast looked like for kilometres.

Wolmido Island, now a peninsula connected to the main city by a kilometre-long causeway built across the tidal flat in the 1970s, holds the Wolmido Theme Park and a dense row of seafood restaurants along the harbour-facing street. The harbour at Wolmido is a working fishing harbour where the extreme tide range has direct consequences: at low water, many of the berths are resting on the soft mudflat or in very shallow water, and the vessels sit on the bottom. Tidal gates and floating pontoon berths are used for the larger charter fleet; smaller traditional boats simply dry out at low tide, as they have done here for centuries.

Incheon International Airport occupies Yeongjong Island, connected to Incheon city and the mainland by the Incheon Grand Bridge and the Airport Expressway, both spanning tidal channels that expose the mudflat on a large spring ebb. The airport's construction and the bridge foundations required detailed analysis of the tidal and current regime in those channels. The extreme tidal range at Incheon means that storm surge risk is evaluated at a different scale than on moderate-range coasts — a 1 m surge on top of a 9 m spring high produces a water level that the seawall and reclamation embankments are engineered to contain.

The Korea Hydrographic and Oceanographic Agency (KHOA) maintains the principal Incheon tide gauge and publishes harmonic predictions for Korean ports. The Incheon gauge record is one of the longest continuous sea-level records in Northeast Asia, and its data underpin the Yellow Sea tide models used in regional research. Predictions on this page come from Open-Meteo Marine, a gridded global ocean model — typically within plus or minus 45 minutes on timing and 0.2 to 0.3 m on height. On a coast with an 8 to 9 m spring range, those errors are a small fraction of the total signal. For the precise minutes of high and low at Incheon, KHOA's published harmonic predictions apply.