Why are tides especially large near Incheon on South Korea’s west coast?

The large tidal variations near Incheon on South Korea’s west coast are primarily caused by the combination of the shallow depth of the Yellow Sea and the region's complex, indented coastline.1

The Yellow Sea is a geologically unique, shallow portion of the continental shelf that significantly influences tidal behavior. In this area, the tidal system rotates in a counterclockwise direction, and the shallow waters, paired with the intricate, ria-style (creek-indented) coastline of the Korean peninsula, create some of the most pronounced tidal variations in the world. While tidal ranges along the Chinese coast are generally smaller, the shallower west coast of South Korea experiences high tidal ranges typically between 13 and 26 feet (4 to 8 metres), with maximum spring tide levels reaching nearly 30 feet (9 metres) at Incheon.21