Incheon Airport's land holds four islands because the tidal flats between them were closed off with 17.3 kilometers of seawall and filled in

How we checked

Checked on October 3, 2026. We compared the video against the originals of Incheon International Airport Corporation's website page "Phase 1 Construction Projects" (1단계 건설사업) and its post "Site Preparation Work" (부지조성 공사) (December 31, 2019), the National Archives of Korea's "Record of the Month, March 2010" (이달의 기록 2010년 3월), and a Ministry of Oceans and Fisheries announcement (Korea Policy Briefing, September 23, 2015). The names of the islands at the ends of the north and south seawalls (sentences 9 and 10), the 10-meter gap left after building from both ends, the October 29, 1994, closure and the trucks every 50 seconds (sentences 11, 12, 20 and 21) were confirmed through the Hankook Ilbo report of November 1, 1994, which carried the New Metropolitan Airport Construction Corporation's explanation; the 1-meter depth at high tide (sentence 6), the 82% of the land that was sea (sentence 17), the fill cut from hills (sentence 24), and Sammok Ferry Terminal and Sinbul IC (sentences 27 and 28) were confirmed through the 2020 Kyeongin Ilbo series and a 2018 Kiho Ilbo article, so these are marked as reported (△). "Seawater flowing in and out twice a day," "as long as the gap is open, the area inside the seawalls is sea," "the four islands as posts to anchor the seawalls" and "the area inside the seawalls is land to be filled" are not figures from the originals but our explanation linking the seawall endpoints and the order of the closure, so they are marked as interpretation.

• Seawall lengths are given as 7.3 north, 6 south, 4 east and 17.3 kilometers in total by Incheon International Airport Corporation; as 7.31 north, 6.08 south and 17 kilometers in total by the 1994 Hankook Ilbo report; and as 3.9 kilometers east by the 2018 Kiho Ilbo report. The video used the corporation's figures.
• The endpoints of the north seawall (Sammokdo–Yongyudo) and south seawall (Sinbuldo–Yongyudo) were confirmed through the 1994 report, but we found no original saying where the east seawall runs from and to, so the video says only "4 kilometers on the east." "The four islands as posts that anchored the seawalls" is an interpretation linking these endpoints with the report's "closing off between Yeongjongdo and Yongyudo."
• The 9.9-meter tidal range is the maximum the Ministry of Oceans and Fisheries predicted around Chuseok 2015 based on observations at Incheon, not a value at the airport site. Saying seawater flows in and out "twice a day" is a general description of the tides that we did not confirm against a sentence in an original.
• The 82% of the land that was sea agrees across two reports, Kyeongin Ilbo (46 million ÷ 56,198,600 square meters) and Kiho Ilbo (46,281,000 square meters of tidal flat ÷ about 56.2 million square meters in total, about 82.4%), but we found no corporation or government original.
• The 5-meter thickness of the fill, the soil from cut-down hills and the soil taken from the sea were confirmed only through reports. "Sea sand" is a shortened form of the report's "soil taken from the nearby sea."
• The final closure date of October 29, 1994, appears only in reports from the time; Korean Wikipedia gives October 30 without a source.
• We do not include people's names or street addresses.