`Tokyo's $1.6 Billion Flood Cathedral Worked Perfectly. 4,000 Homes Flooded Anyway.

Under a playing field north of Tokyo there is a concrete hall held up by 59 pillars, each as tall as a 6-story building. It is the end of a $1.6 billion system built to move floodwater out of small rivers and into a bigger one. On June 2, 2023, it did exactly what it was designed to do. By morning, water stood in roughly 4,000 homes. Nothing broke that night. So how does a flood defense do everything right and still lose? The answer is in the numbers chosen in the early 1990s, and in what the rain has done since. Chapters: 0:00 The room under the field 1:25 A plain as flat as a tray 2:34 Five shafts, one tunnel, 59 pillars 4:09 The test: 154 activations 4:54 Three limits nobody sees 6:11 June 2, 2023: what really happened 7:11 A typhoon 600 km away 7:30 What Japan is building now 8:23 The ring on the pillars The reconstructions and visuals in this video are AI-generated illustrations. Figures come from Japan's land ministry, Saitama Prefecture and news reports; the full source list is in the pinned comment. #Tokyo #Engineering #Megaprojects tokyo underground cathedral, g-cans, tokyo flood tunnel, metropolitan area outer underground discharge channel, kasukabe, japan flood control, tokyo flood defense, japan megaprojects, engineering documentary, underground discharge channel, typhoon hagibis, typhoon shanshan, koshigaya flood 2023, edo river, saitama, how japan stops floods, climate change infrastructure, extreme rainfall, megastructures, load limit Sources: Reuters, October 2024 (Tokyo expands underground "cathedral" complex): https://japantoday.com/category/national/t... Japan MLIT, Edogawa River Office (pumps and discharge): https://www.ktr.mlit.go.jp/edogawa/edogawa... Japan MLIT, flood history of the basin: https://www.ktr.mlit.go.jp/ktr_content/con... Saitama Shimbun, June 5, 2023 (flooded homes): https://www.saitama-np.co.jp/articles/2999... Straight Arrow News: https://san.com/cc/tokyo-to-expand-undergr...