Tokyo's G-Cans underground flood channel (1992-2006)
After typhoon floods repeatedly swamped homes in Saitama Prefecture, Japan built the Metropolitan Area Outer Underground Discharge Channel, a 6.3km system of tunnels and five shafts up to 70 metres underground that diverts floodwater into the Edo River.
The system cut flooding in several Tokyo-area basins, though extreme rains still overwhelm it occasionally.
It became a reference case for cities choosing large engineered flood fixes over piecemeal repairs.
Like Tasreef, it is a single giant infrastructure answer to a recurring flooding problem, built on a multi-decade horizon.
