Hong Kong’s US$3.8 billion underground drainage network to prevent flooding

Hong Kong’s US$3.8 billion drainage network, basically a chain of underground tunnels that run the length of Hong Kong Island and has saved the city from floods.

Floods in Hong Kong are common and cost huge damage to life and property.

The tunnels would carry the water all the way to the sea. Two massive tunnel-boring machines were deployed for the construction in 2007. During construction vertical pits were dug to extract gravel and debris.

The drainage runs through the hills behind the city, tucked less than a dozen meters below the surface.

The city’s typhoon warning and protection systems, such as storm surge barriers divert large summer rains into storage tanks.

The deadliest typhoon hit the city in September 1906, killing an estimated 15,000 people, according to Hong Kong Observatory, 5% of the city’s then population of 320,000.

Hong Kong’s network of tanks and tunnels are believed to be a solution that acts on climate change. The city’s porous pavements, protected wetlands, rain gardens, and green rooftops, all of which can help absorb rainfall.