Why Are Japanese Cities Rarely Flooded

In recent days, many places in China have experienced heavy rainfall, and heavy rainfall has caused the depth of the area to be seen everywhere. According to this phenomenon, Xiao Bian specially searched for a very good Tokyo, Japan, how to prevent it?

Developed countries represented by Japan have the most advanced drainage system in the world. Among them, an environmentally-friendly sewer drainage system constructed in Japan, in addition to being used for various sewage purification treatments, is also used to deal with storm drainage during the typhoon period. Therefore, Japanese cities are almost never flooded.

Drainage system deep underground 60 meters


The underground drainage system in the Tokyo area was mainly built to avoid the typhoon and rain disasters. This system is called "the world's most advanced sewer drainage system", and its drainage standard is "one to five years" (the fact is reached in China's once-in-a-century). It consists of a series of concrete pits with a depth of 50 meters.

The underground drainage pipe is basically based on the “confluent pipe system” (sewage and rainwater are discharged by the same pipe). The total length of sewage pipes, rainwater pipes and confluence pipes in Tokyo exceeds 15,000 km.

The drainage system outside the Capital Circle consists of a series of concrete pits. Each concrete pit is 65 meters high (about 22 floors) and 32 meters wide. It is formed by connecting 6.3 kilometers of tunnels at a depth of 50 meters underground.


In addition, there is a giant pressure tank: 25.4 meters high (about eight floors), 177 meters long, 78 meters wide. The interior of the underground waterway in Tokyo is like a city, driving freely in and out.

The sewer reflects Japan’s “details”


The drainage system in Tokyo also reflects the meticulous pursuit of Japanese people.

In order to ensure the smoothness of the drainage channel, the Tokyo Sewerage Bureau, which is responsible for the main duties, began to intervene from the stage of sewage discharge.


First of all, they stipulate that some insoluble toilet wastes are not allowed to be discharged directly into the sewers, but must be sorted by the waste sorting system.

The oil produced by cooking is also not allowed to be directly introduced into the sewer, because it will corrode the drainage pipe in addition to the stench of the adjacent sewer.

The Tokyo Sewerage Bureau’s approach to this is to wipe the oil off with a newspaper and treat the oily newspaper as combustible garbage. The Sewerage Bureau even has a webpage and classroom dedicated to healthy cooking, introducing less oily and healthy recipes.

For example, the drainage pipes of each building are not one pipe to the bottom. Many houses have some water storage buckets. If there are more water storage buckets, the overall drainage pressure will be faced when sudden precipitation occurs. It will be much lower.