JapanThe MAOUDC project with huge underground water tanks is said to have helped Tokyo reduce 90% of infrastructure damage caused by floods in the area.
Minister of Natural Resources and Environment Tran Hong Ha on May 30 said that in order to cope with the recent frequent flooding, Hanoi city can in the short term use a drainage pump system, but in the long run it needs to be done. research technical solutions, such as build underground tanks large water storage like in Japan, both to hold water when it rains, and to have water for use in drought.
The huge underground project called the Metropolitan Area Underground Drainage Canal (MAOUDC) was put into operation in 2006 by Japan to protect the capital Tokyo and the surrounding area from the severe consequences of flooding.
Tokyo is the largest city in the world, with a long tradition of anti-flood due to its location on a plain surrounded by 5 river systems and 100 large and small rivers that continuously bulge through each season.
Rapid industrialization, urbanization, and uncontrolled groundwater extraction have caused some areas in Tokyo to sink below sea level.
Japan Self-Defense Forces soldiers evacuate people from a flooded area in Omuta city, Fukuoka prefecture, July 7, 2020. Image: Kyodo.
Although Japan has experienced centuries of flood protection, the current flood control system in Tokyo only really took shape after the war. In 1947, Hurricane Kathleen destroyed many infrastructures, killing thousands of city dwellers. A decade later, Typhoon Kanogawa continued to wreak havoc in Tokyo, flooding streets, homes and businesses.
Faced with the severe consequences of storms and floods, the Japanese government is determined to act. “During the post-war recovery period of the 1950s-1960s, the government still spent 6-7% of the national budget on disaster risk reduction efforts,” said Miki Inaoka, a disaster expert at the United States Cooperation Agency. Japan International Cooperation (JICA), said.
Tokyo planners must deal with a variety of “flood control problems,” ranging from heavy rains to tsunamis, or earthquakes that damage dykes or dam failures.
After decades of planning and construction of corresponding structures, Tokyo now has a flood control system with dozens of dams, reservoirs and dikes. The highlight of this system is the labyrinth of underground Tokyo tunnels, which form alongside subway lines and gas pipelines.
The Tokyo government has built 10 underground lakes and 3 anti-flood tunnels. Currently, Tokyo is continuing to build more anti-flood systems to cope with the increasing rainfall caused by climate change.
Within this system, the MAOUDC is the world’s largest flood defense structure, which is said to be an underground shield that protects Tokyo from flooding. Construction began in 1992 and was completed after 13 years of construction, with a total cost of 230 billion yen (2.2 billion USD).
Diagram of the Metropolitan Area Underground Drainage Channel (MAOUDC) in Tokyo, Japan. Graphics: New Economy.
This underground system draws water from small and medium rivers in the northern Tokyo area, pouring it into five giant underground tanks, each 70 meters high, large enough to hold a space shuttle or the Statue of Liberty. do. The water in the underground tank will then be circulated through a 6.3 km long tunnel and discharged by 78 large-capacity pumps into the Edo River at a speed of nearly 200 cubic meters per second.
If the water in the Edo River rises, MAOUDC will reduce the flow through a giant pressure control tank the size of two football fields, so that the pumps can regulate and push the water into the river.
This vital control tank was called the “Pantheon” (Temple) due to its 59 large pillars supporting it, making it look like a shrine to a Greek god.
The MAOUDC underground tank system helps Tokyo cope with floods. Video: Earth Titan.
MAOUDC operates about 7 times a year, especially during the typhoon season from June to the end of October in Japan. “In this area, heavy rains, storms, or even daily rainfall can cause flooding,” said Nobuyuki Akiyama, MAOUDC control tank manager. “This system has helped prevent 90% of infrastructure damage due to flooding in the area.”
“It’s like a base from a science fiction story,” said Miki Inaoka, a disaster expert at JICA. MAOUDC will be open to visitors when it is not in operation, in an effort to increase public awareness of the importance of disaster management.
However, Inaoka concedes climate change will challenge Tokyo’s flood-resistant infrastructure, as extreme weather becomes more frequent and unpredictable, making flood planning difficult. .
“The nature of Japan’s climate makes the country often suffer from floods and heavy rains,” said Kei Yoshimura, a professor of meteorology at the University of Tokyo.
Based on historical rainfall data, the city government designed Tokyo’s defenses to withstand 50 mm of rain per hour. However, some experts estimate that in the 21st century, Japan’s rainfall could increase by 10% and up to 19% in the summer.
Employees at the control tank “Temple” of the MAOUDC flood control system in Kasukabe, north of Tokyo, September 3, 2020. Image: AFP.
In a book published in 2014, Nobukuyi Tsuchiya, director of the Japan Rivers Research Center, warned Tokyo was not ready to deal with heavy rains caused by global warming. In low-lying areas like Tokyo, around 2.5 million people could be affected by flooding in the event of a record high tide.
In early 2018, heavy rains in western Japan killed hundreds of people and caused millions of dollars in economic damage, when many rivers burst their banks, causing severe flooding. If such a situation happened to Tokyo, the city would be severely affected even with the current flood control system, Tsuchiya said.
“If a country as well-prepared as Japan is affected, if a city like Tokyo is to flood, we should all be on our guard,” said Cecilia Tortajada, water management expert at the Water Policy Institute. of the Lee Kuan Yew School of Public Policy, Singapore.
Duc Trung (Follow BBC, AFP)
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