Tokyo averts floods with an intricate cavern of underground tunnels and vaults
Jun 12, 2023
About 14 storeys beneath bustling Tokyo, or 42m underground, lies a cavern of tunnels and vaults that temporarily stores swelling rainwater to prevent flooding above ground.
Climate change has, however, drastically increased the risks of inundation, given higher odds of stronger typhoons and prolonged bouts of heavy rainfall.
Plans are under way to further grow the city’s operational reservoir capacity to 3.6 million cubic metres – from the current 2.64 million cubic metres – by the end of this decade, with the construction of more underground facilities, officials from the Tokyo Metropolitan Government (TMG) told The Straits Times on Friday.
On top of that, another 1.5 million cubic metres of reservoir storage is expected to be under construction in 2030, with Tokyo aiming for a total planned capacity of 5.1 million cubic metres, which is enough for 2,040 Olympic-size pools. ST understands that this number will be reviewed again in fiscal 2023, which begins on Saturday. This is part of a 6.6 trillion yen (S$66 billion) plan to strengthen the capital’s resilience against flooding, alongside plans to raise coastal sea walls and river embankments. The current system of 28 so-called “regulating reservoirs”, with a capacity enough for 1,056 Olympic-size pools, comprises 16 in-ground reservoirs, nine underground vaults, and three underground tunnels.
But Tokyo’s urban planners are increasingly concerned that this existing network is not robust enough to cope with extreme weather events. Mr Tetsuro Fujisaki, TMG’s director for urban resilience, told ST that Tokyo had a close shave when Typhoon Hagibis slammed directly into the capital in October 2019, bringing a record-breaking total precipitation of 650mm. While the network of underground vaults and tunnels kept flooding to within 0.85 sq km – with damage to about 600 buildings – it was brought nearly to the brink: One vault was 98 per cent full, while another tunnel, 91 per cent.
“Typhoons and torrential downpours are expected to become increasingly frequent and severe due to climate change,” Mr Fujisaki said, citing the United Nations’ Intergovernmental Panel on Climate Change forecasts of a rise in temperatures by 2 deg C by 2100. TMG’s forecasts show that this will bring 1.1 times more rainfall and a 60cm increase in sea levels to the capital.
Tokyo is sharing its expertise of using underground space to manage flooding risks with regional capitals such as Kuala Lumpur and Jakarta. ST also reported in January that Singapore’s national water agency PUB is exploring the use of underground space to combat inland and coastal flooding. The buttressing of anti-flooding measures is one of five pillars under the Tokyo Resilience Project announced by the city’s Governor Yuriko Koike in December 2022, ahead of the centennial of the Great Kanto Earthquake on Sept 1, 1923, that flattened Tokyo and killed more than 100,000 people.
The other four pillars of the project, with an overall budget of 15 trillion yen and expected to run into the 2040s, include measures against earthquakes, volcanic eruptions, power and communication disruptions, and infectious diseases.
On a recent visit to the Kanda River/Ring Road No. 7 underground regulating reservoir, Mr Kimihito Mukoyama of the TMG’s Bureau of Construction told ST that the facility has taken in water 44 times since it became operational in 1997. He compared two typhoons – one in August 1993 and another in October 2004 – to show its impact. While the 1993 typhoon brought 288mm of rainfall and flooding to an area of 85ha, flooding from the 2004 typhoon was capped at 4ha despite similar precipitation of 284mm.
ST understands that despite measures to reduce flooding damage, TMG officials believe it is next to impossible to eradicate flooding completely during heavy downpours given the capital’s concrete terrain, as some inland areas are far from river drainage systems. And while in-ground reservoirs are easier and faster to build, Tokyo dug deep underground – the vaults and tunnels run even deeper than its subway lines – especially in central Tokyo’s 23 wards. At the Kanda River/Ring Road No. 7 facility, it takes about one minute by elevator to reach the reservoir 42m below ground.
The underground tunnel – 4.5km long and with a 12.5m inner diameter – was built over two phases from 1988, and can store about 540,000 cubic metres of water – or enough to fill 216 Olympic-size pools. When river water threatens to reach a “danger” level during a typhoon or downpour, the gates to the facility will open to allow water to flow underground. This is pumped back up above ground and into the river, where it will flow into the ocean after the rain stops and the river water level ebbs.
Construction is under way to link the Ring Road No. 7 reservoir with another 3.2km facility at Shirako River in north-western Tokyo through a connecting tunnel. When completed, the overall facility will measure 13.1km in length and have a total capacity of 1.43 million cubic metres.
TMG is considering further expanding the facility to include rivers such as the Meguro River in the south-east. Mr Mukoyama told ST that the Kanda River/Ring Road No. 7 reservoir has uses beyond flood prevention. In the drier months of December to May, about 60,000 cubic metres of water is stored in the reservoir for emergency use in case of water supply disruptions during such disasters as earthquakes. In such a scenario, the water can be pumped back up to the surface using back-up generators for public use, he said.
More News and Articles
Apr 26, 2024
News
Bothar’s cutting head innovation
The trenchless industry in Australia continues to grow and the need to provide customised solutions becomes vital for a leading subsurface contractor.
Recognising the need for advanced solutions to meet the growing …
Apr 24, 2024
News
Sustainable drainage solutions: German Start-up transforms urban water management.
Germany boasts a well-established infrastructure for managing rainwater and wastewater, yet many developing countries lack such systems. Addressing this gap, …
Apr 22, 2024
News
HDD tooling that gets the job done
Horizontal directional drilling is a dynamic process that constantly changes and adapts to suit a range of applications across utilities and infrastructure. Operators looking to get the most from their equipment …
Apr 19, 2024
News
WATCH: Overnight with SAERTEX-LINER H20 in São Paulo
Available through Pipe Core, high-quality liner SAERTEX-LINER H20 performed under pressure in São Paulo, Brazil.
Maintaining aging potable water pipe infrastructure is a constant challenge …
Apr 17, 2024
News
Immersive media provides wastewater experience in Denmark
An immersive media experience (IMX) may not be what most people want when they think about industrial wastewater, but that is exactly what visitors can expect when they visit a new installation …
Apr 15, 2024
News
Spotlight on gender diversity at Pipe Core
Since founding in 2008, Pipe Core’s team has grown across all areas of the business and is now in a position where there are more females than males across the organisation. Research published in Harvard …
Apr 12, 2024
News
New Wave of Startups Scale Innovation to Solve Global Water Challenges
Innovators from Around the World Join Xylem’s 2024 Accelerator Program to Deploy Breakthrough Innovations for Utilities and Industrial Users of Water
A new group of startups …
Apr 08, 2024
News
Integrated sustainable electricity and clean drinking water systems
Altitude Water and New Use Energy Solutions have partnered to create integrated, mobile solar-plus-water generation systems that produce sustainable electricity and clean drinking …
Apr 05, 2024
News
How to Evaluate Hydraulic Fracture Risk in HDD Design
The design of horizontal directional drill (HDD) installations often requires an evaluation of the potential for hydraulic fracture of the soil layers through which an HDD passes. Evaluating …
Apr 02, 2024
News
Historic Project Linking Rome and Vatican City Uses Advanced Technology and Local Knowledge to Keep Water Flowing
Relocation of Major Sewer Infrastructure Enables Construction of Pedestrian Link for 35 Million Visitors to the 2025 Jubilee
Water …
Mar 27, 2024
News
USU Study Looks at Water Main Break Rates in the U.S. and Canada
Report Highlights Correlation Between Material and Diameter
Utah State University (USU) has published new research on water main breaks in the United States and Canada, examining …
Mar 26, 2024
News
Update BE-21: New Material in Course and Modules on Trenchless Pipe Installation
Online training on the topic of pipeline installation in civil engineering: Trenchless technology for underground drainage construction can be a resource-efficient, …
Contact
The Straits Times
Walter Sim
Japan Correspondent
1000 Toa Payoh North
318994 Singapur
Singapore
Phone:
+65 6319-5397
Fax:
+65 6319-8275