Tokyo broadens underground 'cathedral' complex to counter climate change rains

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Just after 5 a.m. on August 30, water started flooding a large underground chamber called the cathedral just north of Tokyo. The gushing water, recorded by security cameras, was the rain that was drenching the capital area as Typhoon Shanshan lashed southwest Japan, 600 km (373 miles) away.

The cathedral and its huge network of tunnels did their task: they prevented a vulnerable river basin in the metropolis from flooding. But as worldwide warming triggers more severe weather condition, authorities are needing to offer the system a significant upgrade.

As the temperature increases, the quantity of water vapour in the environment boosts, resulting in fairly larger quantities of rainfall, stated University of Tokyo professor Seita Emori, who belongs to an environment science group that won a Nobel Reward in 2007.

We expect that previously unseen amounts of rain will fall as the temperature level increases in the future, he added.

Japan is susceptible to many natural disasters, from earthquakes and volcanic eruptions to typhoons and landslides. And like much of the world, the country is dealing with unprecedented weather due to international warming.

This summer was the hottest ever since records started in 1898, while record rains in northern regions resulted in disastrous flooding in July, according to the weather condition firm. In Tokyo, unexpected, violent storms called guerrilla showers have end up being significantly common.

The cathedral complex, formally called the Metropolitan Outer Location Underground Discharge Channel, took 13 years and 230 billion yen ($ 1.63 billion) to build. Given that coming online in 2006, it has currently avoided more than 150 billion yen in flood damage, the land ministry quotes.

In addition to its engineering ingenuity, the complex is a. popular traveler spot and filming location. The spacious area. has the capacity to hold the water in nearly 100 Olympic-sized. pool.

Inside are 59 huge pillars, each weighing 500 tonnes (551. heaps) and stretching 18 metres (59 ft) high. When close-by rivers. flood, the overflow courses through 6.3 km of enormous. underground tunnels before gathering in the tank.

Coming down about 6 floorings to the bottom of the chamber is. a transcendent experience. It has its own microclimate, much. cooler than the surface in the summertime and warmer in the winter season. Clouds of mist obscure the top of the pillars.

The dim interior, punctuated by spears of natural light from. apertures in the ceiling, and towering pillars evoke an ancient. religious structure, generating names such as the. cathedral, the shrine or the temple.

The drop of the No. 1 shaft is deep and broad adequate to. easily hold the Statue of Liberty.

The system began four times in June, more than all of. last year. During Hurricane Shanshan, it recorded enough water to. fill the Tokyo Dome baseball stadium practically 4 times, previously. pumping it securely into the Edogawa River and out to sea.

Compared to years past, there's a tendency for a great deal. of rain to come down simultaneously in what we call guerrilla. rainstorms, said Yoshio Miyazaki, the land ministry authorities in. charge of the complex.

If this center didn't exist, the water levels of the main. Nakagawa River and its tributaries might rise much higher,. leading to flooding of homes and even deaths, he said.

However, the system couldn't stop the inundation of more. than 4,000 homes in the river basin from heavy tropical storm rains in. June 2023. Those floods prompted authorities to start a. seven-year, 37.3 billion yen job to bolster levees and water. drain in the location.

And closer to the centre of Tokyo, another major project is. underway to link channels that take in overflow from the Shirako. and Kanda rivers. When completed in 2027, it will bring. floodwater about 13 kms underground out to Tokyo Bay.

Tokyo's drain network is designed to manage rainfall of up. to 75 mm per hour, but significantly there are localised storms. reducing as much as 100 mm, overtaxing the system, stated. Shun Otomo, a construction website manager for the task.

For instance, if there is a short-lived downpour in the Kanda. River basin, we can tap the watershed capacity in basin locations. where it isn't drizzling, Otomo stated. We believe that will be. effective against these guerrilla rains..

(source: Reuters)