TOKYO'S UNDERGROUND TEMPLE: A FLOOD COPING MECHANISM

 

Underground Tunnel with gigantic Pillars

Japan has earned a global reputation for its innovative civil engineering projects and its ability to construct massive structures and unique architectural concepts. Tokyo, as one of the world's busiest and most creatively dynamic cities, faces the challenge of protecting itself from the destructive forces of typhonic storms and the recurring threat of water overflooding. Did you know? Tokyo's geographical location, with more than five small and large rivers converging at its entry point, makes it particularly vulnerable to these natural hazards. Adding to the complexity of the situation is Japan's status as one of the rainiest countries globally, receiving an average annual rainfall of approximately 63 inches.

As the bustling city of Tokyo peacefully sleeps through the peak monsoon night, a silent underground marvel is hard at work, ensuring the safety of thousands of lives and the protection of their valuable properties in the Tokyo Lowland. This incredible feat comes into play when the Northern Tokyo Basin faces the threat of rising water levels, transforming the surrounding settlements into potential danger zones. In response to this recurring risk, Japan's disaster risk management has unveiled an ingenious solution—a scheme designed to store and efficiently drain excess water through a network of tunnels meticulously constructed beneath the city's core.

Flood Control Mechanism

This subterranean system comprises an impressive 6.4 kilometers of tunnels that delve as deep as 50 meters below the city's surface. To put this into perspective, this depth is nearly as significant as the height of the Statue of Liberty. These tunnels interconnect five colossal silos, each towering at an impressive 65 meters in height and stretching 32 meters in width. The heart of this engineering masterpiece is the "Underground Temple," a monumental reservoir of epic proportions, measuring 25.4 meters in height, 177 meters in length, and 78 meters in width. Supported by 59 sturdy pillars, this subterranean sanctuary serves as the central hub of this remarkable infrastructure. The system functions as follows: Rainwater collected from the city's drainage networks is channeled into the tunnels, where it serves as flow controllers. These tunnels are strategically designed to manage the water's flow. As the water accumulates, it is efficiently directed into the flood chamber. When the water level within this chamber reaches a specific threshold, a set of four turbines come to life. These turbines, each powered by jet engines akin in size to those found on a Boeing 737, spring into action, expelling the water from the chamber at a remarkable rate of 200 cubic meters (equivalent to 53,000 gallons) per second. The discharged water is released into the Edogawa River at a juncture where it can be safely transported to the ocean, without posing any additional flood risk to the city.

This underground engineering marvel, resembling a cathedral in its grandeur and functionality, stands as a testament to Tokyo's commitment to protecting its population and safeguarding against the annual threat of flooding. It exemplifies the innovative and forward-thinking approach that has become synonymous with Japan's civil engineering prowess.

Tokyo intermingled with different rivers

The massive project in Northern Tokyo Lowland, which cost approximately 2 billion dollars and was completed in 2006 after 13 years of effort, might raise questions about why a government would allocate such a substantial portion of its economy to construct such a grand architectural wonder. However, the investment in this project was not just a matter of extravagant spending. The Northern Tokyo Lowland holds deep cultural significance, dignity, and beauty. Throughout history, this lowland has been depicted as a victim of devastating floods in ancient paintings, pictures, and books. The catastrophic impact of these floods has been etched into the collective memory of the region. In response, the government embarked on this ambitious endeavor to mitigate the recurring threat of flooding. Today, this once-vulnerable area has transformed into a vibrant space for evening hangouts and leisure activities, thanks to the protective cathedral structure that lies beneath its surface. It has become a bustling and popular destination for both locals and visitors. Nonetheless, the need for further precautions and adaptations is evident. Rising sea levels and changing rainfall patterns in the region necessitate continuous efforts to safeguard against future flooding and protect the invaluable cultural heritage of the Northern Tokyo Lowland. Japan must continue to invest in innovative solutions and backup measures to ensure the long-term resilience of this remarkable landscape.