The $100BN Plan to Save Tokyo

Video narrated and hosted by Fred Mills. This video contains paid promotion for InEight.

TOKYO stands as one of the most extraordinary cities on Earth. Once a pioneer of modernisation, it introduced the bullet train when much of the world still relied on steam locomotives. It emerged as a leader in electronics long before Silicon Valley was synonymous with innovation. And it has long been a showcase of engineering marvels, a city that seemingly defies destruction.

Yet, beneath its resilient exterior lies a metropolis perpetually teetering on the edge of disaster.

Above: Tokyo faces a multitude of natural disasters.

Tokyo’s geography makes it a precarious place to live. Situated on the Pacific Ring of Fire, Japan’s capital lies at the intersection of four tectonic plates, making it one of the most earthquake-prone regions in the world. Volcanic activity is a constant threat, with 111 active volcanoes across the country. Typhoons and tsunamis from the Pacific Ocean further compound these risks.

The city itself sits on a vast plain, an ideal location for a population of over 40 million. But its open expanse also leaves it vulnerable to catastrophic natural disasters. Tokyo has been razed to the ground multiple times throughout its history, yet its engineers have rebuilt it with remarkable ingenuity.

Now, as climate change and urban density amplify these threats, the stakes have never been higher.

In December 2022, the Tokyo Metropolitan Government unveiled the Tokyo Resilience Project, a ¥17TN, USD $109BN initiative designed to fortify the city against an array of threats. This ambitious plan, set to unfold over 18 years, is one of the largest civic defence projects in history.

From reinforcing undersea cables to constructing colossal flood tunnels, the project aims to shield the city from every conceivable disaster. Evacuation routes are being mapped out with precision, and rivers are being widened to manage surging waters. A digital twin of the city—a cloud-based replica displaying real-time data—is being created to monitor environmental conditions and traffic flows.

The measures extend far beyond traditional infrastructure. Green spaces spanning over two square kilometres are being developed to provide relief during heatwaves and pandemics. Cycling routes and riverside walkways are being introduced to alleviate congestion on public transport. Meanwhile, a resilient power and communications network is in the works to prevent blackouts, ensuring that even in the worst scenarios, Tokyo remains connected.

Above: Over two square kilometres of parks are being created.

Towering on the horizon, Mount Fuji serves as both a symbol of national pride and a stark reminder of Tokyo’s volatility. An eruption could blanket the city in ash, disrupting daily life for millions. The Tokyo Resilience Project includes detailed plans to clear the city swiftly and provide refuge for those affected.

Meanwhile, the threat of earthquakes looms ever-present. Japan’s National Research Institute for Earth Science and Disaster Resilience (NIED) operates MOWLAS, a vast seismic monitoring system with over 2,000 sensors on land and undersea. This early warning network, established after the 1995 Kobe earthquake, is a crucial line of defence, offering Tokyo precious seconds to prepare for the next tremor.

But as dangerous as earthquakes are, there's one other danger which is much more predictable, which has researchers very worried because the threat of it is only getting worse.

Despite its seemingly endless sprawl of concrete, Tokyo’s identity is intricately tied to water. The decision to move the capital from Kyoto was influenced in part by the region’s abundant waterways. More than 100 rivers and canals crisscross the city, with the centre dominated by the vast, spiralling moat surrounding the Imperial Palace.

But what once made Tokyo thrive also exposes its vulnerability. Flooding is a constant and critical threat to the metropolis.

Above: Flooding was once a part of everyday life in Tokyo.

A fifth of central Tokyo—124 square kilometres—sits below sea level. To address this, the Tokyo Resilience Project has undertaken bold measures to protect the city. Sea walls are being raised to prepare for a potential 60-centimetre rise in sea levels by 2100, more than double the increase since 1880.

The challenges don’t end there. Facing thousands of miles of Pacific Ocean to the south, Tokyo endures typhoons funnelled by warm northern currents, bringing torrential rains that overwhelm its streets and waterways. While typhoons are not new, the urban heat island effect and climate change have rendered the city’s climate increasingly subtropical, with storms becoming more frequent and severe. Over the last 40 years, the number of heavy downpours in Japan has nearly doubled.

Flooding has long been part of daily life in Tokyo, and in 1992, the city launched an extraordinary initiative to combat it. The Metropolitan Area Outer Underground Discharge Channel, known as G-Cans, is a vast underground flood management system. Comprising five colossal silos, it collects floodwater from nearby rivers and channels it through a 6.5-kilometre tunnel into an immense concrete hall.

This "concrete cathedral" lies 50 metres below ground, measuring 25 metres high, 177 metres long, and 78 metres wide. Capable of pumping out 200 tonnes of water per second, the facility cost USD $2BN to build and took 17 years to complete.

Above: The Metropolitan Area Outer Underground Discharge Channel, also known as G-Cans.

But even this engineering marvel is being expanded. The TRP is doubling the capacity of the system, adding new diversion channels and tunnels to create a 13-kilometre-long network—the largest of its kind in Japan.

The construction of these colossal tunnels requires equally massive equipment. A tunnel boring machine (TBM) measuring nearly 12 metres in diameter and weighing 2,800 tonnes is carving out the new channel. This feat of engineering not only excavates but also lines the tunnel walls with reinforced concrete rings to stabilise the surrounding earth.

The TBM employs a slurry pressure system to balance soil and water, ensuring stability as it advances. Additionally, its cutter head is equipped with carbide bits, 48 times harder than standard materials, allowing it to penetrate reinforced concrete walls—a task never before attempted in tunnel construction.

Once operational, the expanded system will divert up to 1.4 million cubic metres of rainwater from Tokyo’s rivers during storms. The water is held in reservoirs until river levels subside, then discharged safely back to the sea.

G-Cans is just one part of a larger network of 28 regulating reservoirs spread across Tokyo, with seven more facilities under construction. When complete, the system will be capable of managing 100 millimetres of rainfall per hour—more than London receives in two months.

Without these systems, the consequences would be catastrophic. Businesses, homes, and critical infrastructure would face inundation, paralysing one of the world’s largest cities. By investing in these vast engineering projects, Tokyo is safeguarding not only its residents but its position as a global hub of commerce and culture.

Just before midday on Saturday, September 1, 1923, a magnitude 7.9 earthquake struck an area 50 kilometers southeast of Tokyo. Over 142,000 people died, and nearly 2 million were left homeless. The fires that followed reduced 33,000 square meters of Tokyo to ash.

Above: The 1923 Great Kanto Earthquake devastated Tokyo.

The Great Kanto Earthquake remains Tokyo's most devastating natural disaster, but events like this are a fact of life in Japan. In 1995, the city of Kobe was devastated by a magnitude 6.9 quake, and in 2011, the Fukushima nuclear meltdown was triggered by the massive Tōhoku earthquake and tsunami.

Japan’s seismic activity is measured on the Moment Magnitude Scale, where each level is ten times stronger than the previous. Anything over level four threatens property, and a quake stronger than level nine releases enough energy to power the United States for 2,000 years. Nearly 600 level-four or higher earthquakes struck Japan in 2024 alone, fueling fears of the “big one” that could rival the destruction of the Great Kanto disaster.

While earthquakes cannot be prevented, Tokyo’s resilience lies in preparation. At NIED, researchers are studying early warning signs with a 200-ton Giant Rock Friction Apparatus. This machine simulates tectonic plate slips, helping scientists understand the physics of earthquakes and gather crucial data for prediction systems.

NIED also operates E-Defense, the world’s largest earthquake simulator, capable of recreating the conditions of a magnitude seven quake. These cutting-edge facilities have made Japan a global leader in earthquake engineering.

Tokyo’s skyscrapers exemplify this expertise. The Mori JP Tower, completed in 2023, is equipped with independent energy supplies, food stores for thousands, and systems to keep running after a disaster. Its earthquake defenses include over 600 oil dampers and seismic wall dampers that convert quake energy into heat, stabilizing the structure.

Above: The Mori JP Tower serves as a safe haven during earthquakes.

Neighborhoods of fragile wooden housing, once the source of devastating firestorms during earthquakes, are being upgraded with firebreaks, underground utilities, and fire-resistant buildings. Massive sea walls protect against tsunamis, while over 400 bridges are retrofitted with earthquake protection to keep vital infrastructure intact.

The Eitai Bridge, reconstructed after the Great Kanto Earthquake, now symbolizes Tokyo’s resilience. Its modern seismic reinforcements ensure it can withstand forces from any direction, reflecting the meticulous planning behind the city’s safety measures.

The Tokyo Resilience Project is unparalleled in its scope and ambition. From underground reservoirs and sea walls to seismic skyscrapers and retrofitted bridges, the city is preparing for every conceivable disaster. Tokyo has always risen stronger after calamity, learning from its history to safeguard its future.

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Video narrated and hosted by Fred Mills. Additional footage and images courtesy of