#24 Storm Surges

Japan has a long history of natural disaster.

Now, the power of science has helped it to overcome them.

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Sciece that Can Save Your Life.

A storm surge is a rise in sea level that can cause large-scale flood damage.

In 2018, Kansai International Airport, built on an artificial island in Osaka Bay, was flooded.

Waves in excess of 5 meters overcame the seawall, shutting down the airport for 17 days.

In 2012, a storm surge flooded subways and electrical substations in New York City.

The city was paralyzed and the damage exceeded 70 billion dollars.

For Japan, which is surrounded by the sea on all sides, storm surges are an unavoidable danger.

With tremendous destructive power, they are causing damage not only in Japan but all over the world.

But why are storm surges becoming more destructive?

In this episode, we will take a closer look.

We spoke with Dr. Tomokazu Murakami, who has been researching storm surges in Japan for many years.

Why do storm surges occur?

Storm surges can occur during typhoons, due to the "suction effect" of atmospheric pressure
and the "blowing effect" of the wind.

When a typhoon approaches, the air pressure drops, and the sea surface is sucked up.

Then strong winds blow the seawater toward the coast, causing a storm surge.

If it coincides with a high tide, the sea level will be even higher.

In 1959, Typhoon Vera caused Japan's worst storm surge disaster in 150 years.

More than 5,000 people were killed.

The storm surge was approximately 3.6 meters high.

Of this, 50 centimeters was due to the suction effect, and the remaining 3.1 meters was due to the blowing effect.

The blowing effect has a greater impact
on the storm surge height.

Wind strength and direction
are the two important factors.

Strong winds push seawater
towards the land, raising the sea level.

In Japan, typhoons come from the south.

If seawater is funneled into a narrow south-facing bay, it will cause the sea level to rise.

Osaka, Nagoya, and Tokyo - Japan's large cities - are at high risk of a storm surge due to their location at the head of bays.

Therefore, seawalls are being built along the coastline to protect against storm surges.

The path of the typhoon is also important.

In the northern hemisphere, where Japan is located, typhoons move in a counterclockwise direction.

On the east side of the typhoon the wind becomes stronger due to a combination of the movement speed and the wind speeds.

This is the path of Typhoon Vera.

As the typhoon passed over the western side of the bay, strong winds blew across the sea toward the land, causing the sea level to rise and increasing storm surge damage.

Typhoons get energy from water vapor.

As the sea temperature rises, water vapor
increases, making the typhoon larger.

The bigger the typhoon, the more damage
is caused by the storm surge.

They will become more dangerous
as climate change causes sea temperatures to rise further.

Climate change might cause storm surges to become bigger and more powerful.

What would happen if a massive storm surge occurred?

Murakami can simulate the damage that would be caused by a massive storm surge.

How will climate change affect storm surges?

I'm researching what kind of typhoons and storm surges
will occur at the end of this century if moderate warming continues.

Murakami predicts that, due to climate change, there could be a massive typhoon far more powerful than Typhoon Vera, with wind speeds of 53 meters per second.

A huge "super typhoon" will occur.

A super typhoon?

If the super typhoon passes slightly further east than Typhoon Vera, Murakami predicts that the wind blowing into the bay would become stronger,

causing a massive storm surge unlike any we have seen before.

The height of the storm surge caused by the super typhoon would be 6.9 meters.

That's more than 3 meters higher than the storm surge of Typhoon Vera.

If this kind of storm surge were to hit Nagoya Port, what kind of damage would it cause?

According to Murakami's simulation, at 6.50 pm, the storm surge would hit Nagoya Port, flooding the city.

After ten minutes, the entire southern area would be submerged by more than a meter of water.

The flooding would not immediately spread to the northern part of the city because of the seawall.

However, twenty minutes later, the seawall would be breached, flooding the area by more than two meters.

In just 30 minutes, the city would be submerged by more than two meters of water.

And the danger of storm surges is not just limited to the raging flood waters.

Shipping containers, automobiles, and other objects in a port can also become threats.

Murakami is also developing a virtual reality system so that people can understand the dangers of storm surges.

We can simulate a storm surge in VR.

Why don't you try it?

You're standing on a wharf at Nagoya Port,
with a 360-degree view.

The water is coming in so rapidly.

Cars are floating past!

There's so much debris.

The whole are has flooded quickly.

I can hardly believe that
I'm back on solid ground.

The storm surge height is over your head.
And lot so debris isfloating past.

This is the kind of experience you'd have.

So there's danger not just from the water,
but also from the objects floating past.

During Typhoon Vera in 1959, lumber from Nagoya Port
was swept up and hit homes, causing extensive damage.

How will storm surges grow in size and power as climate change progresses?

The latest IPCC report predicts that sea levels will rise approximately 60 centimeters by 2100, and there is concern that storm surge damage will become more serious.

Dr. Tomoya Shimura is an associate professor at Kyoto University.

In 2022, Shimura and his colleagues published their latest research, which included predictions of the scale and frequency of future storm surges if climate change continues.

How do they predict future storm surge damage?

This is a graph of predicted storm surges in Osaka Bay.

The vertical axis is storm surge frequency.

The horizontal axis represents storm surge height.

The blue line represents storm surges under current climate conditions.

The red line represents storm surges at the end of the century affected by climate change.

Let's compare the sea level of a major storm surge, which is said to occur once every 50 years.

If the current climate remains the same, the height of the storm surge would be 2 meters.

However, if the climate gets warmer, it is predicted to rise to 2 meters and 50 centimeters.

This shows how climate change could affect storm surges.

With a 60-centimeter rise in sea level plus a storm surge of 2 meters 50 centimeters, waves in excess of 3 meters are possible by the end of the century.

Shimura also warns that by the year 2100, if temperatures have risen by 4°C, once-in-50-year storm surges that cause major disasters will increase in frequency.

Major storm surges,
which previously occurred once every 50 years, would increase to once every 10 years.

Stronger storm surges are a major threat.

If one were to hit Tokyo Bay, where many people and buildings are concentrated, the damage would be extraordinary.

What measures can be taken to counter a storm surge in Tokyo Bay?

We spoke to Horikawa Seiji, who works to protect Tokyo against storm surges.

What is being done to protect Tokyo
against storm surges?

Tokyo is extremely susceptible to storm surges, so seawalls, floodgates, and drainage pump stations
have been constructed to protect Tokyo's residents.

The cornerstone of Tokyo's storm surge protection plan is Japan's largest seawall, which is up to 8 meters high in places.

The 60-kilometer long seawall has been built along the coastline to protect against storm surges.

Where the seawall is interrupted by canals and waterways, a floodgate is installed, which is closed by remote control when a storm surge arrives.

But are the current measures enough, in the face of storm surges that will grow in size and power as a result of climate change?

Are there any new measures you are working on now?

The mean sea level may rise and
typhoons may become stronger, so we're making plans to
raise the seawall height.

The Tokyo Metropolitan Government has announced the country's first plan to raise the height of the seawall in anticipation of rising sea levels and massive typhoons caused by climate change.

According to the plan, about 30 kilometers of Tokyo's seawall will be raised.

Construction will be carried out in stages in order of priority, to be completed by 2100.

In addition, some local governments are making their own plans for urban development that can withstand flooding.

Tokyo's Katsushika City is developing flood control measures, making sure that some taller structures have space on upper floors that residents can evacuate to if the area is flooded.

They plan to implement this in schools, government offices, and other facilities by 2050.

Tokyo, the capital of Japan, is transforming itself into a place that is more resistant to flood damage.

Unlike earthquakes and tsunamis which occur suddenly, storm surges can be predicted to a certain extent by monitoring weather information.

It's very important to evacuate immediately, and to decide upon a suitable evacuation site with your family and loved ones well in advance.