Water-related Disasters

Hello, and welcome to Japanology Plus.
I'm Peter Barakan.

I'm in Arashiyama, an iconic spot in Kyoto
which is famous for its natural beauty.

Japan is blessed with much natural beauty,

but nature can also be cruel at times.

There are frequent natural disasters,

and many of them are related to water.

This river is quite peaceful today,

but four years ago,

that bridge was almost submerged,

and the river overflowed quite seriously.

Today we're going to look at why it is

that flooding and other water-related
disasters are so frequent in Japan,

and how people have coped
with them through history.

Japan often suffers
from water-related disasters,

many caused by heavy rain.

Over the last decade,

97 percent of the country's municipalities
have been affected.

Water-related disasters can be divided
into three main categories.

First, river flooding.

This happens just about
every year in Japan.

In 2019, heavy rain caused
by Typhoon Hagibis caused flooding

that broke through many river embankments.

Floodbanks failed at 140 sites
along 71 rivers around Japan,

and 95,000 buildings
were damaged or destroyed.

The second category
is rain-related landslides and mudflows.

These are especially common in areas of
Japan where there are steep mountainsides.

In 2021, part of Atami in Shizuoka
was hit by a mudflow.

No more than 30 millimeters
of rain fell per hour,

but over time,

water built up in the ground,
leading to a deadly disaster.

The final category is storm surges.

These accompany low-pressure
weather events, such as typhoons.

A difference in pressure causes
the sea level to rise.

With a strong wind behind it,

a storm surge
can cause significant damage.

In 2018,

during Typhoon Jebi, a storm surge
affected areas around Osaka Bay.

Much of Kansai International Airport
was inundated.

To make matters worse, a cargo ship
ran into the main access bridge.

It was 17 days
before the airport fully reopened.

Japan enjoys the blessings of nature,

but the threat of disaster is
never far away.

Today we're visiting a facility where
various types of disasters are studied.

Good morning.

Nice to meet you.

Nice to meet you too.

Our guest is Kawaike Kenji,
a professor at Kyoto University.

He studies disaster mitigation systems

that take environmental factors
into consideration.

Recently, water-related disasters
have been happening more frequently.

At this facility,
we conduct various experiments

to learn how and why those events occur.

So what kind of an experiment are
we going to do today?

Well, we have an artificial rain machine
that I'd like you to experience.

Water will fall from up there.

Right here?

Ooh.

This is around 200 millimeters per hour.

OK.

The current record in Japan is
187 millimeters per hour.

Woah.

So this exceeds the highest level ever
observed in Japan.

So...alright.

Let's give it a try.

I'm going to hold onto this
with both hands, I think.

OK, I mean, even the noise is
quite alarming, I must say.

It's...it doesn't feel dangerous.

I suspect that if this was happening
in the real world, it probably would.

In a real storm,

the raindrops would be larger,
and they'd fall faster.

The wind would be blowing too.

Right.

It would feel much more intense.

OK.

Obviously, flooding, mudslides and all
those kind of disasters

happen in many,
many places around the world,

although Japan is particularly
prone to them, I think.

There must be many reasons for that.

One reason that always
has seemed obvious to me is that

it's a very mountainous country.

As soon as you go inland from the coast,

you see quite high mountains everywhere
in this country, don't you?

Yes, that's true.

In Japan, we have lots of mountains
and few plains,

so our rivers often
have a very steep gradient.

The water carries a huge amount of
sediment down from the mountains.

That's true of many Japanese rivers,

and it makes flooding more likely.

Japan's rivers tend to be shorter
and steeper than those in other countries.

During heavy rainfall,

rivers quickly fill,
creating a significant risk of flooding.

Also, only around 30 percent of
Japan is habitable.

In many European nations, for example,

the percentage is over double that figure.

A large population—over 120 million
people—is concentrated in the plains.

Much of that land, including dense
urban areas like Tokyo, Osaka and Nagoya,

is at sea level or below.

The ground may actually be lower than
the average sea level.

Water-related disasters are more likely
to occur in such locations.

Also,
as part of the industrial development

that took place
during Japan's economic boom,

groundwater was pumped up,
leading to land subsidence.

That contributed to the problem.

And Japan's always had a rainy season,
from mid-June to late July, I suppose.

Indeed.

And towards the end of the rainy season,
in July,

areas of heavy rainfall
called "linear rain bands"

are more likely to occur.

During that season,
disasters are more common.

And lately,
typhoons are causing damage more often.

Typhoons can happen any time
between June and October.

In those months,
you can't let your guard down.

Also, rain has become more intense.

That's one impact of climate change.

It has long been said in East Asia that
whoever rules the water rules the world.

In 16th-century Japan,

warlords took steps to protect their
domains from water-related disasters.

The measures put in place
by Takeda Shingen

are held in particularly high regard.

One example is the Shingen Embankment.

Rocks were packed together to divert
or weaken strong currents.

It is believed

that Shingen was also behind
the development of these structures.

Wooden logs are arranged
in a triangular shape,

placed in the riverbed,
and weighed down with rocks.

When the water level rises,

the structures disturb and weaken
the river's flow.

This also causes an accumulation of
sediment that offers further protection.

In the 17th century,

Tokugawa Ieyasu—the warlord who united
Japan—initiated a major project.

He diverted the course of the Tone River.

At the time, the river flowed into
Tokyo Bay, and frequently burst its banks.

The river was diverted east,
into the Pacific Ocean.

The work took half a century.

Besides strengthening flood protection,

this led to new rice fields
along the river.

The project also improved water transport.

It contributed to the nation's emerging
prosperity and stability.

From the mid-19th century,

Japan began importing
the latest engineering techniques.

Concrete floodbanks and dams were built
across the country.

Disaster mitigation measures
have continued to evolve to this day.

However,

the modern era is presenting challenges
that are defeating these defenses.

The water seen here
didn't come from river flooding.

The amount of rain was simply
too much for the drainage system.

This phenomenon is unique to urban areas.

Here is a demonstration of
what happens inside the drainage system.

It is able to deal with
50 millimeters of rain per hour.

But recently,
a higher volume of rain has been falling.

Water is pushed up through the pipes.

It surges out through manhole covers,
inundating the streets.

In recent years,

this has been the cause of 90 percent
of the water-related damage in Tokyo.

OK, done up like
this I'm feeling a bit like

a combination of a fisherman
and a construction worker.

Many staircases lead underground,
from street level.

And so, when the streets become flooded,

that water flows down the stairs,
and enters the lower levels.

OK.

The people underground may have to
climb the stairs to escape.

I'd like you to see for yourself
how difficult that might be.

OK. Because when you have rainstorms
in Tokyo,

a lot of people are riding underground
trains at the time, including myself.

And it is a worry.

You wonder what would happen
if something did happen like that.

We're going to recreate what happens

when the water is 30 centimeters
deep on the surface.

Whoa.

Oh my god.

If this was happening for real,
I would be panicking.

Oh my god.

This is insane.

If I fell off this,
I'd be in serious trouble.

If this really happened
in the underground, forget it.

But as I said,

I just hate to think that anything like
that would ever happen in real life.

I would not want to go through that.

Next, let's see what it's like to
open a door during a flood.

The water is around 35 centimeters deep.

Try opening the door.

OK.

Shall I try a little...whoa, it's leaking!

It's okay.

Actually I was...I surprised myself.

I didn't think that
that was going to open,

but it's interesting...
you get it just a little bit open,

and then it gives,
and then you can open it.

When the drainage system is overwhelmed,

rainwater pools in low-lying areas.

It can bring cars to a standstill.

People have to push a car door
open from inside,

so that they can escape.

But when there's as much water as this,

opening the door
becomes a lot more difficult.

This set-up lets you experience
that for yourself.

This time the water's 45 centimeters deep!

Yeah, the water's already leaking
into the car.

Pretty alarming.

So I'll try and open the door.

Peter manages to
open the door only slightly.

Next, he'll move to the back seat,

and try the sliding door.

When the water is 45 centimeters deep,

it's similar to contending
with a weight of 60 kilograms.

This time, the door doesn't budge.

I feel exhausted after that.

Interesting though;
you can push the door open,

but the sliding door
doesn't budge an inch.

With sliding doors,
you're not actually just sliding them.

First, you need to
push the whole door out.

You push it out, then slide it.

While you're trying to do that,

the water is applying pressure to
the bottom of the door.

Pushing the entire door directly against
that pressure is very difficult.

At the same depth,

regular doors, like those next to
the driver's seat, are easier to open.

Understood.

Hi I'm Matt Alt, and this is Plus One.

On today's episode, I've come to
Chiba Prefecture, the city of Ichikawa,

about an hour from downtown Tokyo by car.

The reason I've come is because
they tell me

there is an emergency supply store here

that sells its products
in a very unique way.

How unique?

You're going to
have to follow me and find out.

Oh wow, look at this!

It's like a food truck!

Oh, hello there.

Hi, nice to meet you.

Nice to meet you too.

This is a really amazing setup.

Where did you get the idea to do this?

We wanted to bring peace of mind
to communities at risk.

So we began driving around,
selling these supplies.

This mobile sales truck is stocked
with goods for use in a disaster.

Qualified experts drive around
to low-lying areas

and show potential purchasers
how to use the products.

Have a look at this.

When it's inflated,
this becomes a solar-powered light.

It's inflatable!

Yes. And sunlight charges it up.

I see.

So the idea is that you charge
this up during the day,

and then use it at night.

Yes. You don't need mains power.

The light is entirely waterproof,
and it floats.

This is a floating backpack.

Try putting it in water.

Really?

OK.

Ready?

Oh wow, it really does float.

This is amazing.

It is! Even if you push it right down,
it'll pop back up.

Wow, so does this...can this be used
as like a lifesaving device too?

What's the purpose here?

If you're in trouble in water,

you can hold onto it to stay afloat.

But that's not all.

You can even throw it into the water,

and use it to save someone else.

It's a flotation device.

Inside, it's lined
with a waterproof material.

So it can also be filled up with water.

Oh, look at that!

Unzip this, undo the valve,

and you can release the water.

I see.

I never thought about it before,

but having a bag that can actually
carry water seems really useful.

Now let's take a look
at a cardboard toilet.

Can you show me how it's put together?

You construct the box,

and put the cardboard seat on top.

Then you add this plastic toilet liner...

...and place one of these
absorbent sheets inside.

I'll pour some liquid in.

Yep. It sucks it right up.

Look closely.

Little by little, the liquid is absorbed.

It's turning into gel.

And that's it.

The sheet has done its job.

Oh—it works!

Or at least it supports my weight.

I haven't actually tried it yet.

Excellent.

But of course,
I don't want to do that outside, do I?

You don't.

So once it's assembled,
you can put it inside this tent.

Then whoever needs to use it
can just go inside the tent.

One by one.

That makes sense.

That makes sense.

When you've finished,
you take out the liner,

and pull hard on these strings.

You wind them around,
make sure the liner is sealed,

and then dispose of it.

Very convenient.

Well, it's a long way
back to Tokyo from here,

so I guess I'd better give this a try.

But can I get a little privacy?

See you next time.

In Japan,

climate change is making natural disasters
harder to predict and prepare for.

To mitigate their impact,

new measures are being implemented
in various fields.

Here, experiments are being conducted
on two-story houses.

Artificial rain pours down relentlessly.

It builds up outside,

and begins to leak through.

Suddenly, the glass door breaks,
and water pours in.

Here's another house.

There's a lot of water outside,
but not a single drop finds its way in.

It's a water-resistant house,
designed to cope with flooding.

It was developed by a company in Shizuoka.

This is a water-resistant house.

We can go inside and try it out.

Let's begin.

A huge volume of water pours
into the area around the house.

Just five minutes later,
the water has reached window level.

In a regular house, water would already be
coming up through vents and pipes.

The toilet would be overflowing.

But this house makes
use of special valves.

They stop water from coming in.

And the house has another line of defense.

The house avoids damage by floating.

If the water level exceeds one meter,

the house and its foundation
begin to float.

If it's properly sealed,
the whole building will simply float.

The house is watertight,
and is equipped with buoyancy devices.

But what stops it from floating away?

The building's foundation is attached to
four poles by steel cables.

This set-up holds everything in place.

The cables are fitted
with special springs.

When the water recedes, the house
moves back to its original position.

The house can cope
with water up to 5 meters deep

that's flowing at up to
11 kilometers per hour.

There is growing demand for structures
like this in flood-prone areas.

Next, a car heading straight into the sea.

It floats!

The car can move forward,
and even make turns.

It's an electric vehicle,

designed for use in emergencies
when roads are inundated with water.

It was developed by Tsurumaki Hideo,
the founder of a start-up near Tokyo.

Work on the car started in 2013,
and development took four years.

Every opening has been sealed,

and inside the body are resin components
like those used in boats.

This allows the car to float
for up to 24 hours.

Another remarkable feature is
the front wheels.

As they turn,

they draw in water and expel it backwards,

propelling the vehicle forwards.

On a full charge, the car can move around
in water for six hours.

Due to climate change, water-related
disasters have become more common.

My dream is to save lives.

We've been hearing warnings about climate
change for quite a lot of years now.

And I think a lot of people thought that
it was still some distance down the road.

Obviously, that is no longer the case;

it's seriously with us already.

What can we do about it,
and...in Japan in particular, I suppose,

because we're talking about Japanology.

There are various things we can do
with technology and with knowhow.

In terms of technology,

we can improve the sewers and rivers
that carry rainwater.

We can dig large tunnels underground

to augment the amount of water
that rivers can carry away.

We can also increase the amount of
rainwater absorbed into the ground.

One way to direct water
underground is to use permeable paving.

The rain trickles down through
gaps in the asphalt.

Similarly, more people are
installing dry wells.

Rainwater in gutters flows into the wells
and from there into the ground,

rather than into a sewer or river.

Some local authorities offer financial
support for the installation of dry wells.

In our house, we've got a big tank
that's attached to one of the drainpipes.

So instead of the water going underground,
it goes into the tank.

We've diverted it.

And we use that water
for watering plants and stuff.

So it's quite useful.

I hadn't realized, though,

that that was such a big problem...
of all the water going underground.

In terms of knowhow,
examples include better hazard maps,

and better ways to keep people informed
about real-time conditions.

We're using all sorts of new techniques

to strengthen our ability to deal
with water-related disasters.

That process is ongoing.

Also, some locations have suffered from

disasters again and again
throughout history.

We need to make use of the local knowledge

that has been passed down through
the years in those locations.

I think, probably like a lot of people,

I see these things happening
on the television news,

and I think, "Wow, that's horrible,"

but it's also something
that's happening to someone else,

and you don't actually feel it,
so there's not a sense of reality so much.

Coming here today, and especially
with that thing with the stairs,

and the car thing as well,
that was seriously scary.

And you realize that
if something like that did happen,

it could very well be me,
and that is a sobering thought.

But at least now you're better prepared.

Thank you very much.
It's been very interesting.

Thank you very much.