Kind: captions
Language: en
this is the world's largest rainfall
simulator located in sucuba
Japan I know that it just looks like a
warehouse with a lot of sprinklers but
this building is incredibly
important the science conducted here
keeps tens of millions of people safe
and it's only becoming more and more
vital we were given exclusive access to
tour the facility and they even let us
experience what it's like to stand under
the most intense rainfall ever recorded
this is insane no NOP no no no no no
no Japan is a land of natural disasters
most people will think of earthquakes
tsunamis and volcanoes but it also
experiences massive typhoons which are
like hurricanes that pick up energy from
the Pacific Ocean and dump meters of
rain on the
islands yakushima Island near the
southern part of Japan is one of the
wetest places on Earth receiving up to
10 m of rain every year for comparison
the Amazon rainforest gets only about 3
m of rain per year that's three times
less than yakashima Island most of the
time rain isn't a problem the water
evaporates or seeps into the soil and is
then absorbed by plants or enters the
underground aquafer systems but too much
rain in a short period like after a
typhoon can lead to serious problems
problems that scientists working at nied
use the rainfall simulator to study and
hopefully
prevent the giant Warehouse is equipped
with 550 nozzles attached to the roof
the scientists can control the intensity
of the rain from 15 mmph to 300
mmph the most rainfall ever measured in
1 hour occurred on the 22nd of June 1947
when 305 mm of rain fell on the town of
Holt
Missouri so this Warehouse can simulate
the most intense rainfall any anyone has
ever experienced in a way that makes it
the rainiest place on Earth and honestly
I'm having a good time here in sunny
Australia so I sent veritasium producer
Peter in my stad they're going to turn
on the rain really soon so I'm running
out to uh grab my rain jacket I'm
ready
wow this is so much rain all around me
there is exactly 300 mm of rain falling
every hour we've only turned it on about
5 minutes ago and there is just so much
rain there's already puddles this is
genuinely absolutely wild I don't think
I've ever experienced anything like this
before the nozzles at the simulator
contain four holes of varying diameters
so they can produce raindrops of
different sizes and the size of the
Raindrop affects how fast it falls
you've likely experienced the kind of
rain with the big droplets that Pelt
your face or walked through a drizzle
where small drops hover like
Mist because the smaller the Raindrop
the slower it
[Music]
falls there are two forces that act on a
raindrop gravity and air resistance and
the larger raindrops have a higher
weight to surface area ratio and so they
have a higher terminal velocity so they
will be falling faster a raindrop that's
1 mm in diameter Falls at only about 2
m/s while a 3mm raindrop Falls at 6
m/s air resistance is also why raindrops
aren't shaped like cartoon raindrops
they are closer to spherical but a bit
flatter on the bottom where they
encounter oncoming air if a raindrop
gets too big it flattens out caves in in
the middle and briefly resembles a
little parachute before it breaks up
into smaller
droplets flooding is something that
Japan takes very seriously and for good
reason in July 2018 there were floods
all over the country due to the rainfall
from typhoon praon some regions of the
country received nearly 2 MERS of rain
in just 10 days and the resulting floods
were enough that more than 8 million
people had to be evacuated from their
homes over 200 people died and the
damage to property from the flooding was
more than 1 trillion yen nearly $1
billion Tokyo the capital city of Japan
is very vulnerable to flooding there are
more than a 100 Rivers crisc crossing
the city of nearly 40 million people to
prevent the rivers from overflowing
there are pipes and tunnels under the
city leading to an enormous water
storage tank in October 2019 typhoon
hagab dumped over 200 mm of rain onto
the city in under 48 Hours the
underground system diverted 12 million
cubic met of water and prevented an
estimated 1.7 billion in
damage but flooding isn't the only
problem
Japan is a very mountainous country with
many towns and Villages situated in
valleys so combined with a heavy
rainfall this creates the perfect
conditions for another
[Music]
hazard
oh oh no what
[Applause]
no the researchers at nied have
identified over 700,000 places where
landslides are a significant threat to
[Music]
homes but landslides are so complicated
there are so many factors that affect if
a landslide will occur how large it
could be how fast it will move and how
much damage it will do
not just the slope angle or the amount
of new rain but the type of soil the
minerals present and the vegetation
growing on top of the
slope this is footage from a landslide
that occurred in Norway in June of 2020
there's barely any slope angle here but
the whole area sits on a layer of quick
clay an incredibly unstable clay layer
which when exposed to intense rainfall
loses its structural Integrity becoming
a liquid in the case of this Landslide
there were no casualties though several
homes were swept out to sea the
complexity of the physics of landslides
is why the work done at the large scale
rainfall simulator is so
important the best way to minimize
Landslide damage is prevention and it's
the same for cyber security creating
strong passwords using anti-malware
protection backing up your data and
updating your operating system and
software regularly something that's
particularly useful is a virtual private
networ Network like today's sponsor
nordvpn nordvpn hides your IP address
and helps protect your online identity
Peter filmed on location in Japan and he
used nordvpn to safely access public
Wi-Fi hotspots and I am currently in
Australia and I've been using nordvpn to
watch NHL games because I think the
Canucks have a real shot at the Cup this
year something I especially like about
nordvpn is that their speeds are
blisteringly fast so it's effortless to
just keep it turned on all the time high
speeds are particularly useful when
you're connecting to streaming services
and hopping on servers in distant
locations to watch content that's only
available in those regions for viewers
of this channel use the link nordvpn.com
veritasium for a huge discount on a
2-year plan plus an extra 4 months for
free so I will put that link down in the
description there's a 30-day moneyback
guarantee so it's entirely risk-free
just go to nordvpn.com
veritasium so I want to thank thank
nordvpn for sponsoring this part of the
video and now back to the world's
largest rainfall
simulator all right I'm going to try it
without an umbrella I have a very nice
very nice jacket I'm not sure how it's
going to hold up but we're going to
try oh my God this is this is insane
nope nope nope nope nope nope nope nope
my jacket is waterproof so I was fine
but my jeans are absolutely soaked proof
to steady landslides the whole Warehouse
has a secret it
moves the rainfall simulator can be in
one of five positions um velocity is
about one
m per 1 minute 1 m per minute wow it
moves on these railway tracks every time
you move it you need to grab this
gigantic
wrench and undo the these bolts this is
the pipe that connects uh you know all
the water up to to the sprinklers there
is a number of these kind of openings in
the pipe along the line so when you move
it you just connect it to a different
part so this is the landslide testing
facility yes this is a 30° throp you can
see this this is a shallow run slide
then now you can put the soil is here
now about 1 M you would put all the sand
and all the the soil and then you'd
bring the the building
over you'd move it over here yes and
then you'd start raining on it
yes 20° this slope is 20° right so you
have a 30 a 40 and a 20 20 30 40 yes so
what causes landslides well a slope will
slide when the force of gravity pulling
it down becomes greater than the force
of friction holding it up there's a
misnomer out there that water makes it
the material slipperier so it rains and
it soaks into the ground and it makes it
slipperier that's not true water is
actually an anti- lubricant for many
materials including quartz which is our
most common uh mineral in in soils on
Earth so water doesn't make soil
slipperier but soil is porous there are
grains and there are pores between those
grains and as it rains the water seeps
into the soil the pores become filled
with water and as it keeps raining the
water pressure in the pores increases
which decreases the friction between the
grains for a slope that was already at
risk of sliding this decrease and
friction is what ultimately leads to the
slope breaking apart and sliding
downhill one thing that our mathematical
models are not very welldeveloped at yet
is determining is it going to slide
slowly or is it going to slide or maybe
flow rapidly um that's a tough one
that's so experimentation is a a great
way of getting at that and um you know
the scaler effects are huge so if many
people have a little model in their lab
you know a small scale Flume but now
you're dealing with materials you know
you're not you're you're starting to get
off scale a large large uh scale
simulation device like they have in
Japan is is really
important so how can you prevent
landslides well there are a few things
you can do like using steel beams and
mesh to Anchor the slope or you can dig
up the top layer of the soil to decrease
the slope angle and when it's expected
that a slope will slide after too much
rain Engineers drill holes into the
slope and place pipes to drain the water
out another solution is to create
catchment zones and diver I channels big
holes in the ground that will catch or
divert the landslide before it hits a
residential area trees are incredibly
effective at preventing landslides not
only do their Roots provide great
anchors they draw the water up from the
soil to be evaporated away which
effectively drains the soil and
decreases the water
[Music]
[Applause]
level where steep slopes have been
deforested for the timber industry
landslides have become more common over
the last few decades there has been a
ten-fold increase in landslides in the
forests of British
Columbia humans are really good at
causing landslides and we're shaping the
land a heck of a lot more quickly than
geological processes do so when we
excavate over here or add more weight or
more Landslide or more material over
here and that triggers landslides very
very regularly um study in Seattle from
Seattle Washington a few decades ago
showed that I think more than
85% had at least partial
human uh uh trigger if you
will while the focus of the work is
primarily on Landslide study and
prevention the simulator is also used to
test how drones fly in rainy and windy
conditions it's also used to test
self-driving cars the data is used to
improve improve the hardware and
software of how the cars detect various
objects the two main ways that
self-driving cars detect other cars
traffic lights and pedestrians is with
cameras or liar sensors in both cases
rain can decrease the visibility and
accuracy of these sensors so testing
them in a perfectly repeatable
environment helps Engineers develop
solutions to these weather
challenges in Japan the rainfall
condition is changes that now is a
recently rainfall condition is a so many
heavy rainfall is a so much short time
as the world heats up due to Humanity's
addiction to fossil fuels extreme
weather events are becoming more common
compared to 30 years ago the number of
rain events in Japan with an intensity
of 50 mmph have become 40% more common
rainfall at Double that intensity has
become 70% more common climate change
will increase the rate of flooding and
the occurrence of landslides in the
future which is why the work done at the
world's largest rainfall simulator is
becoming more and more important but I
hope that Humanity focuses its efforts
on addressing the root causes of climate
change and not just on the mitigation of
its negative
impacts