introduction ,importance ,of g cans flood control tunnels.

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1.0 INTRODUCTION
The Tone, Are and Edo Rivers had been terrorizing the people of greater Tokyo for
generations with their periodic monsoon-season flooding and Typhoons. In September 1991,
the worst storm to strike Japan in 30 years. 30 000 homes and 100 square kilometres (25 000
acres) of land in the low-lying northern suburbs of Tokyo were flooded, causing a total of 52
deaths in Japan.
The question arises How can we prevent flooding and water damage in area like
Tokyo ,the answer was not to concentrate just on river improvement but instead to create
comprehensive flood control measures for the basin as a whole .Comprehensive flood control
measures include river and sewage system improvements but also the construction of special
storage facilities that can store runoff water in the urban area and prevent it from flowing into
rivers causing them to overflow their banks .That’s why flood control channel storage
facilities have been built.
To protect the city’s 13 million residents from heavy rainfall and tropical storm
floods, The simplest solution would have been to build a reservoir. But the question facing
urban planners was :- How to build a reservoir In a city twice as dense as New York ? The
answer : Build it underground. The results were Metropolitan Area Outer Underground
Discharge Channel. Completed in 2006 G Cans gathers the overflowing floodwater from the
rivers in Tokyo such as OochiKotone, Kuramatsu, Nagakawa and Arakawa, and drains it into
the Edogawa River. The place is also used for guided tours or filming movies and
commercials, although this may suspended depending on the weather.
Some people have suggested that this ¥230 billion project is something of an overkill –
perhaps designed more to line the pockets of Japan’s construction industry than to keep
anyone’s feet dry, but there was certainly a need for something. In 1991, two years before
construction began, 30,000 homes around the northern fringes of Tokyo were flooded by a
typhoon, and it was predicted that a once in two hundred year extreme deluge would flood
almost 100 subway stations. G-Cans took 17 years to build, and since its completion in 2009,
it’s massively reduced flooding. No doubt Tokyo residents whose homes frequently used to
end up underwater think it’s money well spent.

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2.0 FLOOD
 A flood is an overflow of water that submerges land that is usually dry.
 Flooding may occur as an overflow of water from water bodies, such as a river, lake,
or ocean, or it may occur due to an accumulation of rainwater on saturated ground in
an areal flood.
 Floods can also occur in rivers when the flow rate exceeds the capacity of the river
channel, particularly at bends in the waterway. Floods often cause damage to homes
and businesses if they are in the natural flood plains of rivers.
 Some floods develop slowly, while others such as flash floods, can develop in just a
few minutes and without visible signs of rain.
 Flood caused by river overflow has the potential of sweeping everything in its path
downstream. Lake and Coastal flooding occurs when large storms or tsunamis causes
the water body to surge inland.
 The immediate impacts of flooding include loss of human life, damage to property,
destruction of crops, loss of livestock, and deterioration of health conditions owing to
waterborne diseases.
2.1 JAPAN’S HISTORY WITH FLOODS
Tokyo, and the rest of Japan, has a long history of devastating and deadly floods. A storm in
1910 destroyed 4.2% of the nation’s GDP. And storms throughout the 20th
century left the
rapidly urbanizing nation’s cities and towns underwater. And just last year, floods ravaged
cities in Japan’s northern regions.
Fig no - 1

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3.0 PROFILE
 Address:- Showa in Tokyo to Saitama, outskirts of the Greater Tokyo Area.
 Purpose: - Flood Control
 Dimension of silo: - 65 m height, 32 m diameter.
 No of silos :- 5
 Dimension of tunnel :- 6.3 m long
 Dimension of water tank: - 25m height, 180 m length, 80 m width.
 No of turbines :- 4
 Type of Turbine:- Jet engine turbine.
 No of pillars in water tank :- 59
 World record:- world's largest underground flood water diversion facility.
 Engineer :-Japanese Institute of Technology and Engineering Sewage
 Owner :- Government of Japan
 Construction Cost:- $3bn
 Construction started:- 1992
 Project Completion :- 2009

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4.0 WHAT IT IS & WHY IT IS MADE?
Ever wonder why Tokyo does not flood?
Next time when you are walking around the Japanese capital, stop for a minute to consider
this, Just 50 meters below the ground is a labyrinth of tunnels and massive pumps that can
remove 200 tons of floodwater every second.
It has been described as the biggest underground man made drainage system in the world.
With around 30 percent of Tokyo’s population living below sea level, mostly along Tokyo
bay or many rivers that feed into it, the metropolis has had a long history of disastrous
flooding.
As the capital city grew and Japan prospered, protecting the world largest metropolitan
economy and its inhabitants – over13 million in Tokyo today and more than 36 million in the
greater metropolitan area – become a national priority.
The Tone, Are and Edo Rivers had been terrorizing the people of greater Tokyo for
generations with their periodic monsoon-season flooding and Typhoons. In September 1991,
the worst storm to strike Japan in 30 years. 30 000 homes and 100 square kilometres (25 000
acres) of land in the low-lying northern suburbs of Tokyo were flooded, causing a total of 52
deaths in Japan
The simplest solution would have been to build a reservoir. But the question facing urban
planners was: - How to build a reservoir In a city twice as dense as New York ? The answer :
Build it underground. The results were Metropolitan Area Outer Underground Discharge
Channel, also G-Cans, and more recently the Furukawa Underground Regulating Resulting
Reservoir.
The Metropolitan Area Outer Underground Discharge Channel gathers the overflowing flood
waters from rivers in Tokyo, such as OochiKotone, Kuramatsu, Nagakawa and Arakawa, and
drains it into the Edogawa River.

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fig no -2
The aim was simple: to take all the excess rainwater from typhoons and floods away before it
can cause any damage. The way it was implemented is also simple – they built a big drain.
But the enormity and engineering complexity of the construction is staggering.
Under the floor of Tokyo, underground, unfolds a landscape worthy of any great imagination,
the G-Cans Project, the sewage of the city.
Started in 1992 at a cost of 1,500 million euros, was built to avoid the heavy rains, especially
in times of Monzón, and even a Sutnami, can cause major flooding in the Japanese capital,
for the purpose of bone to collect enormous amounts of water.
The place is also used for guided tours or filming movies and commercials, although this may
be suspended depending on the weather.
4.1 LOCATION:-
The government of Japan has made possible this feat through the Japanese Institute of
Technology and Engineering of sewage, which together with the private sector has built a
veritable underground city in Edogawa City, Saitama region, one of the great neighborhoods
or areas of Tokyo.

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5.0 WHAT IT DOES & HOW IT WORKS?
The metropolitan area outer underground discharge channel is not only equipped with temple
like water tank but also has shafts and a massive underground waterway connecting to rivers
in the region ,the total length reaches 6.3 km.
5.1 DUCT
When river water exceeds a certain level it starts flowing into ducts
Fig no -3

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5.2 SILOS
It has 5 silos with a diameter of 32 meters and 65 meters in height, connected by tunnels
along the 6.3 km.
The water been channelled underground through the shaft (5 in all).
These shafts are big enough to fit the space shuttle or the statue of liberty.
Fig no - 4

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5.3 TUNNEL
 Total length :- 6.3 km
• The water in the shafts then flow to the underground tunnel ,the tunnel is about 10m
in diameter ,it was excavated by a massive shield machine a technology in which
Japan is a world leader .
• The tunnel was bored using the shield method in order to avoid distortions due to its
depth. The work included excavation, construction of lining and muck transportation.
• The vast diameter of the tunnel also necessitated the application of a closed type
slurry shield method.
• Modern technologies were applied for the secondary lining of the tunnel to cut the
cost of construction.
• Water-tightness is maintained within the tunnel with the help of internal water
pressure reacting type segments.
Fig no - 5

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5.4 THE PRESSURE ADJUSTING TANK
 The main tank measures 180 meters long and 80 meters deep b 25 meters in height
(about the size of soccer field ).
 When even more water drains into the channel, it is sent to the tank designed to
adjust water pressure.
 The depth of the storage tank is equivalent to height of fifth or sixth floor of building.
 It is the space almost looks like a Greek temple.
 Visitors can tour the pressure adjusting tank after listening to the explanation of the discharge
channel.
Fig no - 6
5.5 COLUMNS
Each of its 59 columns weighs 500 tons and all are connected to 10MW pump capable of
moving 200 tons of water per second to the Edogawa River.

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5.6 CHANNELS AND TURBINES
 It can move its channels to 44 million liters. The system is powered by 14,000
turbines which can pump up to 200 tons of water per second. Each turbine uses the
same energy as the engine of a Boeing 737.
 These giant aqueducts are in operation when the rainfall exceeds the limit that can
generate these floods and excess water are transported mainly to the Edogawa River
and several smaller rivers along 6.3 kilometers
 When the water level in the tank rises, modified jet turbine pumps go into operation to
discharge water from sewer system.
 When all four pumps are operating, 200 cubic meters of water (equal to 25-m
swimming pools) can be discharged per second.
Fig no - 7

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• Water is discharged into a large and wide Edogawa river through a sluice.
• Water in the silos and tunnel is discharged by pumps installed in each silo after the
rain stops.
• Number 3 and no 5 shafts have a handle a large amount of water so their structure is
designed spiralling to drive the water to the walls using centrifugal force
• This slows the water and reduces impact when it hits the bottom of the shaft.
Fig no -8
6.0 STRUCTURES AND MATERIALS
The excavation is an extreme example of cutting edge technology .Its engineering is most
innovative structures and materials ,combined with tons of concrete .
the tunnel is about 10m in diameter ,it was excavated by a massive shield machine, a
technology in which Japan is a world leader .

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7.0 IMPACT ON URBANIZATION
Tokyo and the surrounding area are much safer. The risk to homes, businesses and public
services has reduced significantly. Making the area safer has encouraged more growth and
even more urban sprawl. This is creating new problems.
Super levees designed to create public walking areas and shopping centers have played a part
in new developments moving into areas that are historically flood prone. It seems the system
designed to protect Tokyo from floods has been so successful it is encouraging growth into
danger areas still relatively unprotected.
7.1 STILL A THREAT
Continued urban expansion, the recent rise in storms across east Asia, and the prospect of
further changes from climate change has city planners worried. Particularly when it looks like
the system is being overwhelmed in some areas.
Video shot in 2011 by a Tokyo resident of the above ground drain systems (supported
underneath by the G-Cans Project) during a typhoon shows what the city is still facing.
8.0 THE FURUKAWA RESERVOIR
In 2008, Japanese urban planners recognized that increased urban sprawl required a flood
control solution beyond the G-Cans. The Furukawa Reservoir would utilize old and new
concepts to protect the fast growing metropolis.
Similar to the above ground discharge waterways, the system would focus on moving water
from flood areas into rivers that could carry the water to the ocean. Instead of giant cisterns,
the system would use 3.3 kilometers of 7.5 meter diameter tunnels. But like the G-Cans
system, the Furukawa project would be entirely underground.
“What makes this system particularly noteworthy is just its scale, because it’s underneath one
of the largest cities in the world,” said Patrick Lynett, a civil engineering professor at the
University of Southern California in Los Angeles. “It allows them to have this flood control
out of sight.”

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“Japan has no choice. With the lack of space they have, they have to come up with some
ingenious way of doing this,” Marcelo H. Garcia, director of the Ven Te Chow Hydrosystems
Laboratory at the University of Illinois at Urbana-Champaign, told the Japan Times.
The project should be completed later this year. It is a feat of construction only matched by
its G-Cans peer. Starting with its connection to above ground water collection systems.
fig no -9
When finished, water will be able to be pumped away from metropolitan areas, protecting
lives and property.
The full capacity of the Furukawa Reservoir is expected to surpass 135,000 cubic meters of
water, about the equivalent of 54 Olympic-size swimming pools.
8.1 A LESS WATERLOGGED FUTURE
Completion of the Furukawa Reservoir is the second of three major underground flood
control projects in Japan’s capital region. In the next few years, a third system featuring
another 3.2 kilometers of massive tunnels in the northwest of Tokyo will be complete.
While the cost of these systems may not be reasonable for most countries, the concepts and
lessons learned will be essential in a more and more urban world facing increasing threats
from climate change.

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9.0 VISITING G CANS THE TOUR
 Naturally for such an awesome spectacle, the Water Discharge Tunnel on the
Outskirts of the Metropolitan Area has attracted great tourist interest. Visitor numbers
are limited for the regular tours (in Japanese only) and advance bookings are essential
 Upon arrival at the site one registers in the visitor Centre, where a wide variety of G-
Cans related displays are on show. At the designated time a tour guide arrives with
clever personal speaker system to introduce the tour.
• Visitors can tour the pressure adjusting tank after listening to the explanation of the
discharge channel.
• The place is also used for guided tours or filming movies and commercials, although
this may be suspended depending on the weather.
• Tours of G-Cans are popular with people of all ages, including plenty of children.
They’re conducted in Japanese, but you won’t miss much as the commentary is really
boring and repetitive. Each tour starts with a video and a look at an exhibition, before
getting to the good part – entry to the temple. You go in through a small concrete
building that slants into the ground. Inside a staircase winds down and down,
eventually emerging on one side of the giant chamber, from where you can descend to
the floor. You’re not allowed inside the silos or the tunnel – they’re for employees
and VIPs only – but you do get a good view of one silo, which is adjacent to the
temple.
• Tours run three times a day, Tuesday to Thursday, and last an hour and a half. They
can be booked via the official website, but you must be accompanied by someone
who can speak Japanese, so they can translate evacuation instructions in case of an
emergency. Tours begin at the pump station in Kasukabe City, just meters from the
banks of the Edogawa river. It’s about 35 kilometers north of central Tokyo, and can
be accessed from Minami Sakurai Station on the Tobu-Noda line. The journey takes
around an hour and ten minutes by train, then it’s around half an hour’s walk.

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Fig no -10
Fig no - 11

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10.0 CONCLUSION
• Flood tunnels are an important part of flood and storm water management system.
They are used where space is limited – often in urbanised areas such as Tokyo, or in
Kualur Lumpur.
• The Metropolitan Area Outer Underground Discharge system was built to handle
flooding from monsoon-season typhoons and has been used over 200 times.
• Government figure said, the project likely saved around 430 million dollars in
property damage alone since it become fully operational.
• The metropolitan area outer underground discharge channel provides a cost effective
solution
• Around the world there are regions suffering from flood damage much like Japan,
with its introduction in Indonesia this technology is starting to aid in global flood
control efforts.

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REFERENCES
• "LAIR OF THE BALROG". Accessed 10 January 2015
• Jump up^ "CNN How giant tunnels protect Tokyo from flood threat".
• Jump up^ "G-Cans: Tokyo's Massive Underground Storm Drain".
• Jump up^ "G-Cans Project, Kasukabe, Saitama, Greater Tokyo Area,
Japan". Retrieved 10 January 2015
• Jump up^ http://www.ktr.mlit.go.jp/edogawa/gaikaku/english/index.html
• Jump up^ "Catalyst: Tokyo Flood Prevention - ABC TV Science". ABC - Australian
Broadcasting Corporation (Video Documentary). 2014-10-23. Retrieved 2015-03-20.