Kasukabe Underground Flood Protection Tank
The Kasukabe Underground Flood Protection Tank (aka G-Cans) is the central flood protection facility for eastern Saitama Prefecture and parts of north east Tokyo.
Kasukabe Underground Flood Protection Tank (aka G-Cans) 首都圏外郭放水路, 春日部市
by Johannes Schonherr
The official English name for whole of the giant installation is the Metropolitan Area Outer Underground Discharge Channel. Located on the outskirts of Kasukabe City in Saitama Prefecture, it is a flood protection facility for eastern Saitama Prefecture and parts of north east Tokyo, namely, Adachi, Katsushika and Edogawa wards.
Kasukabe Underground Flood Protection Surge Tank, Saitama
Open to the public is only the cathedral-like underground surge tank next to the bed of the Edogawa River, right at the border to Chiba Prefecture, commonly known as the G-Cans.
It is an impressive sight indeed. That booking a visit can be a bit tricky only adds to its lure.
Background
But before I go into the details of a visit, I should provide a little background. Eastern Saitama Prefecture is located in the so-called Nakagawa Basin. It is low-lying land, below the level of the wide Edogawa River, and several small rivers, the Nakagawa being one of them, run through it.
The area has traditionally been very flood-prone, especially during the snow melt period in the mountains where the rivers originate and even more so as a result of the frequent typhoons that hit the area. Farmers often lost their harvests to the floods, but they were of little concern to the authorities.
From the 1960's on, however, the Tokyo Metropolitan Area began to extend into the Nakagawa Basin. By the 1980's, the farms had been almost completely replaced with suburban housing and industrial facilities. New train lines spread out and the real estate bubble of the late 1980's created a feverish housing market in the area; but little thought was given to the flood danger the prospective buyers faced.
Water containment silo seen from the surge tank
Kasukabe pump station and Ryu-Q Kan visitor center, Kasukabe Underground Flood Protection Tank (aka G-Cans), Saitama Prefecture
Flood Control
As a result, the area repeatedly became the victim of serious flooding, causing huge financial losses for a vital part of the economy of the Tokyo Metropolitan Area.
Something had to be done. The man-made problem of settling a huge population in a flood-prone environment had to be addressed using a technological solution.
Thus, in 1992, construction of the "Outer Underground Discharge Channel" was launched. The project was completed in June 2006 and, voilà, no floods in the area anymore.
To describe the way the flood protection system works very briefly: five collection silos collect the surplus water via a 6.3km long central tunnel from the minor rivers. Each of the containment silos is about 70m high and 30m wide and would thus be able to easily contain the Space Shuttle or the Statue of Liberty - as the booklet of the Discharge Channel proclaims. The water is then shot through the 10m wide underground water tunnel running 50m below Highway 16 (a major thoroughfare) towards the surge tank facility in Kasukabe.
Water contaiment silo from above, Kasukabe Underground Flood Protection Tank (aka G-Cans), Saitama Prefecture
Pump station control room, Kasukabe Underground Flood Protection Tank (aka G-Cans), Saitama Prefecture
Release into Tokyo Bay
Once the huge rainfall is over and the situation reverts to normal, the stored water is pumped up into the Edogawa River for it to eventually be safely released into Tokyo Bay.
The flood protection system as such is certainly a great engineering feat and, indeed, engineers from all over the world have been intensely studying the system since it was inaugurated.
But why would anybody bother putting it on their Tokyo visiting agenda? The answer is that the underground surge tank is an incredible sight. An industrial cathedral of enormous proportions. The engineers designing it probably didn't have art on their mind when they drew their sketches but, nonetheless, they created one of the most elegant and beautiful underground spaces in the whole Tokyo Metropolitan Area.
The surge tank has featured extensively in both domestic and international media and thus attained a popularity which makes booking a spot on one of the guided tours a bit of a challenge.
Edogawa River near the tank facility
Booking A Tour
Tours take place every day of the week, and there are 7 tours per day. The frequency of tours, and the number of allowed participants per tour, were significantly increased in August 2018, so it is not as difficult to get a place on a tour as it used to be. However, it pays to book early, just in case.
The surge tank web site also informs you that you must bring serious footwear (no access permitted wearing sandals) and, if you are a foreigner, you must either speak Japanese reasonably well or bring someone who can interpret for you.
Displays in the RyuQ-Kan, Metropolitan Area Outer Underground Discharge Channel, Kasukabe
The tours are in Japanese and if suddenly flood water surges in, you must be able to understand the emergency directions of the tour guides.
Once you have successfully booked your spot on one of the tours, be sure to arrive at the 2nd floor of the main pump building, the Ryū-Q Kan, about half an hour before the scheduled starting time. The Ryu-Q Kan is the museum of the facility, and features scale models and an 8-minute video (with English subtitles) that briefly explains the history and workings of the Metropolitan Area Outer Underground Discharge Channel. However, the best resource is the very comprehensive and well-written 11-page English-language pamphlet handed out when you check in.
The tour itself starts with someone explaining much the same background information, but in Japanese, for the whole group. The tour group then leaves the Ryu-Q Kan and walks 3 minutes, past a soccer field that sits right on the top of the underground surge tank, to the entrance to underground cavern with the stairway down into it.
Scale model of pump gear mechanism at the Ryu-Q Kan.
The tank is about 22m meters deep. Various landings on the stairs down offer great views, but you are not supposed to take photos from there. Eventually, you arrive at the bottom of the tank.
When I went, the floor was still wet and plenty of mud covered the floor space between the columns. The last big rainfall had just been a few days before. The visitor area had, however, already been cleaned.
After listening to another talk about the tank and its details (the tank is 177m long, 78 meters wide, 18m high, with 59 pillars and each of those pillars is 7m long, 2m wide and weighs about 500 tons), you can eventually walk around on your own within the limited visitor area and try to find the best photo opportunities.
Pre-tour explanation at the RyuQ-Kan
The giant surge tank is definitely very impressive. But there is no way to see any of the other underground facilities of the huge flood protection system. It would certainly be great to be able to walk through one of the huge tunnels belonging to the system, and look at the giant pumps that suck the stored water from the tanks and discharge it into the Edogawa River, but you can experience them only through the video provided in the Ryu-Q Kan.
The tour is over once you climb back up the steps and return to the Ryu-Q Kan. The tour takes about 50 minutes in total.
Take a walk over to the Edogawa River. Interestingly, the river here here is not encased in a concrete bed like so many other Japanese rivers are, but is free to expand its size as needed. The land bordering it is farmland with hardly any buildings—just like in the times before the suburban sprawl set in.
Stairs down into the Kasukabe Underground Flood Protection Cavern.
Web Information
Visitor website of the Metropolitan Area Outer Underground Discharge Channel: http://www.ktr.mlit.go.jp/edogawa/gaikaku/index.html
The site has an English-language section with information about the surge tank and the booking requirements.
You can book tours in English via that English-language section. You can pay online by credit card. Be warned that the site is a little clunky in its organization, and that payment requires you to go back to the main menu and click a different "payment" button after you have completed the details of the booking.
Booking
You can book a visit anytime, but it is wise to do so as far in advance as possible.
Tours
Every day of the week, including on public holidays. There are 7 tours a day: 10am, 11am, 12 noon, 1pm, 2pm, 3pm, 4pm. Each tour takes 50 minutes, with a maximum of 50 people per tour. Requirements: Bring proper footwear. If you don't speak Japanese, bring someone who can (and who must of course be signed up as part of the tour). The tour costs 650 yen per person.
Please read the instructions given on the English-language visitor site carefully.
Access
Train: The closest train station is Minami Sakurai (南桜井駅) on the Tobu Urban Park Line (formerly Tobu Noda Line) from Omiya Station in Saitama. To get to Omiya Station take a shinkansen from Tokyo Station (25 minutes) or the Takasaki Line from Ueno Station (25 minutes).
Bus: The Aeon Mall Kasukabe Bus leaves from outside the North Exit of Minami-Sakurai Station. There are about two buses an hour between about 9am and 5pm (a little less on weekends/public holidays), and the current fare (October 2018) is 350 yen one way. Pay as you board. Takes cash only. (IC smartcards are not accepted). Also, there is no change dispenser, so have the right coins ready. The ride takes about 10 minutes.
By taxi: Take a taxi from the North Exit of Minami-Sakurai Station. Tell the driver "Ryu-Q Kan," or, if that doesn't work, "Hoh-swee-ro." Expect to pay a taxi fare of around 1,500 yen one-way.
On foot: Walking from the station takes about 30 minutes to the Metropolitan Area Outer Underground Discharge Channel. If the weather is good, it's a pleasant walk through farming country, and a great way to see up close how life is lived in rural Japan.
By car: Parking is available. Please note that driving in the northern suburbs of Tokyo tends to be very slow due to congestion and poorly coordinated traffic lights.
Visitors heading for the underground flood control cavern, Ryu-Q Kan in background
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Kasukabe Underground Flood Protection Tank (aka G-Cans) 首都圏外郭放水路, 春日部市
by Johannes Schonherr
The official English name for whole of the giant installation is the Metropolitan Area Outer Underground Discharge Channel. Located on the outskirts of Kasukabe City in Saitama Prefecture, it is a flood protection facility for eastern Saitama Prefecture and parts of north east Tokyo, namely, Adachi, Katsushika and Edogawa wards.
Kasukabe Underground Flood Protection Surge Tank, Saitama
Open to the public is only the cathedral-like underground surge tank next to the bed of the Edogawa River, right at the border to Chiba Prefecture, commonly known as the G-Cans.
It is an impressive sight indeed. That booking a visit can be a bit tricky only adds to its lure.
Background
But before I go into the details of a visit, I should provide a little background. Eastern Saitama Prefecture is located in the so-called Nakagawa Basin. It is low-lying land, below the level of the wide Edogawa River, and several small rivers, the Nakagawa being one of them, run through it.
The area has traditionally been very flood-prone, especially during the snow melt period in the mountains where the rivers originate and even more so as a result of the frequent typhoons that hit the area. Farmers often lost their harvests to the floods, but they were of little concern to the authorities.
From the 1960's on, however, the Tokyo Metropolitan Area began to extend into the Nakagawa Basin. By the 1980's, the farms had been almost completely replaced with suburban housing and industrial facilities. New train lines spread out and the real estate bubble of the late 1980's created a feverish housing market in the area; but little thought was given to the flood danger the prospective buyers faced.
Water containment silo seen from the surge tankKasukabe pump station and Ryu-Q Kan visitor center, Kasukabe Underground Flood Protection Tank (aka G-Cans), Saitama Prefecture
Flood Control
As a result, the area repeatedly became the victim of serious flooding, causing huge financial losses for a vital part of the economy of the Tokyo Metropolitan Area.
Something had to be done. The man-made problem of settling a huge population in a flood-prone environment had to be addressed using a technological solution.
Thus, in 1992, construction of the "Outer Underground Discharge Channel" was launched. The project was completed in June 2006 and, voilà, no floods in the area anymore.
To describe the way the flood protection system works very briefly: five collection silos collect the surplus water via a 6.3km long central tunnel from the minor rivers. Each of the containment silos is about 70m high and 30m wide and would thus be able to easily contain the Space Shuttle or the Statue of Liberty - as the booklet of the Discharge Channel proclaims. The water is then shot through the 10m wide underground water tunnel running 50m below Highway 16 (a major thoroughfare) towards the surge tank facility in Kasukabe.
Water contaiment silo from above, Kasukabe Underground Flood Protection Tank (aka G-Cans), Saitama Prefecture
Pump station control room, Kasukabe Underground Flood Protection Tank (aka G-Cans), Saitama Prefecture
Release into Tokyo Bay
Once the huge rainfall is over and the situation reverts to normal, the stored water is pumped up into the Edogawa River for it to eventually be safely released into Tokyo Bay.
The flood protection system as such is certainly a great engineering feat and, indeed, engineers from all over the world have been intensely studying the system since it was inaugurated.
But why would anybody bother putting it on their Tokyo visiting agenda? The answer is that the underground surge tank is an incredible sight. An industrial cathedral of enormous proportions. The engineers designing it probably didn't have art on their mind when they drew their sketches but, nonetheless, they created one of the most elegant and beautiful underground spaces in the whole Tokyo Metropolitan Area.
The surge tank has featured extensively in both domestic and international media and thus attained a popularity which makes booking a spot on one of the guided tours a bit of a challenge.
Edogawa River near the tank facility
Booking A Tour
Tours take place every day of the week, and there are 7 tours per day. The frequency of tours, and the number of allowed participants per tour, were significantly increased in August 2018, so it is not as difficult to get a place on a tour as it used to be. However, it pays to book early, just in case.
The surge tank web site also informs you that you must bring serious footwear (no access permitted wearing sandals) and, if you are a foreigner, you must either speak Japanese reasonably well or bring someone who can interpret for you.
Displays in the RyuQ-Kan, Metropolitan Area Outer Underground Discharge Channel, Kasukabe
The tours are in Japanese and if suddenly flood water surges in, you must be able to understand the emergency directions of the tour guides.
Once you have successfully booked your spot on one of the tours, be sure to arrive at the 2nd floor of the main pump building, the Ryū-Q Kan, about half an hour before the scheduled starting time. The Ryu-Q Kan is the museum of the facility, and features scale models and an 8-minute video (with English subtitles) that briefly explains the history and workings of the Metropolitan Area Outer Underground Discharge Channel. However, the best resource is the very comprehensive and well-written 11-page English-language pamphlet handed out when you check in.
The tour itself starts with someone explaining much the same background information, but in Japanese, for the whole group. The tour group then leaves the Ryu-Q Kan and walks 3 minutes, past a soccer field that sits right on the top of the underground surge tank, to the entrance to underground cavern with the stairway down into it.
Scale model of pump gear mechanism at the Ryu-Q Kan.
The tank is about 22 meters deep. Various landings on the stairs down offer great views, but you are not supposed to take photos from there. Eventually, you arrive at the bottom of the tank.
When I went, the floor was still wet and plenty of mud covered the floor space between the columns. The last big rainfall had just been a few days before. The visitor area had, however, already been cleaned.
After listening to another talk about the tank and its details (the tank is 177m long, 78 meters wide, 18m high, with 59 pillars and each of those pillars is 7m long, 2m wide and weighs about 500 tons), you can eventually walk around on your own within the limited visitor area and try to find the best photo opportunities.
Pre-tour explanation at the RyuQ-Kan
The giant surge tank is definitely very impressive. But there is no way to see any of the other underground facilities of the huge flood protection system. It would certainly be great to be able to walk through one of the huge tunnels belonging to the system, and look at the giant pumps that suck the stored water from the tanks and discharge it into the Edogawa River, but you can experience them only through the video provided in the Ryu-Q Kan.
The tour is over once you climb back up the steps and return to the Ryu-Q Kan. The tour takes about 50 minutes in total.
Take a walk over to the Edogawa River. Interestingly, the river here here is not encased in a concrete bed like so many other Japanese rivers are, but is free to expand its size as needed. The land bordering it is farmland with hardly any buildings—just like in the times before the suburban sprawl set in.
Stairs down into the Kasukabe Underground Flood Protection Cavern.
Web Information
Visitor website of the Metropolitan Area Outer Underground Discharge Channel: http://www.ktr.mlit.go.jp/edogawa/gaikaku/index.html
The site had an English-language section with information about the surge tank and the booking requirements. This seems to have stopped.
If you would like JapanVisitor to try and book a tour for you for a fee please contact us and provide your name, the number of visitors and your preferred and alternative dates.
Booking
You can book a visit anytime, but it is wise to do so as far in advance as possible.
Tours
Every day of the week, including on public holidays. There are 7 tours a day: 10am, 11am, 12 noon, 1pm, 2pm, 3pm, 4pm. Each tour takes 50 minutes, with a maximum of 50 people per tour. Requirements: Bring proper footwear. If you don't speak Japanese, bring someone who can (and who must of course be signed up as part of the tour). The tour costs 650 yen per person.
Access
Train: The closest train station is Minami Sakurai (南桜井駅) on the Tobu Urban Park Line (formerly Tobu Noda Line) from Omiya Station in Saitama. To get to Omiya Station take a shinkansen from Tokyo Station (25 minutes) or the Takasaki Line from Ueno Station (25 minutes).
Bus: The Aeon Mall Kasukabe Bus leaves from outside the North Exit of Minami-Sakurai Station. There are about two buses an hour between about 9am and 5pm (a little less on weekends/public holidays), and the current fare (October 2018) is 350 yen one way. Pay as you board. Takes cash only. (IC smartcards are not accepted). Also, there is no change dispenser, so have the right coins ready. The ride takes about 10 minutes.
By taxi: Take a taxi from the North Exit of Minami-Sakurai Station. Tell the driver "Ryu-Q Kan," or, if that doesn't work, "Hoh-swee-ro." Expect to pay a taxi fare of around 1,500 yen one-way.
On foot: Walking from the station takes about 30 minutes to the Metropolitan Area Outer Underground Discharge Channel. If the weather is good, it's a pleasant walk through farming country, and a great way to see up close how life is lived in rural Japan.
By car: Parking is available. Please note that driving in the northern suburbs of Tokyo tends to be very slow due to congestion and poorly coordinated traffic lights.
Visitors heading for the underground flood control cavern, Ryu-Q Kan in background
