Tokyo combats flood threats with second mammoth reservoir

http://www.japantimes.co.jp/life/2014/08/17/environment/tokyo-combats-flood-threats-second-mammoth-reservoir/#.U_Pzq_mSyqm

by thret • 12 years ago

43 24 12 years ago

japantimes.co.jp

TheLoneWolfling• 12 years ago

"Sorry, but your browser needs Javascript to use this site. "

No thank you.

userbinator2• 12 years ago

Agree with the sentiment but I can read the article with JS off.

okasaki• 12 years ago

Are you sure? I just get that message and no article.

joezydeco• 12 years ago

Chicago, for example, stores water and sewage in a nearby quarry during periods of heavy rain.

Um, it's more than a quarry. Chicago is 3/4 through a sixty year project to install more than 100 miles of underground tunnels and reservoirs which will hold 66 million cubic meters of water when finished in 2029 (or thereabouts). The quarry is a temporary reservoir.

http://en.wikipedia.org/wiki/Tunnel_and_Reservoir_Plan

userbinator2• 12 years ago

the 3.3-km-long tunnel-shaped reservoir, which is 7.5 km in diameter

That seems absurdly large. Then again, I suppose they want to avoid the question "what happens when it overflows?"

jws• 12 years ago

I believe it is 7.5 meters in diameter.

vacri• 12 years ago

I think it's a typo as well - it had me scratching my head at how something can be less than half as long as it's own diameter.

lotsofmangos• 12 years ago

The picture in the article would seem to be a 7.5m tunnel, if the person in the picture is about 1.8m high.

But this is Japan, so I'm going for 7.5km and the person is actually a 1.8km high Super Dimensional Fortress.

wodenokoto• 12 years ago

11 CM of rain an hour? 7.5 km in diameter? Those looks like typos to me.

kijin3• 12 years ago

7.5km diameter is definitely a typo, it's supposed to be 7.5m.

11cm of rain per hour is not a typo. The Pacific Ocean contains more water than the rest of the oceans combined, and it can dump it wherever the hell it wants. East and Southeast Asia are particularly vulnerable because the trade winds blow hot moisture toward Asia (and away from the Americas). During the monsoon or when a big typhoon hits, some locations can get more than 10cm of rain per hour, although it's usually localized to a small area and only lasts a few hours.

Just a couple of weeks ago, a typhoon hit Jeju island in South Korea and dumped 1 meter of rain in 24 hours. That would be more than an entire year's worth of rain in most parts of Europe and North America, and would have been catastrophic if not for the highly porous volcanic geology of Jeju. The current record for South Korea is around 15cm per hour. Since Japan gets more typhoons than we do, I wouldn't be surprised if their record was even higher.

cdr• 12 years ago

Localized precipitation can be unbelievable when a front stalls over an area, no major event like a typhoon / hurricane even required. The September 2013 floods in the front range of Colorado caused by a stalled front topped out at 9.6mm/hour on the worst day, with 430 mm total in 6 days - just under the average annual precipitation.

blueskin_3• 12 years ago

7.5km is clearly a typo.

11cm of rain isn't - this isn't that uncommon in extreme storm conditions.

chiph• 12 years ago

That's 4.3" of rain an hour. More than most Atlantic hurricanes, but not unknown for a Pacific typhoon.

Put me down as another person unimpressed with it's capacity - for a city the size of Tokyo, I expected it to be much larger. Perhaps it's only for one or two of the special wards? It's certainly a beautiful looking tunnel. But I can't help but wonder if they spent too much money/time on perfecting it.

blueskin_3• 12 years ago

There are a few similar tunnels to this in the UK, including one around where I live. It's an interesting method, and probably one a lot of the US could benefit from too.

shubb• 12 years ago

This £4.2bn scheme for instance: http://en.wikipedia.org/wiki/Thames_Tideway_Scheme

However, following the 2008 crisis, the government followed a strategy of immediate spending reduction (as opposed to US stimulus spend).

While mega projects such as this were still funded, the budget for environmental management was reduced by ~30% accounting for inflation. This impacted river and drainage channel maintenance, greatly increasing damage inevitable from bad weather.

The cost of the 2012 floods post cuts was £1bn, compared to a cost of 0.5bn from worse weather before the cuts in 2009 (similar rainfall accompanied by strong winds as well).This is about 30% more than the total saving from budget cuts.

The interesting thing is, I have not yet seen anyone in the press draw a connection. The locals know, that the floods rose from ditches and rivers that were not dredged. I've not seen the broader picture mentioned in the UK press once.

Maybe no one cares, because drainage is boring, and doesn't do anything when it isn't desperately needed. There are a lot of things like that.

qwerta2• 12 years ago

will be able to hold 135,000 cu. meters of water, enough to fill 54 Olympic-size swimming pools.

It must be hard to build it in middle of metropolis, but this is hardly 'mammoth'.

wisty• 12 years ago

Once you're talking volume, things start scaling cubicly. It's not intuitive to most people that a cubic meter of water weights a ton. It's certainly not intuitive how to compare say, the Hoover Dam to a 7.5km long (but skinny) reservoir.

This massive reservoir could be about 50 by 50 by 50 meters. Or 10 meters deep, and 120 meters square. Which is in a lot of water, in a sense.

But compared to the Hoover Dam, which is 2,600,000 cu of concrete (and about about 300 million times the capacity of the Japanese reservoir, if you're including Lake Mead) it's not very big.

Note - I might have made a huge mistake somewhere here. It's hard to tell when you start cubing things, because intuition starts breaking down.

qwerta2• 12 years ago

I was comparing it to other water reservoirs (Hoover Dam for example). 135,000 cu. meters is a droplet, small villages have larger reservoirs.

adventured• 12 years ago

I wonder if anyone has data on Japan's typhoon history. How many have hit the country per year the past century (I've been unable to locate such data). In regards to this:

"Tokyo is becoming increasingly reliant on this unique-to-Japan solution as more typhoons hit the country each year"

as the US has seen no increase in hurricanes, and the last decade in particular has been remarkably lacking in hurricanes.

Tokyo combats flood threats with second mammoth reservoir

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