How Do You Keep a Subway from Flooding in the Age of Rising Seas? (2019) | Hacker News Reader

How Do You Keep a Subway from Flooding in the Age of Rising Seas? (2019)

atlasobscura.com

84 pointsalanwong48 comments

I places in Asia that have monsoon weather one typically walks UP a few steps before going down into a subway station (China/Taiwan/Hong Kong/etc)- for example this MTR entrance in Hong Kong:

https://goo.gl/maps/MeiQU9HAKo5NgFAKA

This is a great solution to short term small floods, but wont protect you against longer term, or waist deep+ street flooding like we saw in Henan last week.

I’ve lived in Hong Kong for close to 10 years, and I never even thought about why almost every MTR entrance has a couple of steps up, only to go back down.

With something like this: https://commons.wikimedia.org/wiki/File:Exit_A,_Sino-Singapo... the intention is even clearer.

Yeah, thanks, I was actually looking for a pic of my favourite Shenzhen Science Museum entrance that has maybe 6 steps (and is a real pain to drag a suitcase up)

I noticed this in Chengdu and Taipei and wondered a few times, why go up just to go down. Thanks for explaining this!

Warsaw (Poland) uses the bulkheads which were designed originally during the cold war era to provide an atomic shelter for the civilians. Fortunately, they weren't ever used for the original purpose, but they are now used as a prevention during the storms.

- Original article in Polish: https://www.komputerswiat.pl/artykuly/redakcyjne/grodzie-prz...

- Just the video showing the partition: https://streamable.com/390cxk

Do they close off the whole subway system?

the whole point is that they only need to shut off the stations which are at risk of flooding

PS. I think only the stations build as the first phase of the first line (planned in the '70s-'80s and finished mid '90s) have this feature.

The Zhengzhou metro, one which got flooded, has blast doors in, and in between stations like most metros in the Bloc.

The anger now is because despite millions spent on those blast doors, they were simply not activated. The shift chief of the metro was too afraid to stop the metro.

The same for its very powerful flood defence pumps.

Reminds me of a documentary on the flood gates at the Port of Rotterdam. They are operated automatically, humans cannot trigger them (if memory serves well). Reasoning was, that operators live nearby and might tend to close them too soon and too often. Now you have to trust the system to have a proper balance between keeping the port open and protecting communities. Up to now the Rotterdam system seems to work reasonably well so.

And nobody needs to be worried about being fired for closing them 'for nothing'.

Exactly.

Do you have a source for that please?

I don't have a source for their statement specific to the doors, but here are some videos that capture how horrific events are unfolding in China the last few days. [1] I suspect finding documented sources of mishaps will be tricky as they will likely be moderated [2] once found.

[1] - https://www.youtube.com/channel/UCT2kPBcD6tXn8TP_aV7BmgA/vid...

[2] - https://news.ycombinator.com/item?id=27949726

Newer systems being built in Asia are avoiding subways/underground systems and preferring elevated systems. In fact during a major flood, the elevated railway was pretty much the only servicing transporting system in effect.

Because they trade ugly surface volume occupation for being much cheaper. Flood resistance is a side-effect.

for someone who loves trains, above ground rails are not ugly

The trains aren't ugly, the concrete infrastructure is. (Note that elevated trains in the US often look much nicer because they use steel structures, something that isn't being built today).

Roads are ugly too compared to a meadow. I'd rather have cars underground and human-powered vehicles and pedestrian only areas instead of roads.

On the other hand, in case of typhoon elevated lines often stop, unlike underground ones if there is no risk of flooding.

Not only subways, but when I was in Vietnam, a lot of the new highways around HCMC/Mekong Delta were all elevated for their entire length despite the landscape being flat. I assume to completely eliminate any flooding issues.

Which ones do you have in mind? All new lines in Shanghai are underground and so in a few other Chinese cities.

Hanoi's lines under construction are all elevated.

Bangcok?

> Sandy had made a mockery of the largest subway system in the world

Is the New York subway really the largest subway in the world? I thought that trophy went to subways in Tokyo or Seoul.

It depends how you measure it.

NYC has the most stations, 424.

Shanghai has the most track, 743 km, and the most annual riders, 2834.69m.

A quick Google says the Tokyo metro moves over 3.3 billion a year.

Perhaps that number is for "rides" and not "people".

Same type of number as the one given for Shanghai, I doubt that subway system moves 2x the population of China every year worth of unique individuals.

It depends on who you ask.

Ask a New Yorker, and the NYC subway is the greatest in the world (oh and PATH is not part of the subway system, cuz it's not MTA and goes to New Jersey).

Also, NYC itself is the greatest city on the world. ;-)

If I were to be the one deciding how to measure this, the “biggest” subway would be the one that moves the most people per day.

For me, complexity would have to be a factor.

A single ring line would in my view count as smaller than a more traditional "flared out" system, assuming they moved the same amount of passengers.

Maybe a complexity factor based on number of distinct tunnels multiplied by number of riders? Hmmm, metrics are hard...

Nah, breadth and depth

dont forget width!

Not sure about biggest but I will say NY subway is far more complex than Tokyo's and I'm a native English speaker and speak no Japanese.

Getting to the correct train in Tokyo was far easier, likely because there was less rerouting than what seems like perpetual issues in NY's subway due to aging infrastructure.

I’d echo this sentiment. I’ve spent a good amount of time in Tokyo (I don’t speak Japanese either, beyond simple “I am lost” and “where is the toilet” phrases), and for whatever reason I do find Tokyo’s trains easier to handle than New York’s. I can get around New York on my own without a map but that’s just because of brute force memorization and getting off at the wrong stop enough times.

Also NY's is the only system I've seen that has fast and slow trains on the same line. Definitely complicates things!

How will this hold up in 12 years?

https://www.nasa.gov/feature/jpl/study-projects-a-surge-in-c...

https://tidesandcurrents.noaa.gov/sltrends/sltrends_station....

110 years of 2.5mm per year. Something tells me the study you're referring to is wrong.

The NASA study is about flooding at high tide, not just the mean sea level. If you look closely at the graph in your source, you'll notice that the "monthly mean sea level with the average seasonal cycle removed" curve has a lot of variance. Now add monthly and seasonal cycles back in...

Maybe we will need to take the name a bit more literally :)

We can't change the past so have decades to centuries of climate change to handle, but we can do a lot more to stop future contributions to climate change.

The biggest effect anyone can have, beyond fewer kids, less meat, and flying less, is learning to lead others, which multiplies our effects. Of course, to lead others we have to lead ourselves first, which means fewer kids, less meat, flying less, and all those, as means to the end of leading others, especially CEOs and elected officials.

Meanwhile CCP going to extreme measures to reverse their one child policy. Last week, banning tutoring to decrease the cost of raising a child.

I thought the walls were the major variable and relatedly how well the earth blocks water in addition to well the local presence. The cost of any street opening subway is needing some pumping as even if you have over-awnings gravity brings rainwater down and it is rare that a city large enough a subway makes sense is away from bodies of water.

I assume more higher up "subways" will happen sooner or later and the underground approach will be used much less.

I wouldn't count on it. Skytrain's [0] been a thing for a couple decades now, but hasn't been emulated everywhere.

[0] https://en.wikipedia.org/wiki/SkyTrain_(Vancouver)

Good job

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