Houston is experiencing its third ‘500-year’ flood in 3 years • Hacker News Board

Re: Houston is experiencing its third ‘500-year’ flood in 3 years

#71

Post by pixl97 » Tue, Aug 29, 2017, 10:22 PM UTC

TallGuyShort wrote: post #38

pixl97 wrote: post #33

Earlier quoted context omitted.

>. It would seem the probably has gone up due to climate change That probably has a small reason to do with the increase, but your next line highlights the issue. > or that we're noticing the floods more now because there's more damage to be caused to more things that have been built up No, not exactly. The more stuff you build, the faster water runs off. Unincorporated land has a pretty high water slowing capability…

I actually hadn't thought about that aspect at all. I was thinking more along the lines of 'more development -> more stuff to get destroyed', but that's kinda backwards anyway because a flood would probably wipe out a bigger portion of infrastructure hundreds of years ago than it does now. But faster run-off sounds like a good thing to prevent the flood - are you saying that more development upstream means more flood…

Yes, lower latency is a pretty good example.

Also people tend to drain marshes and any other shallow stagnant waterways to avoid mosquitoes having breeding places. It can save us from terrible diseases, but it can make flooding worse.

Re: Houston is experiencing its third ‘500-year’ flood in 3 years

#72

Post by imnotlost » Tue, Aug 29, 2017, 10:32 PM UTC

rsync wrote: post #37

devy wrote: post #5

Fort Bend County Judge Robert Hebert stated that Hurricane Harvey is more like a 800-year event, as quoted from the statement from Monday, reported by the same newspaper WaPo[1] [1]: https://www.washingtonpost.com/news/post-nation/wp/2017/08/2...

"Fort Bend County Judge Robert Hebert stated that Hurricane Harvey is more like a 800-year event" 500 years, 800 years ... even 1000 years - none of those are timetables that planning for city ^H^H^H^H region the size of Houston should be operating on. A city that large, that populous and with that much economic activity that is crucial to the world should be using risk models to 10k year events. This is not unpreced…

Which American city, if any, plans for anything close to that time scale?

Seems like every city, county, state, etc. screw up planning on less than human time scales - pensions and infrastructure maintenance for instance.

Re: Houston is experiencing its third ‘500-year’ flood in 3 years

#73

Post by epitomix » Tue, Aug 29, 2017, 10:41 PM UTC

bkohlmann wrote: post #2

While the article obliquely makes reference to this, I wonder if this is somewhat similar to the "birthday" problem in statistics. Any given person has ~1 in 365 chance of being born on a particular day. Yet, if you have 30 people in a room, there is a greater than 50 percent chance that at least one PAIR has the same birthday. Given the hundreds of cities (thousands?) in the US that may be affected by a flood, it's…

I think that this statistic only makes sense if it is specific to the location. Otherwise, it is useless for planning purposes. If it is specific to the location then the birthday paradox does not apply.

Interesting note, this is Houstons third 500-year flood in three years [1].

[1] -https://www.washingtonpost.com/news/wonk/wp/2017/08/29/houst...

Re: Houston is experiencing its third ‘500-year’ flood in 3 years

#74

Post by oso2k » Tue, Aug 29, 2017, 10:42 PM UTC

bkohlmann wrote: post #2

While the article obliquely makes reference to this, I wonder if this is somewhat similar to the "birthday" problem in statistics. Any given person has ~1 in 365 chance of being born on a particular day. Yet, if you have 30 people in a room, there is a greater than 50 percent chance that at least one PAIR has the same birthday. Given the hundreds of cities (thousands?) in the US that may be affected by a flood, it's…

The "Birthday Problem" has a simple explanation. Something like nearly 45% of people are born in the Summer months. Ensure that you get people of different ages and your chances of finding someone with similar/same birthday goes up enormously.

Re: Houston is experiencing its third ‘500-year’ flood in 3 years

#75

Post by brewdad » Tue, Aug 29, 2017, 10:49 PM UTC

oso2k wrote: post #74

bkohlmann wrote: post #2

While the article obliquely makes reference to this, I wonder if this is somewhat similar to the "birthday" problem in statistics. Any given person has ~1 in 365 chance of being born on a particular day. Yet, if you have 30 people in a room, there is a greater than 50 percent chance that at least one PAIR has the same birthday. Given the hundreds of cities (thousands?) in the US that may be affected by a flood, it's…

The "Birthday Problem" has a simple explanation. Something like nearly 45% of people are born in the Summer months. Ensure that you get people of different ages and your chances of finding someone with similar/same birthday goes up enormously.

Is this true? Which months are considered "summer"? Northern Hemisphere or Southern or both? This can easily turn into a "40% of sick days are on Monday or Friday" type fallacy.

Re: Houston is experiencing its third ‘500-year’ flood in 3 years

#76

Post by pmalynin » Tue, Aug 29, 2017, 10:52 PM UTC

oso2k wrote: post #74

bkohlmann wrote: post #2

While the article obliquely makes reference to this, I wonder if this is somewhat similar to the "birthday" problem in statistics. Any given person has ~1 in 365 chance of being born on a particular day. Yet, if you have 30 people in a room, there is a greater than 50 percent chance that at least one PAIR has the same birthday. Given the hundreds of cities (thousands?) in the US that may be affected by a flood, it's…

The "Birthday Problem" has a simple explanation. Something like nearly 45% of people are born in the Summer months. Ensure that you get people of different ages and your chances of finding someone with similar/same birthday goes up enormously.

Thats....not how that works. At all.

Re: Houston is experiencing its third ‘500-year’ flood in 3 years

#77

Post by mbroncano » Tue, Aug 29, 2017, 10:52 PM UTC

The elephant in the room has been mentioned somewhere else these days: severe lack of planning and crumbling infrastructures.

Remarkably how ne of the few non-partisan issues on the table goes under the radar time and time again. Tongue in cheek, we might think only polemic issue get the attention of the public.

There is also the notion of national pride. We built our infrastructural base earlier than pretty much anyone else in the world, but we don't invest consistently on them anymore. Today our roads, dams etc. pale in comparison with any western country's but it seems like it's an affront to our national pride to acknowledge that.

Houston is ill prepared to face any kind of emergency like this one, and only the bravery and tenacity of the people is preventing a humanitarian disaster in the scale that would keep us awake at night. That's not the American way: planning, preparing and executing is. The sooner we start taking this leap the better.

Re: Houston is experiencing its third ‘500-year’ flood in 3 years

#78

Post by 21 » Tue, Aug 29, 2017, 10:53 PM UTC

danielvf wrote: post #3

Cue discussion on the works of Tabeb, and what a horrible job humans do at predicting the frequency of rare events.

He just tweeted about it:

"When people talk about 500 y floods or 100 year rain, they are klueless abt tail distribution. The empirical distribution is NOT empirical!"

(and a picture with math equations)

https://twitter.com/nntaleb/status/902632121407299585

Re: Houston is experiencing its third ‘500-year’ flood in 3 years

#79

Post by ars » Tue, Aug 29, 2017, 10:53 PM UTC

blondie9x wrote: post #61

The fundamental takeaway from this article is about half way down. Major flood events are occurint more frequently. What was once likely to hit a city every 500 years is happening to more cities on a planetary scale more frequently.

I know it's easy to blame climate change for anything and everything, but that's simply incorrect.

The actual takeaway is that our data is wrong, these floods occur more often than we thought. With only 150 years of good data, it's impossible to calculate "500 year" events accurately. You would need around 5,000 years of data to do that, and we don't have it.

So we ended up significantly underestimating how often these events occur.

Re: Houston is experiencing its third ‘500-year’ flood in 3 years

#80

Post by bitwize » Tue, Aug 29, 2017, 10:54 PM UTC

oso2k wrote: post #74

bkohlmann wrote: post #2

While the article obliquely makes reference to this, I wonder if this is somewhat similar to the "birthday" problem in statistics. Any given person has ~1 in 365 chance of being born on a particular day. Yet, if you have 30 people in a room, there is a greater than 50 percent chance that at least one PAIR has the same birthday. Given the hundreds of cities (thousands?) in the US that may be affected by a flood, it's…

The "Birthday Problem" has a simple explanation. Something like nearly 45% of people are born in the Summer months. Ensure that you get people of different ages and your chances of finding someone with similar/same birthday goes up enormously.

The birthday problem still exists even assuming that everyone has an equal chance of being born on any day of the year. It's a phenomenon of the statistical likelihood that given a large enough group of people, the likelihood that any two will have the same birthday goes to almost certainty very rapidly.