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.
Houston is experiencing its third ‘500-year’ flood in 3 years
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Re: Houston is experiencing its third ‘500-year’ flood in 3 years
#62While 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…
Birthday paradox relies on non-independent events. I'd assume floods should be relatively independent between different cities, meaning that the number of 500-year flood events in the U.S. would follow a binomial distribution ( https://en.wikipedia.org/wiki/Binomial_distribution ). p = 1/500 years = 0.002 For 100 cities, the probability of at least one city having a 500-year flood is 18.14%. For a 3-year run: p = (1/…
How does the birthday paradox rely on non-independent events?
Re: Houston is experiencing its third ‘500-year’ flood in 3 years
#63Howdy! I work in cleantech, and I guess it's that time again for a what-can-you-do-about-it post :) To start, here's my favorite climate change joke: "They say we won't act until it's too late... Luckily, it's too late!" ==So what can you do about it?== The biggest thing that is most relevant to the HN audience is that you can work at a new energy technology company! Our industries are out of the R&D stage and are cu…
The alternative approach to working directly towards solving the problem is to work at a mature tech company with higher pay, and donate 10% or more of your income every year to a non-profit like the Natural Resources Defense Council.
Our roadblocks in cleantech aren't money, but logistics. The tech is economical, and we just need to roll it out as fast as possible.
So while contributing your money is good, contributing your talent is an order of magnitude better.
Re: Houston is experiencing its third ‘500-year’ flood in 3 years
#64Earlier quoted context omitted.
The alternative approach to working directly towards solving the problem is to work at a mature tech company with higher pay, and donate 10% or more of your income every year to a non-profit like the Natural Resources Defense Council.
Work where your skills have the highest impact. Sometimes it translates into labor -> dollars.
Unless you're a lobbyist I feel like donations to lobbying organization would have the greatest impact. Many politicians are bought for what is comparetively a small amount of money compared to the impact they have.
Re: Houston is experiencing its third ‘500-year’ flood in 3 years
#65Earlier quoted context omitted.
"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…
Sounds like the city fell asleep at the wheel, or rolled the dice and didn't want to pay for proper drainage. Now the citizens get to pay. Sounds like the Judge is preparing the country for the fact that nothing will still be done about it.
The City of Houston, which votes Democrat, has actually done a reasonable job of upgrading its infrastructure over the years. For example all roads built/upgraded since the 90s are designed to act as drainage systems.
The problem is that Houston is a big city and its population has been rising very quickly, and the city government's efforts have been insufficient. And since the Texas state government is dominated by gotta-keep-government-small-and-taxes-low Republicans, Houston has received almost no assistance from the state in this regard. We are seeing the results of that today.
Re: Houston is experiencing its third ‘500-year’ flood in 3 years
#66While 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…
Having lived in Houston, this isn't a measure of the flood but a measure of how terrible the infrastructure is. They have terrible flood management systems but are "rated" to handle everything but a "100" year flood... yet Houston gets 100 year floods every year- multiple ones- and has for 40 years.
It's a scam involving the ratings much like the mooody's ratings scam of the last decade IMNSHO
Re: Houston is experiencing its third ‘500-year’ flood in 3 years
#67Earlier quoted context omitted.
more likely their model is wrong. it reminds me of fukushima: https://ml.berkeley.edu/blog/2017/07/13/tutorial-4/
Their model is wrong, but it's because it assumes climate is stationary. Climatologists are actively debating what the models should look like when global warming is taken into account: https://i.imgur.com/HLxUBim.png edit: not sure why I'm being downvoted. I can only assume the downvotes are political in nature, which is a shame.
That's not such a great reference...
Re: Houston is experiencing its third ‘500-year’ flood in 3 years
#68While 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…
How do you count "floods"? If there is one hurricane that causes floods in 3 cities, is that 1 flood, or 3?
If it's 1 - which is what I think is meant when saying "a 1 in XXX years flood" - then your comparison doesn't hold, because the number of floods isn't dependent on the number of cities, but on the distribution of cities on the land, and specifically in flood-prone areas.
Re: Houston is experiencing its third ‘500-year’ flood in 3 years
#69Earlier quoted context omitted.
The nomenclature is not the problem, the problem is making numerical estimates of low probability events based on just 150 years of data and a raft of modeling assumptions.
The problem is not making numerical estimates of low probability events or how such events are modeled: it's completely ignoring the statistical probability distributions of the model. All of the models are extremely "long tail" distributions and just about entirely ignoring the long tail. We shouldn't be referring to this as a low-probability flood but as a high sigma flood. ETA: Disclaimer: Day job includes rainfal…
I don't know much about the field, but I'm curious. How much are estimates based on normal distributions, and how much does the model consider other distributions?
As you say, I don't think we know much about the tail. More than ten inches of rain may be a once a year phenomenon, but that once a year event might be twenty or fifty inches?
Re: Houston is experiencing its third ‘500-year’ flood in 3 years
#70While 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 understand your argument, but you can't compare floods to the birthday problem. Unlike randomly-sampled people's birthdays, floods in US cities are not independent random variables. For instance, chances of 500-year floods in two Texas cities is not 1 out of 500*500 in a year. If they're geographically similar and physically close, it should be closer to 1 out of 500.
In 2 Texas cities, sure, but in every U.S. city? There are going to be several that end up getting a few 500-year floods... and several others that don't flood as expected in several 1000 years.