Katrina was a "once a hundred year" storm. Likewise Sandy. Now Harvey is a "once in 500".

All within 12 years. I think we should stop measuring against data from a different global climate.

A "hundred year storm" doesn't mean we expect one per hundred years globally, but one per hundred years locally.

Even that is a little misleading (given how bad our intuition about statistics is). A '100 year flood' is flood that has a 1% chance of occurring in any given year (it's independent of what happened 1, 5, or 50 years ago).

Calling it a '100 year flood' makes people think 'oh, good, now we shouldn't have one of those for another ~100 years'. In reality, the odds of a flood of the same magnitude occurring next year are exactly the same as they were this year.

Grady (of the Practical Engineering YouTube channel) has a great video on this topic: https://www.youtube.com/watch?v=EACkiMRT0pc

(Grady is in the Austin area, so hopefully he hasn't too much 'practical' experience from this storm...)

The other thing to remember is a 5 year flood and a 100 year flood are often not very different in size.

I mean the same areas that flooded now flooded in Ike, Rita and Allison, so yea it does make sense. My family lived through each and I'm not sure why they stick where they are.

from what I can tell, it's healthier to live near the water, especially the ocean. so would you see also having an inland retreat as an appropriate set up?

When you buy a house in a town there's some chance you may spend the rest of your life there. Even if the risk really is 1/1000 per year, it's still N/1000 per house.

And the risk may be higher than 1/1000 per year given how much motivation is out there to understate the risk and say that nobody could have seen this coming.

It makes sense to rationalize a disaster as somebodys own fault, to get out of the guilt anyone should feel who is so anti-social he can abandon his community on a whime.