The 100 Year Flood Is Not What You Think It Is (Maybe)

What people said

Balgair · 2019-05 · Recommendation

It's not human action that would worry me, it's nature. Freezing cycles could easily erode a pool in a few decades and make micro-cracks that fester unnoticed for years. Rust is an ever present issue for re-inforced concrete and is the cause of countless civil engineering disasters. Practical Engineering on Youtube is a great overview of the issues we humans have with water: [LINK] Of interest here are these videos: [LINK] [LINK] [VIDEO]

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JshWright · 2017-08 · Recommendation

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

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lsaferite · 2025-10 · Reference

Just for clarity, you're claiming that there's data to support that 10-year flood plain areas should be marked as having a 100% chance of having a flood every year and you have enough data to say a 100-year flood plain should be reclassified as a 10-year flood plain? I ask this because those numbers are shorthand for event probabilities given (flawed) observation data over large time-frames. Argue all you want about climate change moving these number due to rising sea levels. I agree it's happening. That being said, hyperbolic assertions such as this don't help. The reality is that our flood plain designations are very flawed, but they are the only current metric we have to assess some of these risks. Every location that receives precipitation or is near water has some risk of flooding and that risk of flooding may be hidden. The whole state of Florida is low elevation. Something like 1/3 of it is very low elevation and subject to sea-level rise causing catastrophic changes in coastline. But the other 2/3 of Florida is something like 100ft (30m) above sea level. The other issue with Florida is that it's the flattest state in the US. That flatness contributes to flooding being difficult to properly predict. > Dont buy houses in flood planes. I'd just like to call out this hard-line assertion as well. Have you looked at a flood plain map? They have hard borders of zones. Those zones are calling out that event probability. If I buy a house 10 ft outside that zone, do you think m

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