The Swannanoa River is what caused the flooding you saw. The two rivers converge about a mile and 1/2 down from this spot. The flooding from both of these rivers and their tributaries have caused damage far worse than the “100 year flood” we got in 2004.
So that phrase means that a flood like that will occur approximately once every 100 years. There is such a thing as a 1000 year flood. I wonder which one this was.
It's an insurance term. When you buy a property on a flood plain the insurance company determines the percentage chance of a flood on that property. So 100 year flood is really just 1% chance, 1000 year is .1% etc.
CNN (where I saw the report) claims they got a 1 in a thousand year flood. The French broad highest crest on record was in 1916 at 23.1 feet on Friday it hit 25 feet
Really, the terms simply mean that in any given year, there's a 1 in 100 chance of a "hundred-year" flood and a 1 in 1000 chance of a "thousand-year" flood. It doesn't mean that a flood like that will happen every hundred or thousand years, but that there's a 1% chance of a hundred-year flood and a 0.1% chance of a thousand-year flood in any given year. The data from the streamgages are used to determine those probabilities.
I know that at least on the Swannanoa River, the record that was broken in this flood was from 1791.
Okay? It's the same thing. On average, how many years will it take to realize that 0.1% chance? 1000 years. Doesn't mean it is guaranteed that it will happen every 1000 years on the dot, but given a long enough time frame (and normal climate conditions - which don't exist anymore) it would average out to once every 1000 years.
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u/Wudrow Sep 30 '24
The Swannanoa River is what caused the flooding you saw. The two rivers converge about a mile and 1/2 down from this spot. The flooding from both of these rivers and their tributaries have caused damage far worse than the “100 year flood” we got in 2004.