We're only beginning to understand the historic nature of Helene's flooding

I was supposed to be there Monday. I am flying out Friday instead. My family, obviously, doesn't have power and water yet. The best estimates they have are a month for water and power may come back in the next few days. I26 north I40 west are impassible and may be that way for months. Friends businesses are gone. It is a mess. I plan on doing the only thing that non-emergency people should do in things like this: drive my family out of there as soon as I arrive. Fewer people = fewer problems. As to what got us here? Bad things happen to well prepared places (Japan in 2011?) but having lived in truly well prepared places, I gotta argue that US infrastructure and planning isn't great compared to a lot of other countries (definitely better than some though). Infrastructure always pays for itself in the long term but we have so much short term, selfish, anti-science thinking that it is scary.

It was a bad disaster. I was scheduled to be there, but took a look at the NOAA rainfall map the night before and canceled my trip.

Calling it unthinkable is really overselling it though. Mountain towns and roads flood when it rains a lot. If you search past years google search results for Chimney Rock, it floods with 3" to 5" inches of rain. The town is just a few feet above water level - I've walked along the river.

Accumulated Cyclone Energy (ACE) https://tropical.atmos.colostate.edu/Realtime/

The figure in parentheses is ACE, averaged over 30 years up to and including September 30th: 77.8 (94.1)

There's more detail here, including a helpful chart: https://tropical.atmos.colostate.edu/Realtime/index.php?loc=...

EDIT: Interesting that Beryl had more ACE than Helene. I wonder if that figure will change as the effects from Helene are investigated further?

If you want to get a feel for what some of the rain people are talking about is like, see if you can find a model of rainfall intensity for your area. A good place to look is on the websites of your state government departments that have to deal with drainage and runoff.

For example here in Washington that would be the Department of Transportation. They need to be estimate how often a given area will get X inches of rain over Y minutes for a range of X and Y in order to figure out things like how big a culvert they need to put under a road. That information is in chapter 2 of their hydraulics manual which the public can download [1].

When someone mentions some ungodly amount of rain in a flood area, such as the 8" in 6 hours mentioned in another comment, you can take that rate (1.33"/hr) and then see how often you expect to see that rate where you are and for how long.

Doing that for my location, I expect to see 1.33"/hr every 2 years--but only for 8.5 minutes at a time. Every 5 years I can expect to see it for nearly 14 minutes. 18 minutes every 10 years. 25 minutes every 25 years. 32 minutes every 50 years. 38 minutes every 100 years.

Basically, then, if I think back over the last couple of years or so and remember the worst 8 minutes of rain I had, and then imagine it going on for 6 hours instead of just being an 8 minute pulse I'll have some idea of how much freaking rain that was.

Alternatively, I can see that I expect an interval of 6 hours with 0.19" of rain every 2 years, 0.24" every 5 years, 0.28" every 10 years, 0.33" every 25 years, 0.37" every 50 years, and 0.40" every 100 years.

So people who got 8" in 6 hours got 20 times as much rain as people where I live expect to see in 6 hours if they live here their entire life.

I'm curious what rates they get in those storms over shorter periods, such as 5 minutes. My tipping rain gauge takes about 100 ms to complete a tip, and it tips every 0.11", so if there was a spurt with intensity above 396"/hr it would not be able to keep up. Can those storms hit that over short intervals?

[1] https://wsdot.wa.gov/engineering-standards/all-manuals-and-s...

Insurance companies are undoubtedly moving out from servicing the areas. Voters continue to vote as if carbon dioxide and methane are not greenhouses gases that they emit. Such across-the-board denial of reality can have only one consequence: elimination.

We had flooding in Vermont on the same day in July as last summer’s flooding.

In a different deluge, one town had 8” of rain in six hours.

It would appear this is the new normal. Towns will have to be redesigned (some were built around rivers for power and transportation a long time ago).

Either i am having the biggest case of deja vu ever, or this post has time travelled.

I am certain i read this exact post and comments 2 or 3 days ago.

What did people expect when they built in floodplains with no flood insurance? My question is why taxpayers have to keep subsidizing the cleanup and rebuilding in these areas.