
California Megaflood: Lessons from a Forgotten Catastrophe - youngerdryas
http://www.scientificamerican.com/article.cfm?id=atmospheric-rivers-california-megaflood-lessons-from-forgotten-catastrophe
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tomsaffell
If you're curious where these rivers are, take a look at a Map of California
Rivers that I made a few years ago[1]. Note that nearly the entire Sierra
Nevada range drains through the San Francisco Bay. Also note the small blue
globs along the rivers (e.g. Yuba) - these are reservoirs, which provide some
degree of flood protection, though probably not enough for the size of event
described.

    
    
      1. https://sites.google.com/site/calirivermap/

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jvanderwal
I had never heard of these "atmospheric rivers" prior to this article and
started doing a little reading.

"Atmospheric rivers are typically several thousand kilometers long and only a
few hundred kilometers wide, and a single one can carry a greater flux of
water than the Earth's largest river, the Amazon River." [1]

That's really impressive. I'm curious about their density and whether
airplanes have to avoid them, or if they're able to fly through.

[1] <http://en.wikipedia.org/wiki/Atmospheric_river>

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tgrass
Just to fill out the first four pages a little more:

[Edit] In the US [/Edit] your home and office are most likely already set
outside the floodwaters of the 100-year storm. New roads are typically
designed to convey floodwaters at no more than 1 foot deep for the same event.

Protecting a building that has a lifespan of less than 100 years against an
event with a probability of occurring between .005 to .002 (the 200-year to
500-year event) is a hard sell.

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HarryHirsch
> Protecting a building that has a lifespan of less than 100 years against an
> event with a probability of occurring between .005 to .002 (the 200-year to
> 500-year event) is a hard sell.

Only in America. The Delta Works in the Netherlands are designed for the
2000-year flood. This is the minimum - there are areas that are protected
against the 10000-year flood.

This makes sense. It is not normal that densely settled areas are flooded at
least once during the human lifespan.

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youngerdryas
>Only in America.

You don't seriously claim all of Europe is prepared for a 2000 year flood. I
doubt a lot of nations can afford it.

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HarryHirsch
South Holland is, and it has 4 million people living in it.

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youngerdryas
I was thinking more of Italy and its notorious construction fiascos.

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ChuckMcM
Wild, I've lived here nearly 30 years and had not heard about this flood. I
also found the concept of a concentrated stream of moist air (the the
"atmospheric river") to be an interesting, if somewhat sensationalized,
phenomena. Given the relative density of water vapor in these things they
should be pretty easy to spot by satellite.

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fencepost
Spotting it isn't really the problem - there's still nothing you can do about
it. Anything we could try to do would be like trying to stop a blizzard in
Chicago with hair dryers.

Even if you can't spot it you do have time to get out (it's not like all of
the rain happens in 24 hours), but the consequences of something like this
happening now in California would be enormous for the whole country just on
the basis of food. In the 1860's most food was (relatively) local, but these
days California actually produces something more than a quarter of the US food
supply (quick googling gives widely varying numbers without any attribution,
research is up to you), particularly fresh fruits and vegetables. Imagine the
Central Valley losing an entire year or more of growing season, probably with
the loss of a significant percentage of fruit & nut trees that take years to
replace. The ripple effect through the rest of the economy would be ugly.

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ChuckMcM
Well if someone could tell me that the big storm today was likely to last for
a month and by the end of it much of California would be a federal disaster
area, I'd consider driving over to Reno to spend some quality time on much
higher ground :-)

