[url=pubs.usgs.gov/of/2010/1312]U.S. Geological Survey Open File Report 2110-1312[/url]

They model a storm which would cause more potential damage than the proverbial Big One (mag 7.8). Maybe I should take up boating, after alll.

They can predict anything they want on a computer. Ma Nature likes to give sneak punches.

"An ARkStorm raises serious questions about the ability of existing federal, state, and local disaster planning to handle a disaster of this magnitude."

Since 46 out of our 50 states are effectively broke, they probably wouldn't be able to provide more than a rowboat and bottle of water.

Sue

The interesting thing about their study is that there evidently have been storms of this magnitude or even larger throughout the last two thousand years. If their estimates of the damage are anywhere near correct, we would have a tough time, even in the best of economic cycles.

Been skimming the report a bit. The historical part is interesting. I had no idea that these megastorms have occurred in my home state every couple of centuries. When I first read the OP, I assumed the USGS must be talking about the East Coast or Midwest, not the West Coast. I mean, who thinks of the West Coast (California, in particular) when talking about catastrophic weather events?

Besides the loss of life, if the Central Valley of California ever flooded in a matter of days as they outline in the report, the agricultural loss and the loss of water, particularly to southern California, would be very painful. Most water districts could limp along for a while on stored water, but that will only last so long.

A massive earthquake could also cut us (southern California) off from our water supplies from Northern California, but I have a feeling that quake-damage may be quicker to repair than dealing with a massive flood. Repairs on quake damage could probably begin quickly, while just waiting for the floodwater to recede from an ARkstrom could take a very long time.

This ARkstorm report does make you look at the news from Queensland, Australia in a new light. That's another massive, massive flood event happening right before our eyes.

California should be the poster state for preparedness. Wildfires, mudslides, earthquakes, mega-rain -- being able to bug-out in a flash, shelter-in, camp in the backyard (earthquake damage), prudent to cover the bases.

I'd for darn sure want to be able to go it alone for more than 72 hours out there.

So when was the last mega-storm? Do they know?

The only mega storm in the historic record in the storm of 1861-62, when it rained in southern California for 28 straight days. A partial list of similar storms includes the year of 1029, 1418, and 1605. These earlier events are inferred on the basis of study of sediment deposits in the Santa Barbara Channel.

It's a long, detailed report. I have just started to read it.

The report says that in December 1861, severe storms lashed the area for 45 days. So, something you could actually go to a library and read old newspaper articles on.

Well, I'm not holding my breath waiting for the whole Central Valley to flood in an ARkstorm, but large-scale localized flooding could do a lot of damage, especially if it occurred in the Sacremento area. The city (our capital) itself could be underwater. And since this region is where the water heading for southern California originates, if flooding threatened the water supply heading south, I have read elsewhere that the aqueduct would be shut down.

A similar set of outcomes exists if the next major earthquake causes the extensive levee system in the Sacramento River Delta area to break down, causing a different kind of flooding and shut down of the California aqueduct.

1861-62. During the Civil War. Seems California is overdue.

Will try to read the report in the coming week.

We came close during the El Nino of 97-98, with rain most of February, which is usually our wettest month.

The Central Valley of CA they speak of is about 300+ miles long by ~50 mi wide (roughly, Chico to Bakersfield). In 1868 the CA population was somewhere around 500,000. Most of the whites at that time had immigrated to the area, so one might suspect that since they had survived a 1500-mile cross-country migration or trips around Cape Horn, they had at least some sense and survival instincts. Of the six million that live there now, I'm sure the ratio has changed.

That article might lead you to believe that the ARK storms of 1861-62 were the last atmospheric river storms that happened in CA, and they weren't. I was in one in SoCal in 1969, and there was another one in 1986 in NoCal. Marty Ralph, an atmospheric scientist of NOAA said that the two of them together would be the flooding equivalent of the 1906 San Francisco earthquake (about a magnitude of 8).

Maybe these weren't as serious as the earlier ones, but they certainly did a lot of damage.

Like other storms I've noticed, it followed a year with a disastrous fire. The Canyon Fire of 1968 burned over 20,000 acres of the mountains and foothills, fanned by the infamous hot, drying Santa Ana winds.

The first storm (January) produced 10 days of heavy rain, and then two days that produced 30" of rain, saturating the soil. The next storm hit in February and the whole area was overflowing with water. But I faintly remember rather constant rain, and that someone said it had rained every day for 45 or 48 days at one point, and my boss made a joke about Noah being luckier.

My boss had the fires right down to the block wall of his hillside home, so the hills above were mostly bare. Many of the usually-dry riverbeds (not concrete 'flood control channels') had bottlenecks where large metal grates had been installed with concrete. The home-building had been progressing up the hills, and many of the people who lived beside these channels used them as handy dumping areas. The debris washed downward and backed up behind the grates in the first storm. The water backed up behind the debris 'plugs' during the second storm. But the grates weren't meant to take that much pressure, and a little after 6 a.m. one morning, they started giving way.

One of our clients was waiting in the parking lot of the vet clinic where I worked. She was wearing a bathrobe, her kids in their pajamas. She said she had just seen her husband off to work when their St. Bernard started whining and scratching at the back door. She opened the door, but he wouldn't go out, just listened, very agitated. She stepped out with her coffee cup to see if there was a raccoon in the garbage can again, and saw an 8-ft wave of mud, boulders, bushes, trees and other debris slowly rolling out of the little canyon behind them. She grabbed the kids out of their beds and ran for the Jeep, jumped in with the dog, and took off down the hill. She said all she could think to do to warn the neighbors was to keep her hand on the horn all the way down.

Above the old Monrovia Nursery, another channel of water and mud had broken loose, rolling right down the street and through the bus stop where, 20 minutes later, people would have been collecting. The mud was about three feet deep, with boulders, fence posts and barbed wire, and a dead horse mixed in the mess.

My boss said the mud rolled down to his house off the bare slopes like pudding. It flowed until it hit the block wall, then found the edge and went down the driveway and surrounded the front and side of his attached garage. It flowed down to his neighbor's home (no wall) and slowly filled up the front patio, rising four feet up the face of his sliding glass door (it didn't break, but it sure did leak!). My boss's friend heard and arrived with two sons and a backhoe sort of thing with a big scoop on the front. The three men kept that backhoe running up and down the street 24 hrs a day for a couple of days (it continued to rain), saving his home and those of his few immediate neighbors. The water seeped out of the mud and filled his garage and two cars halfway up the doors with muddy, stinky water.

Someone's home had a six-foot boulder roll right through it, followed by mud and debris. Another photo showed the roof of a home, all that could be seen, the rest buried in mud to the eaves.

I don't know if Glendora was the hardest hit, or it just seemed so because I was working there and exposed to so many horror stories, but the National Geographic magazine, Oct. 1969, showed photos of the flooding and damaged homes. Over 100 people died.

Computer mockups can't touch the real thing.

Sue