Atmospheric rivers drown California every 100 to 200 years

Atmospheric Rivers: an Amazon river in the Air

Atmospheric rivers occur around the world and can dump as much rainfall as hurricanes, carrying as much water as the Amazon river (Mackenzie). At any given moment there are about half a dozen atmospheric rivers above the earth. many drop their rain over the ocean before reaching land.

Most aren’t harmful — California gets up to half its precipitation this way. The problem comes when other weather systems cause these airborne rivers to stall out.  And climate change means that the air warms it will hold even more moisture, and atmospheric rivers even wetter, likely to form more often, last longer, and lead to more devasting floods in California (Dettinger).

ARkStorm: A $725 Billion Flood in California is expected

Super Storms occur every 100 to 200 years in California. The most recent super storm was in 1861-62 and lasted 45 days.  Massive floods resulted.  The Sacramento Valley became an inland sea.

These storms cause far more damage than earthquakes. The State of California estimates the next storm could cost $725 Billion dollars (NRA).

The effects would ripple out to the rest of the United States: California produces nearly half of U.S.-grown fruits, nuts, and vegetables; and across the nation, U.S. consumers regularly purchase several crops produced solely in California.

The USGS has dubbed such a storm an “ARkStorm” and held a conference in January 2011 to present the findings of more 117 scientists, engineers, and other experts of how such a storm would affect California.  A super storm might produce 10 feet of rain, overwhelming flood-protection systems.  Climate change will increase both the likelihood and severity of these storms.

Here are the likely effects of such a storm

  • 25% of all homes damaged in California from flooding and landslides
  • $300 billion property damage mostly from flooding
  • $400 billion damage to Agriculture and landslide damage
  • $325 billion in business interruption costs
  • A grand total of about $1 Trillion damage of which $20-30 billion would be recovered through insurance (public and commercial)
  • Most costly disaster in USA history
  • Hurricane force winds up to 125 miles per hour
  • Thousands of square miles of agricultural and urban land flooded up to depths of 20 feet.
  • Central Valley flood likely to be 300 miles long and 20 or more miles wide
  • Hundreds of landslides would cover roads, highways, and homes
  • Power outages, water and sewer infrastructure could take months to repair
  • Unemployment rate would increase by 6%
  • The levee system is likely to be overwhelmed, flooding some of the best agricultural land in the world, poisoning the drinking water with pesticides, manure, and other chemicals of up to 22 million Californians.
  • 1.5 million people would need to be evacuated.  The most populous areas affected are parts of the San Francisco Bay Area, and Orange, Los Angeles, and San Diego counties.

Effects of 1861-62 storm

  • California went bankrupt after a third of California’s taxable land was wiped out
  • Lakes formed in the Mojave Desert and Los Angeles Basin.
  • Even larger storms occurred in 212, 440, 603, 1029, 1418, and 1605.


Achenbach, J. 13 May 2011. The Century of Disasters. Meltdowns. Floods. Tornadoes. Oil spills. Grid crashes. Why more and more things seem to be going wrong, and what we can do about it.

Bwarie, J. 2011. ARkStorm: California’s Other “Big One”. USGS.

Balassone, M. 25 Feb 2011. USC Economist: California Superstorm Would be Costliest U.S. Disaster. USC News

Dettinger, M. June 1, 2011. Climate Change, Atmospheric Rivers, and Floods in California – A Multimodel Analysis of Storm Frequency and Magnitude Changes (pages 514–523).   Journal of the American Water Resources Association.

8 Mar 2011. California Superstorm Would Be Costliest US Disaster.

Mackenzie, D. March 30, 3013. Skyfall. NewScientist.

NRA (Natural Resources Agency). 2013. Safeguarding California: reducing climate risk. An update to the 2009 California climate adaptation strategy. Public draft. State of California. 289 pp

USGS & US Dept of the Interior. 2011.  Overview of the ARkStrom Scenario. Open file report 2010-1312. 201 pages.

Appendix A. crop and livestock estimated damages by county.
USGS & US Dept of the Interior. 2011.  Overview of the ARkStrom Scenario. Open file report 2010-1312. 77 pages.

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