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Yet another natural disaster in the offing for California

By Michael Evans - 26 Jan 2011 11:55:0 GMT
Yet another natural disaster in the offing for California

We are all familiar with the long predicted scenario of a major Californian earthquake. Since records began in 1769 violent shocks have regularly resulted in considerable damage and significant loss of life.

Perhaps the most famous came on 18thApril 1906, when 700 people died and raging fires helped to cause property loss of over $500 million. This event was dramatically portrayed in the 1936 Clark Gable film, San Francisco.

In 2008 scientists predicted that there was a 99% chance of a major earthquake of magnitude 7.5 or greater occurring sometime within the following 30 years. This means that there are now 27 years left, but it could happen tomorrow.

As if this were not enough, scientists have now unveiled a scenario that describes how a hypothetical storm could hit California and produce up to ten feet of rain, causing extensive flooding and damage to the tune of nearly $400 billion.

The “ARkStorm Scenario”, from Atmospheric River 1000, was prepared by the US Geological Survey (USGS) and released at the recent ARkStorm Summit in Sacramento. It combines prehistoric flood history in California with modern flood mapping and climate-change projections to produce a hypothetical but plausible scenario.

More than 100 scientists spent two years developing the scenario and Lucy Jones, the architect of ARkStorm, said the scenario gives a complete picture of what would happen to the social and economic systems of California in the event of an extreme metrological event being followed by landslides and flooding. “We think this event happens once every 100 or 200 years,” she said, “which puts it in the same category as our big San Andreas earthquakes.”

This hypothetical storm would be similar to the intense winter storms of 1861 and 1862 that left the central valley of California impassable. Flooding would be the major outcome of the storm, with a quarter of Californian houses being affected. Over 6000 square miles of the Central Valley would be flooded, along with Orange County, Los Angeles County, San Diego and the San Francisco Bay Area.

Wind speeds in some places would reach up to 125 miles per hour, with 60 miles per hour being the norm over a wide area. Hundreds of landslides would damage roads and homes. 1½ million residents would need to be evacuated, repair to power lines, water mains and sewer systems could take months and business interruption costs could run to $325 billion. With $400 billion for property repair costs, the total would come to $725 billion, nearly three times the expected loss from a major earthquake.

Marcia McNutt, USGS Director, was clear about what should be done. “The time to begin to take action is now, before a devastating natural hazard event occurs.” She went on to say that the scenario demonstrates at first hand how science can be a foundation to help build safer communities. “This is a scientifically vetted tool that can be used by emergency responders, elected officials and the general public to plan for a major catastrophic event to prevent a hazard from becoming a disaster.”

Image © victor zastol'skiy