The U.S. Geological Survey recently released its next Multi Hazards Demonstration Project, a cataclysmic scenario called ARkStorm that would hit the West Coast. The 200-page document anticipates precipitation levels only experienced once every 500 to 1,000 years.
Cities in Northern California played out the scenario last week, similar to the ShakeOut Earthquake drill undertaken by Southern California in November 2008.
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The ShakeOut Scenario depicted the immediate and subsequent effects a 7.8 magnitude earthquake would have for areas along the San Andreas Fault.
In the case of ARkStorm, USGS scientists designed a meteorological event followed by an examination of flooding, landslides, physical damages to the built environment, social effects and economic consequences.
The hypothetical storm would be similar to the intense weather that hit the West Coast in 1861 and 1862.
“The scenario is a catastrophic flooding event that’s mirrored after the floods in the 1860s in Northern California,” said Donna Nuzzi, Emergency Services Supervisor with the City of Santa Clarita. “They basically said, ‘This is the shakeout but related to flooding.’ ”
“A storm of this magnitude would dump volumes of water very fast and very quickly,” she said. “It just overwhelms the infrastructure, including reservoirs and flood channels.”
Since the Santa Clarita landscape is so unlike the flatness of the Great Plains, any impact would come from the runoff from nearby mountains and ridge lines, Nuzzi said.
“For us, the scenario would be similar to flash floods.”
In 2008, Santa Clarita, along with several other municipalities, participated in the ShakeOut Scenario, alerting the city to drop, cover and hold at the appropriate time.
“For (ARkStorm) we would have to rely on our mass notification system and texting and really doing a lot of pre-warning,” she said.
Nuzzi said that, although it’s difficult to prepare for a flash flood, residents need to inform themselves of what to do in such an event.
“The idea is the basics of getting to high ground and hopefully people are able to do that. Hopefully people without transportation are able to get some place away from an impact zone,” she said. “We have that with our modeling. We know what our impact areas are.”