In the 19th century, a massive storm in the pacific United States opened up a 300-mile-long sea that stretched through much of central California. From late 1861 to early 1862, it rained almost nonstop. Rivers running down the Sierra Nevada Mountains swept entire towns away. The storm was caused by a large concentration of water vapor known as an “atmospheric river.” Now, after years of drought, it looks like the state is due for another megaflood.

“These storms have the potential of hurricanes—or even more so because they go on for weeks,” Lucy Jones of the US Geological Survey told NPR.

Atmospheric rivers carry concentrated channels of water vapor out of the tropics and are capable of carrying more than 10 times the average amount of water that passes through the mouth of the Mississippi River. That is a massive amount of rainfall with the potential to cause devastating floods. In 1862, the flooding was so intense in California that the Central Valley actually turned into a massive inland sea.

“Thousands of farms are entirely under water—cattle starving and drowning,” William Henry Brewer wrote to his brother on the East Coast at the time. “All the roads in the middle of the state are impassable; so all mails are cut off. The telegraph also does not work clear through.”

“In the Sacramento Valley for some distance the tops of the poles are under water,” he continued. “The entire valley was a lake extending from the mountains on one side to the coast range hills on the other. Steamers ran back over the ranches fourteen miles from the river, carrying stock, etc, to the hills. Nearly every house and farm over this immense region is gone. America has never before seen such desolation by flood as this has been, and seldom has the Old World seen the like.”

Brewer was not exaggerating. In fact, one in eight houses were destroyed or carried away in the flood waters. As much as a quarter of California’s taxable property was destroyed, decimating California’s economy. And this mega storm could happen again.

The US Geological Survey has developed a project to assess how the state could handle another massive flooding disaster by studying a combination of two recent large storms—one in 1969 and one in 1986. It doesn’t look promising.

Source: Science Alert, Business Insider

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