Megastorm Could Result In Californian Megaflood

Talk of flooding to an Australian these days and you’ll discover just how affected we all were by the 2010–2011 Queensland floods. Nearly forty people lost their lives and $30 billion AUD was racked up in damages.

New geologic evidence should similarly concern residents of California according to an article in Scientific American entitled ‘California Megaflood: Lessons from A Forgotten Catastrophe‘.

Megastorms Could Cause Megaflood Problems for California
Inundation of the State Capitol, City of Sacramento, 1862
Image Source: Sacramento History Online

The evidence and research tells the story of a megaflood which struck the American West during the winter of 1861-62. The flood turned massive portions of California into inland seas for months at a time and took thousands of lives with it.

Needless to say, California’s population has grown somewhat over the past 150 years, with more than six million people living in the Central Valley.

1.4 million people live in Sacramento, which during the 1861-62 flood was covered underneath 10 feet of water, water filled with the mud and debris from innumerable mudslides.

Unsurprisingly the Native American living in the region preceding the flood took for the hills several weeks prior to the onrushing Pacific storms which slammed into the west coast of North America from Canada down to Mexico.

B. Lynn Ingram, one of the authors of the Scientific American article, quoted a January 11 piece from the Nevada City Democrat paper describing the Native American response;

We are informed that the Indians living in the vicinity of Marysville left their abodes a week or more ago for the foothills predicting an unprecedented overflow. They told the whites that the water would be higher than it has been for thirty years, and pointed high up on the trees and houses where it would come. The valley Indians have traditions that the water occasionally rises 15 or 20 feet higher than it has been at any time since the country was settled by whites, and as they live in the open air and watch closely all the weather indications, it is not improbable that they may have better means than the whites of anticipating a great storm.

What did the Native Americans notice that the ‘whites’ didn’t? We know it today as an “atmospheric river” and Wikipedia opens its article on the topic summarising four separate journal articles;

An atmospheric river is a narrow corridor or filament of concentrated moisture in the atmosphere. Atmospheric rivers consist of narrow bands of enhanced water vapor transport, typically along the boundaries between large areas of divergent surface air flow, including some frontal zones in association with extratropical cyclones that form over the oceans.

The water vapour image below from the GOES 11 satellite shows a long atmospheric river aimed across California from December 2010.

Image Source: United States Naval Research Laboratory, Monterey (Public Domain)

Why this look back into history? Simply put, Californians are placing themselves in more and more dangerous locations as they spread out across the state; the suburban crawl extending further and further into flood plains likely to be swept asunder if faced with another 1861-62 flood.

Articles like the Scientific American piece by Ingram will hopefully draw attention to necessary policies and research to prepare locations such as California — and others around the world — for the return of historical floods like the 1861-62 flood.

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