ADAPTATION GUIDE

Disaster History in a nutshell:

"Atmospheric Rivers"

Fellow citizens, we cannot escape history.

-Abraham Lincoln

The phenomenon is best studied on the US West Coast. Historical records attest to the power of "atmospheric rivers" in that region.

The century's storm of the winter of 1861/62 particularly alarms researchers.

On Christmas Eve of that year, the heavens opened their floodgates over California.

In the ensuing weeks, everything unfolded as if from the pages of the Bible - only without an ark. For 45 days, heavy rain clouds traversed the land. Lakes formed in the Mojave Desert and the Los Angeles Basin.

Storms raged almost along the entire North American West Coast, from British Columbia down to Mexico. The Central Valley transformed into a sea of mud, 500 kilometers long and 30 kilometers wide.

An estimated 200,000 cattle drowned. "Thousands of farms are completely underwater," reported author William Brewer, who traveled the land at that time. In some places, not even the tops of telegraph poles protruded from the water.

The sludge stood three meters high in the downtown of the Californian capital, Sacramento. The newly elected governor, Leland Stanford, reached his inauguration by rowboat. During the ceremony on January 10, 1862, the water kept rising.

On the way back, the dignitary could only enter his residence through a window on the first floor. It was not until three months later that the murky water receded.

By then, the state was bankrupt. "The catastrophe is part of the punishment for our national sins," preached S.C. Thrall, a priest in San Francisco. Whether it was God's wrath or not, it is now established that the century's flood doesn't even rank among the worst in recent history.

The soil of California reveals how uncomfortable it could truly become. To obtain sediment cores, geologists drove their drill bits into marshes and meadows around the Bay of San Francisco.

The profiles unveiled a dramatic past. For example, two superstorms flooded the land at the beginning of the 12th and 15th centuries.

Especially destructive, however, was a storm that swept across the land in the winter of 1605. The floods deposited at least ten times as much sediment as the worst storms of the previous century.

"Atmospheric rivers" are massive bands of moist air currents that form over the oceans and can extend for several thousand kilometers. They transport moist, warm air from the tropics to temperate latitudes and unload their water load on the west coasts of continents.

Over mountain ranges, the air masses rise, cooling in the process. The contained water vapor condenses, leading to heavy rainfall. In the worst case, successive storms can rage for several weeks.

The result: rivers overflow, and coastal plains are extensively flooded.