The 5 Largest Flash Floods in California

Written by Dayva Segal
Published: October 3, 2022
© Danaan/Shutterstock.com
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California is a state that is in a near-perpetual drought. Water is always on everyone’s mind. The dry climate also leads to wildfires that have been getting more severe with each passing year. So, you might not associate California with flash floods. However, these dry and fiery conditions make certain areas of the state uniquely vulnerable to flash floods, and there have been some doozies in the state. Keep reading to find out more about the largest flash floods and the worst flash floods in California.

1. The Great Flood of 1862

Great flood of 1862 California
The flood was as a result of atmospheric river storms.

©published by A. Rosenfield (San Francisco) / public domain – License

This is still considered one of the worst floods in California to this day, even though it happened 150 years ago. In general, California receives most of its rain in the winter months. However, this year, between 24 to 37 inches of rain fell (depending on the area) between December and January. The state received a whole year of rain in just one month. This led to devastating floods.

California is often subject to “atmospheric river” storms. These storms are basically like rivers in the sky. They move water from tropical areas and dump the water as rain wherever they pass over. They carry as much water vapor as the Mississippi River in some areas. When an atmospheric river hits California from Hawaii, it is called a “Pineapple Express.” While they sometimes cause flooding and destruction, they are not all bad. Atmospheric rivers contribute positively to the snowpack in the Sierras, and thus, the water supply.

Most atmospheric river storms stay for a few days, dump a bunch of rain, and move on before weakening and cooling over the Sierra mountain range. However, this one stayed for 43 days in a row. Lakes and rivers formed in the desert as well as the city of Los Angeles. The Sacramento and San Joaquin valleys were entirely underwater. The state relocated the capital from Sacramento to San Francisco for a year and a half due to the resulting damage. It’s not known exactly how many people died but estimates are in the thousands. Over 200,000 cattle drowned in the Los Angeles Basin.

2. 2017 California Floods

2017 California Floods
The floods in 2017 caused damage to lives and properties.

©Danaan/Shutterstock.com

In 2017, the state of California saw its wettest winter since 1982. On a positive note, this winter ended a drought that had been going on for several years. However, this winter caused many floods throughout the state, and also caused a near disaster at the Oroville Dam.

  • The Russian River rose 3 feet and flooded 500 houses in Sonoma and Mendocino Counties. Over 500,000 people lost power during this flood.
  • The town of Maxwell in Colusa County had a flash flood on February 18th. Over 100 residents required boat rescues.
  • In San Jose, the Anderson Dam Creek overflowed and 14,000 people had to be evacuated. The damage cost $73 million.
  • The Oroville Dam Reservoir rose so quickly that it overflowed into the emergency spillway, and the spillway also overflowed. 188,000 people had to be evacuated in case the spillway completely failed. If it had failed, it would have sent a 30-foot wave of water into the Feather River and caused a devastating flood. Luckily a disaster was averted but the repairs cost over $1 billion.
  • In Los Angeles, 5 people drowned in flash floods that quickly overtook highways and created mudslides. Over 100,000 people lost power. In the Sun Valley neighborhood of Los Angeles, the water over I-5, the major highway, was over 2 feet deep.

Other areas also experienced flash floods, mudslides, and other weather-related issues. However, on the positive side, lakes and rivers that were running dry got some much-needed replenishment. This also led to dangerous conditions in the summer. Rivers were more full than usual and 14 people using the rivers for recreation drowned that summer.

3. 1982 SF Bay Area Floods

Flood, Bridge - Built Structure, Sandbag, Climate Change, Accidents and Disasters
More than 38 inches of rain were dumped as a result of the storms.

©iStock.com/DNBSTOCK

In the winter of 1982, storms fueled by the El Niño weather pattern dumped more than 38 inches of rain over the San Francisco Bay Area. The San Pedro Creek near Pacifica overflowed and flooded the seaside Linda Mar neighborhood. Other creeks in nearby Marin, Santa Cruz, Contra Costa, and Sonoma counties flooded creating dangerous conditions over a large area of land. The flooding caused mudslides that closed the iconic Golden Gate Bridge. Many roads were not passable and unfortunately more than 30 people died as a result of the flooding.

4. 2022 Tropical Storm Kay

 Accidents and Disasters, Beach, City, City Life, Climate
Tropical Storm Kay caused mudlsides and floods in California.

©iStock.com/Kelvin Cheng

It’s rare for a Pacific tropical storm or hurricane to hit California. They typically hit further down in Mexico. However, in September 2022 residents of Southern California were lucky enough to get torrential rainfall from Tropical Storm Kay in the middle of a drought. Unfortunately, the parched and scorched land conditions led to mudslides and flash floods. In San Bernardino County, several people had to be rescued from raging flash flood water. One person remains missing in that area. In Los Angeles, 50 people trapped by mudslides caused by the flooding were successfully rescued.

5. 2022 Death Valley Flash Floods

Flood, Death Valley National Park, Accidents and Disasters, Brown, California
About 1,000 people were stranded due to the flood.

©iStock.com/kittka

In August 2022, Death Valley National Park, home to the hottest place on earth, experienced a once in 1000 years flooding event. A year’s worth of rain fell in 3 hours. It was only 1.46 inches, but in a parched desert, that is a lot for such a short amount of time. Luckily there were no reported deaths or injuries, but flash floods devastated much of the park. 30 miles of the highway running through the massive park were impassable and covered in debris. 60 vehicles were buried by mud and debris. More than 1,000 people were trapped inside the park because the roads were not drivable. Park infrastructure was also damaged. Flood waters filled offices and hotel rooms at the park and pushed dumpsters into cars.

The Future of Flash Floods in California

Climate scientists believe that it may not be a huge earthquake or devastating drought that will cause the most damage to California. They believe that it is more likely than ever that a huge flood will hit the region. These experts say climate change could cause atmospheric river storms to stay for weeks instead of days, as they did in 1862. They believe an event like this would cause over $1 trillion in damage at this point. It would once again turn the Central Valley area of the state into a lake. That storm 150 years ago caused the state to declare bankruptcy. At that time, only 500,000 people lived in the state. Now more than 40 million people live in California, meaning the danger to lives and livelihoods would be exponentially greater.

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2017 California Floods
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About the Author

I'm a freelance writer who has been working in the field of content creation and digital marketing for more than seven years. My favorite topics to write about include health, animals, fitness, and nutrition, though as a professional content provider and ghostwriter, I can easily write about pretty much anything! I love all animals and have been some form of vegetarian or vegan for over 10 years. My favorite animals are cats, dogs, and chickens, especially my own cat, Tula.

FAQs (Frequently Asked Questions) 

What was the worst flood in California?

The Great Flood of 1862 is still considered one of the worst floods in California to this day, even though it happened 150 years ago.

What caused the Great Flood of 1862?

The Great Flood of 1862 was caused by an atmospheric river storm that stayed over California for 43 days.

How many people died in the Great Flood of 1862?

It’s not known exactly how many people died but estimates are in the thousands.

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