Unseasonably warm temperatures this week are expected to rise into the mid-70s for parts of Northern California. Historically, winter tends to start inching its way into California around the holidays, with temperatures in the 60s and regular threats of precipitation.
Nearly 66 years ago, a devastating flood in Northern California caused more than $32 million in damage and was responsible for nine deaths, according to the California Governor’s Office of Emergency Services (Cal OES). It was the region’s worst flood on record until 1997, when a series of subtropical storms in Northern California caused severe levee failures.
The floods of November and December of 1950 initiated when a series of meteorological events in the final days of October caused heavy rain across the northern end of the Sacramento Basin and extended as far south as the American River.
A mixture of 1-3 inches of rain and snow fell from the Yuba River south to the Kern River in mid-November, and snow blanketed down the Sierra Nevada slopes to approximately 4,000 feet in the Sacramento Basin, 6,000 feet in the San Joaquin Basin and western Nevada, and 7,000 feet in the Tulare Basin.
Even so, the hardest of the rain and snow had yet to arrive.
Just a few days later, some basins received as much as 13 inches of rain while an average of 11 inches fell on all of the mountain watersheds from Yuba River in the north to Kern River in the south. As much as 10 inches of rain fell in 12 hours. Warm rain melted away on shallow snow cover and set off record-breaking flood peaks on almost all of the mountain streams.
Another storm preceded a stretch of nearly a week-and-a-half without any precipitation. In early December, though, a warm storm brought about 4-5 inches of rain in the Sacramento Basin and 2-3 inches in the San Joaquin Basin.
Minimal rain fell for the rest of the month of December, but by then the damage had already been done.
Throughout the series of storms, the Yuba and American basins absorbed 30 inches of rain. The San Joaquin Basin received 25 inches of rain, with the Truckee Basin totaling 20 inches and the Tulare Basin accumulating 15-20 inches. The cumulative effect of persistent precipitation was extremely rare for the early stages of winter, likewise for warm temperatures that caused rain to fall at unusually high elevations. More problematic, the continual string of storms did not allow the watersheds to dry out, thus putting stress on almost every major stream of the Sacramento and San Joaquin basins and the western Nevada area.
The overflow from streams flooded more than 245,000 acres in the Sacramento Basin, while the San Joaquin Basin consumed 226,000 acres. The total flooded area in the Tulare Basin amounted to 198,000 acres, and western Nevada had 41,000 acres under water.
As winter approaches, massive flooding in California remains a constant threat, along with mudslides in burn-scarred areas. Since 1950, there have been at least eight other significant flooding disasters in California, including the 1997 New Year’s Day flood in Northern California. More than 23,000 homes, businesses and other infrastructures were damaged. Nine people died and an additional 120,000 people were evacuated from their residences.
Flash floods are the No. 1 cause of weather-related deaths in the United States. Educating yourself on disaster preparedness and knowing what to do in the event of a catastrophic flood could provide life-saving tips.
Here are a few suggestions, courtesy of Ready.gov, on how to be prepared for a flood:
- Avoid walking or driving through flood waters.
- Just 6 inches of moving water can knock you down, and 2 feet of water can sweep your vehicle away.
- If there is a chance of flash flooding, move immediately to higher ground.
- If floodwaters rise around your car but the water is not moving, abandon the car and move to higher ground. Do not leave the car and enter moving water.
- Avoid camping or parking along streams, rivers, and creeks during heavy rainfall. These areas can flood quickly and with little warning.
Additional flood resources: