FORESTVILLE, Calif. — The heaviest rain in a decade overwhelmed parts of California and Nevada on Monday, dumping more than a foot of water on parts of Northern California. The storm forced hundreds of people to flee and left thousands without power.
The system pushed rivers over their banks and toppled many trees — among them the fabled giant sequoia dubbed ‘‘Pioneer Cabin’’ that had a tunnel carved into its base more than a century ago.
The sequoia, at the Calaveras Big Trees State Park about 90 miles east of Sacramento, was one of several tunnel trees in California, created as tourist attractions in the 1880s.
Forecasters said another strong storm was bearing down on the two-state region for Tuesday.
Emergency crews in boats and helicopters rushed to take advantage of a one-day break between storms Monday to rescue stranded people and assess damage.
Such gaps between storms are ‘‘what saves us from the big water,’’ Fire Chief Max Ming said in the Russian River town of Forestville, where rescuers launched rafts and used a helicopter to search for people cut off by rising water. ‘‘People hunker down and wait for it to get past.’’
The storms that started in California and Nevada last week are part of an ‘‘atmospheric river’’ weather system that draws precipitation from the Pacific Ocean as far west as Hawaii. That kind of system, also known as the ‘‘pineapple express,’’ poses catastrophic risks for areas hit by the heaviest rain.
‘‘It’s been about 10 years since we’ve experienced this kind of rainfall,’’ said Steve Anderson, a National Weather Service forecaster. ‘
Parts of California’s wine country in Sonoma County were among the hardest hit, with up to 13 inches of rain since Friday, Anderson said.
The Russian River in Sonoma rose to its highest level since 2006, spilling over its banks and into vineyards and oak groves. Schools and roads were forced to close across the area.
Avalanche concerns kept some California ski areas closed for a second day Monday in the Sierra Nevada. Forecasters said more snow and rain was on the way.
The Russian River is prone to flooding, but this year’s flood has been particularly worrisome because it threatened to topple trees weakened by six years of drought.
A flood warning for the Russian River was in effect, along with a high wind watch planned for Tuesday afternoon through Tuesday evening, Anderson said.
Jim Allday, a park volunteer at Big Trees State Park in Calaveras County, told the SF Gate website that the Pioneer Cabin tree fell around 2 p.m. Sunday and “shattered’’ as it hit the ground.
Cars were once allowed to drive through the tree tunnel, but in recent years, it was accessible only to hikers on a 1.5-mile loop through the park, according to the U.S. Forest Service.
A giant tree fell across a highway in Hillsborough to the south of San Francisco, injuring a driver. And a woman was killed Saturday by a falling tree while she took a walk.
Yosemite National Park will reopen the valley floor to visitors Tuesday morning after it was closed through the weekend and Monday because of a storm-swollen river, park spokesman Scott Gediman said.
Over the weekend, toppled trees also crashed against cars and homes and blocked roads in the San Francisco Bay area. Stranded motorists had to be rescued from cars stuck on flooded roads. The city itself got just over 2 inches of rain.
To the south near Los Angeles, commuters were warned of possible highway flooding and mudslides in hilly areas.
Emergency workers in Nevada voluntarily removed about 1,300 people from 400 homes in a Reno neighborhood as the Truckee River overflowed and drainage ditches backed up.
Winter storm warnings were in effect in the Sierra Nevada until Thursday morning, with the potential for blizzard and white-out conditions. Four to 8 feet of snow are forecast through Thursday above 7,000 feet, and the Lake Tahoe area could get between 2 to 5 feet of snow.
