California housing costs are spiraling so high that they are pushing the state’s homelessness crisis into places it’s never been before — sparsely populated rural counties.

A Chronicle analysis of biennial homeless counts taken early this year across California shows the sharpest increases occurred not in San Francisco and other urban centers but in out-of-the-way places such as the thickly forested Sierra Nevada and the dusty flatlands and low hills of the northern Sacramento Valley.

Statewide, The Chronicle’s examination shows, homelessness rose by 15 percent from 2015 to this year. In heavily populated centers such as Los Angeles and the Bay Area, where tent cities have long been part of the landscape, even double-digit increases like that might not suggest that something has fundamentally changed. But in rural areas, the increases have come as a shock.

When the number of people without homes in the historic Gold Rush territory of El Dorado County climbs 122 percent in two years, and the farmlands of Butte County see a 76 percent rise, it’s jarring to neighbors, community leaders, police and homeless people themselves. Those counties lack the years of experience that cities have in creating services for homeless people and are starting almost from scratch.

There is no year-round shelter in El Dorado County , and camps are multiplying on the edges of the county seat of Placerville. In Butte County , the few shelters are overwhelmed, and panhandlers who were once an anomaly in the college town of Chico are becoming commonplace.

It’s the same story in places like Lake County, north of the Bay Area; Shasta County, on the slopes of the Cascades; and Imperial County, along the Mexico border — all rural enclaves where housing that used to be cheap has suddenly become less affordable and where homelessness has spiked.

For many low-income residents of such counties, with few shelters or services to turn to when they lose their homes, there’s pretty much nowhere to go but outside. And with a traditional intolerance of downtown drifters, that usually means into the forests, gullies and fields.

“I had a grocery store job and I had a home, but when I had to leave my apartment about a year ago because of domestic violence, I found that whatever I used to be able to afford, I just couldn’t afford anymore,” said 46-year-old Charisse, who did not want her last name used for fear of her former boyfriend. “You can’t even put together first and last month’s rent unless you have a really high-paying job. We’re stuck.”

Charisse sleeps in a camp at the edge of Lake Tahoe in El Dorado County, hidden at the end of a deer trail. She and her tentmates fish for their meals and go into nearby South Lake Tahoe infrequently “because they don’t like homeless people walking around there.”

“But there’s more and more of us every day, all people who live around here and lost our apartments for some crummy reason,” she said. “So they’re just going to have to get used to us.”

The federal Department of Housing and Urban Development, which conducts the biennial counts of homeless individuals, is scheduled to release its latest national homeless tally this fall. The Chronicle built its database for California by obtaining the counts for all 55 counties that performed tabulations. The calculations show that the increase in homeless people since 2015 has brought the total homeless population in California to a new high of 135,139 — the most of any state.

Experts blame the phenomenon of exploding rural homelessness on rising housing prices and rents and wages that have been stagnant for years. Those who study homelessness say the number of those without secure shelter will keep rising until something is done to create more housing that poor people can afford.

“It’s really hard to stop the flood of homeless people when you have to close the back door and the front door at the same time,” said Sharon Rapport, a national homelessness analyst with the Corporation for Supportive Housing. “A lot of people are becoming newly homeless, and we used to see that mostly in the big cities. But not so much now.

“It’s changing. We cannot stop the flood.”

San Francisco spends $305 million annually on homelessness, which has helped keep the city’s street population virtually flat over the past two years, at an estimated 7,500. But in El Dorado and Butte counties, officials say they are so new to dealing with homelessness that they don’t know how much they spend on the problem — only that it’s not enough. Until recently, they left the heavy lifting for handling transients to nonprofits like churches and charities.

“We can get people ready to move inside, but the lack of housing that’s affordable is really hurting people,” said Rene Evans, director of Only Kindness, the main nonprofit agency helping homeless people in El Dorado County.

“We have no year-round emergency shelter. There aren’t enough jobs up here in the mountains. That, and rents that are always getting higher, keep people circling down the drain so they can never get back up again.”

Statistics paint at least part of the picture. Since January 2015, median housing prices have shot up 37 percent in El Dorado County and 55 percent in Butte County , according to the CoreLogic financial analysis firm. Median rents also rose sharply, according to the real estate site Zillow — up 88 percent in El Dorado County and 53 percent in Butte County .

“I’d love to move back inside, but rent is off the hook around here,” said Marci Butler, 41, who lost her home in Placerville six months ago when her roommate moved out and she couldn’t pay the rent herself. “It’s terrible living in the trees, sometimes sleeping in my truck, not having a roof or a job.”

She has been staying at a settlement of tattered yurts outside the unincorporated community of Cameron Park with a half-dozen other women who fled abusive partners or lost jobs and were evicted. Like virtually every other El Dorado County homeless camp, it’s tucked into a cluster of pines and oaks well away from any road. At times the only sound is a nearby brook.

Butler was getting by on a small government disability check. While it used to be enough to swing her half of a $600 monthly rent, she figures that anywhere she moves now would cost closer to $1,000. It’s her first time outside, and she feels lost.

“We’re broken people, but we’re still people,” Butler said. “We need to know people still care. We just need some help to get back on our feet. But there just isn’t much here. If anything goes wrong, you’re out of luck.”

El Dorado County sprawls across 1,805 square miles from the Sierra foothills to Lake Tahoe. With a population of 185,625, it’s a magnet for retirees and tourists and has only two small cities, Placerville and South Lake Tahoe. Most of the 598 homeless people counted this year find spots around Placerville.

“I’ve never seen it this bad,” said Mike Beals, owner of Placerville Body Shop. “Every morning when I open up my business now, there’s someone sleeping in front of it. We lose customers.

“I know it sucks to be homeless, but they should just go to work.”

Such complaints have gotten El Dorado County officials’ attention. The county is creating what it calls its Coordinated Entry system, with the goal of aligning its homeless services to reduce duplication and do a better job of routing clients to where they need to go. It also procured $500,000 from the state to create its first permanent supportive housing units, which is housing with counseling on site for chronically homeless people.

But perhaps the most significant step the county took came in May, when it formed its first homeless outreach team to patrol homeless camps and connect people with aid. The team consists of three sheriff’s deputies, who have become more like social workers than cops.

“We’re not going to arrest our way out of this problem,” said team leader Sgt. Mike Cook, a narcotics specialist who has worked in El Dorado County for more than two decades. “We are all about real, permanent housing solutions. Getting people into rehab, into a place to live.”

In the nearly four months it has been on patrol, Cook’s team has helped house about a dozen people, including sending two to a drug rehabilitation center in San Francisco. Another dozen are on the cusp of moving inside.

Just like in the big cities, substance abuse and mental illness are rife among the hard-core homeless denizens of the rural parts of the state, meaning solutions require more than just scoring a bed.

A 50-year-old man who goes by the name Ra-Do and lives in a forest camp near Placerville said his first reaction when he encountered the outreach team was distrust. “But then I saw them help people,” he said. “And when somebody keeps stopping by, it makes you think.”

Ra-Do said he has been homeless off and on — between apartments and time in prison — for 15 years. When he lost his most recent housing a year ago, he said, rents in El Dorado County had gotten “way out of control, and I just can’t see how I could afford anything with whatever kind of job I might get.”

It’s a common problem, Blake Braafladt, a deputy on the outreach team, said as he hiked into Ra-Do’s camp. Braafladt had come to talk with Ra-Do about doing residential rehab for his struggles with methamphetamine and alcohol and then maybe living with a friend.

“I’d love to talk more,” Ra-Do told him.

“A guy like that — we’re trying to plant seeds with them,” Braafladt said as he walked away. “But we have to get creative about what kind of housing, what services we can talk about with them, because there’s not enough available and government moves really slow.”

Longtime antipoverty advocate Paul Boden of San Francisco, who works throughout the West, said he’s seen rural homelessness grow for several years as people chased lower housing prices from cities to suburbs to smaller towns.

California’s $10.50 hourly minimum wage is $3.25 higher than the federal mandate, but Boden and other experts estimate that still buys only about half of what a minimum wage did in 1980.

“What I’ve been seeing is reminiscent of the ‘Grapes of Wrath,’” said Boden, organizing director of the Western Regional Advocacy Project. “Homeless people in rural counties are definitely not city people — and they can’t be. You have food programs in one town, shelter in another, you have to walk miles and miles to get anywhere.”

Most of them, like city homeless people, were living in the same area they now camp in when they lost their roofs, according to studies done with the biennial counts.

In Butte County, low housing vacancy rates and rising rents get the most blame for spreading homelessness in an agricultural region heavy on walnuts and almonds.

Chico, with 92,464 people, is the county’s largest city by far, and accounts for the majority of the county’s estimated 1,983 homeless people. With the county’s rental vacancy rate hovering around 1 percent — California’s is 3.6 percent, an all-time low for the state — homeless people have nowhere to go, said Ed Mayer, executive director of the Butte County Housing Authority.

“We are simply not producing enough housing to meet the needs of the community,” Mayer said. “And the more expensive housing becomes, it just aggravates our problem.”

Shelter directors, housing authorities and police in Chico say it’s easy to see evidence of the jump in the homeless population.

Drifters dot downtown streets and City Plaza during the day and panhandle students at California State University Chico. Barred by ordinances from camping in the city, they retreat to creeks and the woods outside town at night.

The Chico Police Department’s Target group, similar to El Dorado County’s homeless outreach team, roams the area. The aim is to simultaneously offer them shelter and help, but many refuse, said Target Officer Paul Ratto.

David Delo sits on the same steps of the city plaza every day. He and his three friends lean against the bathroom, drinking 40-ounce bottles of Hurricane beer and smoking joints and cigarettes. Target team officers know him and his friends by name and have been trying to get them into a shelter. But they’ve had no luck.

Delo took a bus from Oklahoma City to Chico about eight months ago to stay with a friend, but he said that when he arrived his friend had left. Feeling hopeless about being able to rent anything even if he got a job, he’s been on the streets ever since.

“I’ve put applications out all over town,” Delo said. “But no one’s hiring an old hippie.”

Homeless camps are scattered throughout the forested hideaways around Lake Oroville and the adjacent Plumas National Forest, but there are just three shelters in the 1,600-square-mile county — two in Chico and one in Oroville. The shelters offer 200 beds and are always full.

In and around the tiniest towns, like Paradise and Magalia, homeless people migrate from the forests and fields to abandoned buildings or shacks when the brutal winter sets in, said Sherisse Allen, Butte County’s homeless services coordinator.

With no emergency shelters or other homeless services, the smaller towns look for whatever solutions they can — finding temporary spots in kindly people’s homes, renting hotel rooms or helping homeless people travel onward if they’re so inclined. Some homeless people from smaller towns drift down to Chico, but Allen said that’s rarer than people think.

Chico’s mayor believes the opposite. As the largest town around, he said, Chico is “a big magnet.”

“We have lots of service organizations,” Mayor Sean Morgan said. “We’re a very compassionate community. The students are compassionate. We have a first-rate hospital, we have a great climate and we got marijuana fields everywhere. We attract all these people. We see it every two years when there’s an election, people are screaming, ‘Clean it up, clean it up, clean it up!’”

One sobering aspect of the rising counts of homeless people in Butte County, El Dorado County and across the state is that they undoubtedly understate the problem. Experts have long argued that the one-night counts done once every two years cannot capture a true estimate of the population. A report released in July, from the University of New Hampshire, estimates that large cities in California undercount the unsheltered by more than 25 percent.

“All I know is, back when I moved here in 1967, the only people close to what they called homeless were drunk old men living in shabby rooms,” said 86-year-old Marylin Ferguson, manager of the Fountain and Tallman Museum in Placerville. “Now, all of a sudden in the past couple of years, you see them in the trees outside of town. I don’t know what the solution is. But it’s terribly sad.”

Kevin Fagan and Alison Graham are San Francisco Chronicle staff writers. Email: kfagan@sfchronicle.com, agraham@sfchronicle.com Twitter: @KevinChron, @alisonkgraham