LIVE OAK — In a sign that a vexing and locally contentious issue has reached a crisis level, a biennial census of homelessness shows the population soared 28 percent in 2013.

Sleeping in culverts and cars, behind driftwood and secreted deep into the woods, the number of homeless people living here is at a level that rivals major metropolitan areas. There are 3,536 people without an address, according to the census, enough to form a line stretching along 41st Avenue from Highway 1 to Portola Drive.

“If you can visually imagine that, it”s a pretty staggering trend,” said Peter Connery, vice president of Applied Survey Research, the Watsonville company that conducted the survey.

The homeless count is conducted every two years, partly to maintain the county”s eligibility for federal homeless grants. But the report also provides insight into the local homeless population, and the picture isn”t pretty.

There are more homeless youths younger than 25 years old living on the streets here — 947 — than there are in San Jose, a city with nearly four times the population. And it is half the number found on the streets of San Francisco, even though those two cities, unlike Santa Cruz County, have shelters for homeless minors.

Further, the county and its overwhelmed service providers are doing a woeful job of providing shelter. Just 18 percent of the homeless population was under a roof when the census was taken in January — one of the worst figures in the country — and that number includes about 100 seasonal beds at a former National Guard Armory in Delaveaga Park.

The inadequacy of local services was underscored by Renee Delisle, who was homeless and living with her partner on the street when she found out she was pregnant. She was later turned away from a shelter that did not have space for her, and the family found an abandoned elevator shaft to live in.

“We slept in an elevator up until my water broke,” said Delisle, who now lives in transitional housing through Pajaro Valley Shelter Services.

But one big question remains: why?

“One of the things we don”t really understand is why things increased so significantly from 2011 to 2013. There”s a whole constellation of issues that contribute to it,” Connery said.

One factor is certainly the foundering local economy, with job growth lagging the rest of the Bay Area and being particularly high in Watsonville. During the most-recent fiscal quarter, the county also handed in one of the worst wage-growth figures — at -3.4 percent — in the country, according to the Bureau of Labor Statistics.

“It”s not just housing,” said Carolyn Coleman, executive director of Encompass Community Services. “The employment piece is really critical.”

Further, the point-in-time count understates the magnitude of how many people are living on the fringe here. Many thousands more are likely to go homeless for at least part of the year, and a recent county Community Assessment Project survey showed about 8,800 local households were hosting someone that might otherwise be counted as homeless.

Among other findings:

28 percent lived in vehicles, a much higher figure than in surrounding communities.

32 percent were women, also higher than in surrounding areas.

44 percent said they were homeless for the first time, slightly lower than in surrounding areas.

About 1-in-5 were employed in some capacity, in line with numbers elsewhere.

68 percent reported a disabling condition, including 55 percent with mental illness and 26 percent with substance abuse problems.

Nearly 3-in-10 spent time in jail in the last year, in line with surrounding areas.

69 percent received some form of government assistance, typically CalFresh, slightly higher than elsewhere.

11 percent were military veterans, lower than the national average.