(LATimes) - Jason Haas' plan for El Niño involves oats, sweet peas, vetch, clover, sheep, alpacas, a llama and a couple of donkeys.

It's not for everyone, the organic viticulturist admits. But it works for his family's Paso Robles vineyard, where dormant vines have laid bare acre after acre of precious topsoil on steep hillsides.

If all goes well, gentle rains will coax out a lush cover crop to protect from a deluge, and the odd menagerie will slowly nibble it to a nub by spring, when the vines revive.

"We've already gotten three small storms that have come through and dumped about half an inch of rain each," said Haas, partner and general manager of Tablas Creek Vineyards in Paso Robles. "The cover crop is sprouted. That's going to do a big piece to hold the soil in place."

Across California's wine regions, growers are hoping a tenuous cover crop and ample straw will keep their nutrient-rich topsoil in place through what may be the first very wet winter in more than four years.

Atmospheric scientists have said the shift in Pacific Ocean currents that sparks the global weather phenomenon known as El Niño will bring a greater-than-even chance of above-normal rain across the center of the state. That makes the topsoil on steep hillside vineyards around Paso Robles more vulnerable than the more moderately sloped acreage in Napa and Sonoma, where growers are accustomed to higher rainfall.

Not far from Haas' farm, relative newcomer Jason Yeager is staring down what could be the first wet winter his vines have seen since he planted them five years ago. But he grew up in a wine family in Napa, where putting in a cover crop is standard operating procedure.

"Down here it's starting to become that way, and we're trying to get the word out to other growers that may not do that sort of thing to spend a little money and put a little something in there, because if they don't, it's going to be a problem," said Yeager, director of vineyards at Niner Wine Estates in Paso Robles.

"As farmers, we're all interested in keeping our soil right in place. That's how we make a living," said Garrett Buckland of Premiere Viticultural Services, a consulting company in Napa. "It doesn't do us any good if it's out in the bay somewhere."

The Central Coast had a dress rehearsal in July, when the remnants of a Pacific hurricane dumped 3.55 inches of rain around Paso Robles. "Everything was bare," Yeager said. "You're never expecting that kind of rain in July here because it just never happens. I had quite a mess to clean up here."

One walnut grower lost tons of topsoil from a recently tilled property west of the city.

"You can lose hundreds of tons of topsoil from a downpour like that," said grower and vintner Matt Merrill, general manager of Mesa Vineyard Management Inc. in Templeton, which oversees about 12,000 acres of vineyards in the Central Coast region.

Properties he manages are putting down hay and a cover crop, clearing ditches and drains and taking other measures to prepare, Merrill said.

"A lot of the vineyards we manage now have gone to having a permanent cover crop, so you don't go through and disc it up and disturb the soil," Merrill said. "It seems like, industrywide, people are prepared and expecting it — and hoping that it does come true, that there's all this rain coming. "