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Winter is coming, and so is the rain: Erosion control during vineyards’ off-season

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The winter season is officially upon us, and the rainy weather has prompted Napa Valley’s vineyard crews to reinforce their properties’ anti-erosion measures.

While keeping your vineyard from washing out is important for obvious practical reasons, rain carrying sediment to the valley floor and into the waterways negatively impacts the terroir as well.

County regulations require most vineyards to work with a civil engineer and establish an Erosion Control Plan before obtaining necessary construction permits, and various restoration projects and certification programs have emerged over time to keep Napa’s soil intact and waters clean.

“Not everyone knows about Napa County’s Conservation Regulations, and on top of that, the lengths grape growers go to to winterize their property and protect the watershed from soil erosion,” says Molly Moran Williams, Industry & Community Relations director at the Napa Valley Grapegrowers. “The recent, historic atmospheric river conditions doubled with fire-scarred areas could’ve been a perfect storm for disaster,” she said.

“Instead, it was a success story about what has been achieved through continued focus on conservation in a community.”

Erosion control measures haven’t always been on the minds of vineyard owners, though, and even when they were, properties historically have relied on less-than-effective methods that have since been phased out.

“The erosion control plan really took effect in the ‘90s when it became more concerning, especially with terraces that were in areas with really steep slopes,” said Justin Leigon, viticulturist for Piña Vineyard Management. “The terraces were not remaining intact, and it was causing issues, so it's been really nice to see that move toward a more soil health focus.”

Leigon says that terraces are not as easy to manage because the water has a tendency to build up, and then you have to find a way to filter it out and around the vineyard into a storage basin of some kind.

Nowadays, he says that the civil engineers his company works with often develop the plan by looking at the slope, overall soil type and terrain, and then help his crews determine the best places to put down straw or build a diversion ditch.

“I think a lot of it is just our understanding, and our current knowledge is different now than it was then,” he said. “We’re always adapting and evolving and learning more about what best practices are.”

At Premiere Viticultural Services, the sentiment is similar.

“In a lot of cases, the number one thing we can do for a property is to slow water down so we don’t create surface flow that will start to dig into and erode our soils,” said Garrett Buckland, partner at Premiere. “With the case of rain that we just had, even if you are on a relatively flat vineyard, you can get real erosion and concentrated flows,” he explained.

“Water can really speed up over those areas and pick up a lot of sediment and material and deposit it in other places … If that is going to happen, we want that to stay on our property before it gets into a waterway so we can keep sediment out of the waterway.”

Premiere also uses straw wattles -- which Buckland says look like skinny burritos -- which are essentially tubes of plastic mesh stuffed with straw.

“They basically serve as a tool for us to put out on the contour, and they will intercept water and filter it and slow it down,” he said.

Premiere also uses straw bales placed in strategic areas to slow water down and create “mini speed bumps,” for water all across the property. As per county regulations, Buckland says they have to have all of their properties winterized by Oct. 15 — Sept. 15 for those in a municipal watershed — which he says is fairly advanced but beneficial.

“We don’t normally see big rainfall events until we get to the tail end of October, so it is designed to have all of these erosion control things in place prior to any of these big storms,” he said.

And while these intervention measures are helpful in preventing soil erosion, Buckland says that if he were handed a raw piece of property, the goal would be to design something that didn’t require putting in straw wattles.

“So looking at a property, there’s sort of two ways: the hardcore engineer way, which is to put up a dam and flow this down and control it and have a valve here and there …. But we’re looking for natural ways to slow this down,” said Buckland. “Having a permanent cover crop, where we can cover at least 80 percent of the ground cover, is really the best way to slow down water.”

After last month’s heavy rainfall, Buckland gives credit to practices like cover crop, the use of straw and diversion ditches for avoiding water-related issues, and other than fire-scarred areas, says he didn’t hear of any major problems in his or his peers’ vineyards.

“What we have been doing for the last 30 years is working, and we should be carrying our story to the rest of the growing regions in the world,” he said.

You can reach Sam Jones at 707-256-2221 and

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Napa Valley wine industry reporter

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