Flooded Napa, Sonoma vineyards may not be a big problem during winter's nap, say experts

Images have been streaming around the globe of the rain-swollen Napa, Russian and Navarro rivers' overspilling their banks into vineyards of some of the California North Coast's most sought-after wine regions.

When people see vineyards with “wet feet,” they often inundate vintners and growers with “whether” questions, like whether vines are harmed by being in or under water.

“It's a great story, but this time of year, it does not bother anything,” said Duff Bevill, whose Bevill Vineyard Management company farms hundreds of acres in Sonoma and Napa counties.

That's the short answer he and other viticulture experts give. Basically, temperatures around freezing and less daylight put vines into sleep mode. Wading into the full answer of whether wet feet significantly hampers vine health or vineyard operations involves considering the stage of the vine's annual growth cycle, soil conditions, damage the water causes and how much flooding hampers field work.

Tom Gamble, owner of Gamble Family Vineyards, has seen a number of floods to the Napa Valley properties he and his predecessors have been farming for going on 102 years. He expects a few days of work cleaning minor damage from brush and other debris pushed against rows of vines from a flood earlier this month.

“Having experienced many floods, I'd rate floods this year - so far - as having created some headaches in my vineyards but far fewer than the floods of '05–'06, the '90s and '80s,” Gamble said. “Given the volume of water flows in the January floods, one would have thought [we'd have] bigger problems, based on these past experiences.”

CONTROL ISSUES

Navigating through that storm with minor problems was two parts luck and one part hard flood-control work among a number of Napa Valley growers, property owners and public agencies over the past decade, he said.

The luck part, Gamble said, was that storm's spreading of rain over time, rather than coming all at once, and that the tide wasn't exceptionally high during this period to stall the draining of Napa River into San Francisco Bay. The North Coast was bracing for three waves of soaker storms forecast to blow through Jan. 18–23, pouring as much as 3 more inches of rain into local waterways, according to the National Weather Service.

The hard work credited with few reports of the kind of riverbank erosion seen elsewhere in the state and keeping downtown Napa above water is the riparian vegetation-restoration projects undertaken by voluntary assessment districts in the Rutherford and Oakville upstream reaches of Napa River and the Army Corps of Engineers' Napa River-Napa Creek Flood Protection Project.

“Vineyards are not prevented from flooding, but conscious design mitigates flood damage,” Gamble said. “The health of the river is also improved with widening corridors for wildlife, and with the removal of barriers, including the redesign of some public bridges, salmon are spawning this year as far north as Calistoga.”

County and farming officials in the North Coast continue to assess flooding damage so far. But one big relief from the deluges is less anxiety over drought, according to Jennifer Putnam, executive director of the Napa Valley Grapegrowers trade group.

“We're a community of people, and there is a feeling of relief after four years of drought is so palatable,” Putnam said. “It's so nice to be not so stressed about water.”

BREATHLESS AND ROTTEN

Big concerns from wet vine feet are whether the vine roots can are starved of oxygen when under water or left susceptible to fungal infections, said John Bacigalupi, co-owner of Bacigalupi Vineyards. Rows of pinot noir in the family's 60-acre Frost Ranch vineyard were under water when the Russian River went well above flood stage early this month. The Bacigalupis bought the property in 1993, and the same part of the vineyard was under 8 feet of water during the 2005 flood.

“The vines come right through it, if the soils drain well,” he said. “They can stand it when they are dormant, and some rootstocks are more tolerant of wet feet.”

The soils in that section of the vineyard are dominated by sands and gravel, which drain standing water much faster than heavy-clay soils. Just after the fall harvest, he and other growers await the first frost to coax the vines into dropping the remainder of their leaves and slow their need for oxygen and nutrients.

Last week, Bacigalupi's three-person year-round crew was out in the rain prepruning vine canes to help stave off infection from the Eutypa fungal disease until final pruning work just before the vines awaken.

While vine physiology can tolerate wet feet for a while during dormancy, once the vines start growing again as the days lengthen and warm, wet feet can become a problem, Bevill said.

“If it happens late in spring where we start to see buds swell and grow just prior to growth, the roots start to suffocate at that time of year, if there's standing water,” he said. “You can create the same problem if you overirrigate in spring and in summertime. In spring, you want soils without soggy, wet ground.”

But all the water in the vineyard also can help with pest control, filling the burrows of critters that munch on the vine roots, Bevill said.

RUN ON THE BANKS

While rivers have carried the rich, deep soils that have created North Coast appellations of world renown, there can be too much of a good thing when water eats into and flows over the banks. An area famous for its share of major soil deposits and withdrawls is the section of the Russian River north of the Alexander Valley Road Bridge, Bevill said.

“Years ago there was 3 to 4 feet of silt put on fields above the bridge,” he said. “One grower had to use Carry-Alls running up and down the street to move thousands of yards of fine silt deposited in vineyard. It had raised the level of the soil in the vineyard.”

Jeff Quackenbush (jquackenbush@busjrnl.com, 707-521-4256) covers construction, commercial real estate and wine.