Owners of private lands within the burn areas for the Atlas, Nuns and Tubbs wildfires face a new task now that the fires are largely extinguished – helping their properties recover.
Fire-burnt trees near roads or house sites might be dead and pose safety hazards because they might fall. Plastic pipe culverts for road crossings over streams might be melted. Scorched vines might be either in good shape or seriously damaged.
Speakers at Wednesday’s Napa Valley Vineyard Technical Group meeting gave tips on how owners can deal with situations that will vary property-by-property.
“There are going to be days when you feel like you’re making it up as you go along,” said Greg Giusti, a UC Cooperative Extension emeritus. “You are. You haven’t done this before.”
Giusti talked about forest health and recovery strategies. The Atlas, Nuns and Tubbs fires burned 145,000 acres in three counties. A conservative estimate of 100 trees per acre yields an estimated 14.5 million trees potentially affected by fire, he said.
Trees can be killed by either flame or heat. Radiant heat is a problem for trees that were near burning structures, cars, tractors or other objects, he said. These trees may have been exposed to intense, localized heat for a long period.
A tree killed by radiant heat might still have green leaves or needles, Giusti said. He told how to chip at the bark to look at the cambium layer that should be white, with watery resin.
If this layer looks like maple syrup, it’s been cooked, he said. The color is brown.
“Ten years from now, there’s still going to be dead trees standing out there,” Giusti said. “Over 145,000 acres, not every tree is going to be addressed. Your landscape in Napa County will have fire scars out there for a long time.”
Phill Blake, who is retired from the United States Department of Agriculture, talked about erosion and about runoff in small, seasonal gullies in burned areas.
Post-wildfire storms can result in higher-than-average runoff, he said. For one thing, there might be fewer trees in the watershed to intercept rainfall.
“Keep in mind your average runoff, erosion potential, sedimentation, is going to be pretty intense,” he said.
He showed a photograph of steep, burned slope near a farm pond. The potential exists for ash to run into the pond during storms. He suggested diverting runoff from this bare slope around the pond.
“This ash material when it’s mobilized is very slick, gooey stuff and difficult to filter with your filtration systems, obviously,” Blake said.
A USDA brochure recommends installing sediment control measures on burned properties, such as straw wattles, mulch, plantings and sediment traps. It recommends consulting with a resource conservation district – locally there is the Napa County Resource Conservation District.
In other cases, the best solution might be to do nothing and let nature heal the soils and vegetation, especially in wildland areas, it said. Tampering might even delay recovery.
A storm forecast to start Thursday could drop an inch or more of rain on Napa County over several days, a Napa County press release said. Much of this rain is likely to soak into the ground and large debris flows are not expected. Small amounts of ash may get into local streams and reservoirs, but not enough to cause health concerns, it said.
Meanwhile, the county continues to work with local cities on erosion prevention steps near public reservoirs and public roads, the press release said.
Andrew McElrone of the USDA talked about assessing the health of singed or burned vineyards. Damage can range from none to so severe that vines require replanting.
“Depending on the degree of damage, the vines can fully recover,” McElrone said. “They’re pretty resilient.”