In scarred North Coast fire areas, atmospheric river raises risk of mudslides, flash floods

Inmates from Konocti's Cal Fire's California Department of Corrections fire crew clear fire damaged trees along Riebli Road and a tributary of Mark West Creek, Wednesday Nov. 15, 2017 near Santa Rosa, in anticipation of heavy rain. (Kent Porter / Press Democrat) 2017


Efforts to stabilize Sonoma County’s fire-scarred landscape against winter rains gained urgency Wednesday as a moisture-laden storm arrived in the region, raising the risk of mudslides, flash flooding and fallen trees.

The massive wildfires that swept through Wine Country in October torched nearly 140 squares miles of Sonoma County, baring huge patches of remote landscape and reducing whole neighborhoods to ash and rubble.

The fires were still burning when work crews began spraying some burned slopes with a slurry of seed and mulch to promote rapid vegetation growth. Elsewhere, straw-filled erosion-control wattles, sandbags and other barriers have been deployed to try to stabilize hillsides and contain runoff that may be contaminated by burned materials or carry sediment.

But much of the burned-over area remains at risk of debris or mudslides, particularly in the perimeter of the Tubbs fire, where the severity of the fire was most pronounced overall, according to early assessments.

Each fire footprint has steep, isolated areas where the threat of sliding rates high, with the largest such area in and around Hood Mountain Regional Park near Pythian Road and above Highway 12, according to post-fire hazard mapping.

Sonoma County watershed recovery coordinator Cordel Stillman said first-responders contacted a few residents in the area Wednesday to ensure they were aware of the incoming storm and were prepared to take precautions, if necessary.

Santa Rosa work crews also have been working feverishly to assess and repair 23 problem spots identified in Fountaingrove, where underground drainage lines and culverts have melted in some cases, and could cause slides or sinkholes in areas of saturated soil, Assistant Santa Rosa Fire Marshal Paul Lowenthal said.

Flyers were distributed several days earlier to more than 1,200 residents and businesses in the area, encouraging them to enroll in emergency notification systems and have emergency plans in place. But any evacuation “would be very localized, specific to the actual area of concern,” Lowenthal said.

City crews were planning to patrol the area through the night, monitoring the hillsides, but “none of the locations presents a significant public safety risk,” Lowenthal said.

The atmospheric river forecast by the National Weather Service was at least expected to be shorter in duration than most, lasting only until into the predawn hours today, followed mostly by light, scattered showers, meteorologists said.

Close to 2 inches of rain were expected in most urban areas by this morning, with 3 inches or more at higher elevations, including some of the mountainous terrain where recent wildfires stripped the vegetation from large ridgeline swaths, according to National Weather Service meteorologist Scott Rowe.

The weather service predicted bursts of rain descending at a rate of a half-inch per hour, potentially loosening exposed slopes and contributing to rapid accumulation of runoff. A flash flood watch was issued, but officials did not anticipate having to alert or scramble the public for any reason, Stillman said.

Cal Fire spokeswoman Suzanne Brady said she did not foresee serious ramifications.

“We just want people to keep their head on a swivel, be aware of their surroundings, looking around for what’s going on, and if they see something wrong, report it,” Brady said.

Out of caution, emergency plans were laid late Wednesday in the event of unexpected or isolated problems that put members of the public at risk, they said.

“Nobody really knows where the focus of the storm’s going to be until it gets here,” Lowenthal said. “Hopefully it doesn’t slide over the top of Santa Rosa and stall out. That would be the worst-case scenario.”

Even as the front edge of the storm arrived Wednesday morning, more than 500 people from multiple local, state and federals agencies, including inmate crews, were dispersed among an array of projects aimed largely at preventing debris slides and protecting watersheds from contamination, sedimentation and erosion, Brady said.

Task force personnel were “all over the place,” she said, clearing downed trees and branches from streams, installing erosion-control wattles on hillsides, and rooting out melted underground drainage pipelines.

Up in the Mark West Creek area, more than a dozen prisoners worked under the watchful eye of law enforcement officers Wednesday, used chain saws to chop up the tangle of charred tree trunks and limbs lying in and along a creek tributary.

As light rain fell across the area, the men and women from a Cal Fire crew inmate camp in Lake County hauled the debris out of the creek along Riebli Road and fed it into a roaring chipper. Brady said the chipped wood was being dispersed back on the charred soil to prevent slides.

A total of 252 inmates in 18 crews from around the state had been dispatched to watershed protection efforts, Brady said.

“The more people we have, the easier it is for us to mitigate the damage,” she said. “So they are very much appreciated.”

Crews also were deployed to two properties owned by the Sonoma County Agricultural Preservation and Open Space District and badly scorched by the fires, said Sheri Emerson, the district’s stewardship program manager.

The worst hit was a 1,000-acre property slated one day to be the Mark West Creek Regional Park and Preserve, where a barn and an older home were destroyed by the Tubbs fire, Emerson said. Some plastic culverts melted and need to be replaced, work for which regulatory agencies have granted emergency permits, she said. Mudslides also were a concern, as were debris-plugged culverts that might suddenly give way and cause flooding, she said.

Luckily, parts of the burned landscape already have shown signs of recovery. In the Calabasas Creek Preserve off Nuns Canyon Road, the grasses are returning and many trees have survived, Emerson said.

While the Douglas fir trees have suffered, many oaks, despite their blackened trunks, should be fine, she said.

“A lot of the oak trees are going to make it,” Emerson said. “They’re going to survive.”