Slower than normal recovery of the watershed damaged by the Thomas fire means for several years Montecito residents will be at risk for a repeat of the flooding and debris flows that devastated the community in January, according to a combined report delivered May 1 to the Santa Barbara County Board of Supervisors.
“We’re experiencing very slow regrowth, unfortunately,” said Kevin Cooper, leader of the U.S. Forest Service’s Burn Area Emergency Response, or BAER, Team. “And it is the re-establishment of vegetation on those slopes which will help protect us from … future flooding events.”
Cooper blamed that on a dry winter and late rains, as well as soil damage from the wildfire.
“We’ve lost a lot of soil and there’s not great regrowth,” he said. “So this puts us in a position that we’re looking at a similar type of risk next winter when the rainstorms come again.
“We’re looking at a slow recovery — slower than normal,” he continued. “Normally, we’d see up to 50-, 60-, 70-percent groundcover by now. But because of the weather patterns and because of lack of rain, essentially, we’re not seeing great recovery. Five to 10 percent is what we see out there.”
Better recovery of the Whittier fire burn area’s north-facing slopes means less likelihood of flooding in the Santa Ynez Valley, and Cachuma Lake may suffer less siltation.
“I did look at the Whittier fire,” Cooper said. “That north slope has recovered significantly — 25- to 50-percent cover, which is much, much better than the Thomas fire, and so we’re looking at some reduction in the potential for flooding in that area.”
However, those living below the south-facing slopes burned by the Whittier fire also face potential debris flows and flooding due to slow vegetation regrowth.
“These kinds of slopes can still produce debris flow with intense enough rain, so we’re not out of the woods entirely,” Cooper said. “But it is in better shape than on the Thomas fire.”
Assessing the damage
The report was developed by combining evaluations conducted by Cal Fire’s Watershed Emergency Response Team, or WERT, and by the BAER Team, who fanned out to begin assessing watershed damage even as the Thomas fire was still burning westward from Ventura County.
Also contributing to the reports were the California Geological Survey, the State Department of Water Resources, California Water Boards, the California Division of Oil, Gas, and Geothermal Resources and the California Office of Emergency Services.
Together, representatives of the various agencies made up the Watershed Task Force, many of whom were in the Emergency Operations Center during and after the Thomas fire and 1/9 Debris Flow, said Rob Lewin, director of the County Office of Emergency Management.
Field investigators not only looked at impacts from the Thomas fire but, also, some aspects of the Whittier fire, the 1/9 Debris Flow, emergency preparations undertaken between the Thomas fire and debris flow and actions undertaken since the debris flow.
Tom Fayram, deputy director of water resources, said the team’s findings were crucial prior to the debris flow.
“They literally had days (to assess the situation), and they gave us valuable information,” Fayram said, leading to such preparations as the county’s efforts to clear debris basins prior to anticipated rainstorms.
“If those debris basins had not been cleaned out … the destruction would have been much more widespread,” said Jeremy Lancaster, senior geologist with the California Geological Survey, who praised County Flood Control for its efforts.
Members of the BAER Team looked at damage, the recovery potential and possible future risks both on and off Los Padres National Forest lands, while members of WERT assessed similar impacts mostly on private property.
“It’s a very rapid assessment,” said WERT leader Drew Coe. “Basically, it’s supposed to be used for emergency planning only.”
While their focus wasn’t identical, the teams examined such factors as damage to infrastructure, endangered species’ habitat and cultural resources, vegetation loss and soil burn severity to assess potential revegetation, the spread of invasive species, sedimentation, flooding, rock falls and debris flows as well as risks to life and property.
They also considered the history of wildfires dating back to 1913 and debris flows at least as far back as 1934.
The studies resulted in maps showing the location of “values at risk,” areas of potential debris flows, predicted debris yield, soil burn severity and even locations of peak rainfall bursts.
Everything learned from the assessments will be used to come up with methods of enhancing the area’s recovery and to prepare for future events.
Levin noted the task force hopes to have a new risk-assessment map completed sometime this summer.
A history of disasters
Lancaster said although a lot of material was removed in the 1/9 Debris Flow, a lot still remains on the hillsides that poses a threat to the urban areas below, and channels that were scoured out have been left with overly steep sides that will collapse back into the channel, recharging them with debris for future flooding events.
Lancaster said often experts say disasters like the 1/9 Debris Flow happen every thousand years, but he noted Santa Barbara County has a history of devastating wildfires and debris flows.
“You’ve had 63 fires since 1913 from Gaviota to the county line,” he said. “And many of these have been sort of the basis for post-fire floods causing debris flow.”
Lancaster said the Thomas fire burned about 22,000 acres just in the coastal plain, and fires can be expected to burn a similar amount in that area every 10 years.
“These are not infrequent events, these fires,” he said. “And if we compare the historic evidence of debris flows with sort of the maximum events in the state … you’re having these debris flows occur on engineering time scales. They’re not every thousand years when they’re damaging and destructive, and I think that’s important to note from a planning and flood control perspective.
“The 1/9 Debris Flow event is comparable to the maximum debris flows we’ve had in the state that have been documented and on the historic record,” he said, noting it was rated at the top magnitude of 7 on the debris flow scale.
“But we have to consider that even smaller events will damage and destroy homes and take lives,” he added.
Waiting on Mother Nature
Board Chairman and 1st District Supervisor Das Williams asked what kind of treatments could be used to increase the rate of revegetation, like hydromulching and seeding, and to reduce damage from flooding.
Cooper said hydromulching only works on slopes of less than a 60-percent grade, but most of the slopes in the Thomas fire burn area are between 60 and 100 percent, and only works for moderate rains.
He said if the Thomas burn area had been hydromulched prior to the Jan. 9 rainstorm, it would have “simply ended up in the ocean.”
Cooper said the problem with regrowth is not seeding, and the team believes there is plenty of seed on the slopes now, even though a lot of the soil has washed away.
“The limiting factor here is the soil moisture, I think that’s the real issue — when the moisture came and how much there is there,” he said, noting that hydroseeding mostly plants grasses, which provide a good fuel for future wildfires and increase the risk of introducing invasive species.
Williams asked if that meant there is no treatment that could be applied for erosion control.
“Unfortunately, for these slopes, that’s true,” Cooper said. “It would take watering daily, it would take all these things I think are impossible to do. Unfortunately, it’s hard to hear this for everybody, but in these cases we have to wait for Mother Nature to take its course.
“And beyond that, it’s moving people out of harm’s way,” he added. “Of course, that’s a different kind of treatment. But I don’t believe there is a slope treatment that would be effective under these conditions.”