The first assessment of the absorption risk from a January fire due to the season’s most powerful storm set to soak Southern California on Thursday was that both Palisard and Altadena burn areas in the Pacific Ocean were days and months This shows that the risk of debris flow has increased significantly. .
In San Gabriel Valley, Etonfire was scorching deadly and devastating roads – leveling over 9,400 structures, including many homes – state reports say heavy rain could cause heavy rain I pointed out that there can be high. .
In West Los Angeles, where the Palisade Fire began on January 7th, there is a greater risk of flooding and rock slipping than debris flows. However, reports issued by the California Department of Forestry and Fire Protection and California Department of Conservation have said that in both regions, fires have left a wide range of land, including many areas where there is a risk of serious additional damage over the coming years. It states.
The report serves as a blueprint for potential damages that could arise not only from this week’s rainy weather, but also from future storms.
“Don’t put your life in danger,” Los Angeles County manager Kathryn Berger said at a press conference Wednesday. “The Foothill community is risky… so don’t let your security down.”
As she said, rivers of the atmosphere moved into the area, lightly showering Southland. However, the National Weather Service said the heaviest rain zones are expected on Thursday, particularly in recent burn areas, with the risk of debris flowing and flooding in recent burn areas.
In a three-day storm, Palisade scars are expected to receive 3.35 inches of rain. Eton Scar, 5.08 inches. Bridge scratches, 5.27 inches. But what can put things at risk is not just how much rain the area receives, but how quickly it falls.
Experts say the risk of rain slipping down a burning hillside increases as the rain begins to drop at a rate of 0.5 inches per hour. The weather department says rainfall is expected to peak between 0.5 inches and an hour per hour in the most severe portion of the storm, expected between 2pm and 10pm on Thursday.
Recently burned areas are at risk of landslides in heavy rain, and the soil is no longer anchored by healthy vegetation. Worse, heat from the fire makes it difficult for the soil to absorb water, making the hillside vulnerable to erosion. This can cause mud, rocks, rapids of dead branches, houses within that path, or slopes in people’s paths.
Data compiled by the US Geological Survey shows that storms supplying a peak of 15 minutes of rainfall intensity of 1.57 inches per hour means that debris flows can range from 80% to 100% across the majority of the Eaton fire area .
At Pallisard, a storm that unleashes a peak of 0.94 inches per hour of 15 minutes of rainfall, resulting in a 60-80% chance of debris coming along the strip of Tuna Canyon Park above Temescal Canyon and Pallisard in the Pacific Ocean. It flows. USGS data shows that hillsides and parts of the Mandeville Canyon area over Malibu are even more at risk.
“Flood and debris flow can escalate very quickly with little warning,” said Ryan Kittel, a meteorologist with the National Weather Service in Oxnard.
Areas where debris flow and flood risk in the Eton Fire Zone are Alzada Drive in Altadena, houses near the waterway above the Los Flores Debris Basin, East Roma Alta Drive in Altadena, and Arcadia Foothols Includes houses along the Pasadena Glen. CAL Fire reports that it is located near the community, a home located downstream of the Sierra Madre Dam and a home located in Sierra Madre Foothills properties.
Above the Palisades Fire Footprint, Los Flores Canyon, Pena Canyon, Topanga Canyon, and parts of Palisade Drive, Temescal Canyon, Rustic Canyon, are at risk of the danger of wreckage flow. A flood risk is added for homes near sources of water that run down from burned areas.
Dark Canyon, Carbon Canyon, South of Los Flores Canyon, Piedra Gouda Canyon, Tuna Canyon, North of Topanga Canyon, Camino de Yataste, Santaynez Canyon, Rivas Canyon, Sullivan Canyon, Parisades Drive Drive Drive area and near the Summit There is a moderate risk of debris flow, the report says.
Los Angeles County officials say they worked to reduce the risk of flood impact after criticising Southern California officials for not being prepared before the historic fire.
The crew is in a hurry to clear up 154 basins designed to overturn mud, rock and other debris into the neighborhood. They also installed thousands of sand bags, K-rails and compost filter socks (a kind of balm) to prevent dangerous debris from flowing into storm drains or coming into the ocean.
In some areas, authorities plan to use roads to capture sediment due to the amount of tiles and ash still in the burns, according to Mark, LA County Public Works Director. ·Pestralla said.
LA County officials said they expect a stream of debris to hit several homes during the storm. Officials say they have already contacted residents whose home is next to the burning slope to warn of the risk. Evacuation orders in some communities, including Altadena and Malibu, could be on the horizon, officials said.
“There’s a fragile structure in this case,” Pestrala said. “If our predictions come true… there are certain vulnerable structures that are highly safe, meaning we can see debris hitting the back of our house.”
County officials say the area’s fragment basin is sufficient to handle mud, vegetation and other things that could flow through Heights during the Whirlwind. State reports show that while debris basins help reduce the risk of debris flow, the San Gabriel mountain has a history of overwhelmed structures.
During the storm that followed the 1980 pine forest fire, the home was flooded in Altadena when 11 inches of rain fell for 24 hours, overwhelming the Rubio Canyon flood basin. The basin capacity has since increased.
In 2010, after the station fired, the Marary Canyon fragment basin was covered during a storm, causing 40 homes to be damaged.
Last week’s series of storms brought only mild rain to the area, but authorities said a debris-filled Eaton Washdam basin would be enough. The crew then removed 150,000 cubic yards of mud, vegetation and rocks from the basin, giving them additional capabilities for the storm, Pestrella said.
One of the worst debris streams in modern California history came in January 2018 when a river of mud and rock flowed through Montecito, killing 23 people and destroying at least 130 homes. The area was burned a month ago by the Thomas fire. One of California’s most destructive records, its flames burned 282,000 acres in Ventura and Santa Barbara counties, destroying more than 1,000 structures.
A contribution to the severity of the Montecito debris flow was that government officials were unable to build a larger basin that could not be devastating or devastating. The report also found that Santa Barbara County failed to completely empty existing basins prior to disaster, significantly reducing its ability to catch debris.
“We have the ability to be as large as the storm we expect,” Pestralla said Wednesday, adding that the crew “we’ve been working 24/7, 7th week, carrying wreckages from these areas.” I did.
Times staff writer Grestohay contributed to this report.
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