Leslee Riddell’s cabin in Orange County’s Holy Jim Canyon was one of just seven to survive the Airport fire in September. Now, she’s doing everything she can to prepare the historic structure from the threats that winter storms and newly burned hills can bring: Floods, debris flows and mudslides.
Thirty-four cabins were destroyed in the wildfire. Riddell’s cabin is nestled in the Cleveland National Forest only a few miles from where the blaze began, and sits at the bottom of a potentially slippery, 1,000-foot canyon wall, making it particularly vulnerable.
“Everyone seems to think that our backyard is probably the worst of all as far as if there’s mud and debris and water flowing off the canyon walls… the soil is very loose and it won’t retain water because it’s been burnt. So, whatever’s up there, that can come down, it will come down,” Riddell said.
Similar threats loom over those living near burn scars from the other big Southern California wildfires this fall, including the Line fire in Riverside and San Bernardino counties, the Bridge fire in the Angeles National Forest and most recently, the Mountain fire in Ventura County in November.
“There is a very high concern that when we finally do get our big storm with some pretty intense rainfall then there is definitely a threat of mud and debris flows for all the major burn scars, said Peter Thompson, a meteorologist with the National Weather Service. “They’re at the top of our attention for any upcoming winter storms over the next several months.”
Normally trees and other vegetation help soak in rainfall. But when all that is burned by a wildfire, not only does the ground lose the erosion-preventing vegetation, the ground actually becomes hydrophobic – water-hating.
“Every raindrop that wants to fall pretty much can just start sliding downhill. When you have a lot of it focused in a short amount of time, you can start thinking about debris flow and ash and landslide concerns,” David Munyon, another NWS meteorologist, said.
First-year burn scars are particularly susceptible to debris flows due to the lack of vegetation and fine, loose, and hydrophobic material present in the freshly charred soil. Areas downhill or downstream of wildfire burn scars are at an increased risk of flash flooding and debris flow, especially steeply sloped spots.
Wildfires have burned over a million acres in Southern California this year, according to CalFire.
On September 5, the Line fire started and scorched over 43,000 acres in the San Bernardino National Forest. Arson was found to be the cause.
Three days later, on September 8, the Bridge fire began and ended up burning more than 56,000 acres in the San Gabriel Mountains stretching across both LA and San Bernardino counties. The cause of the Bridge fire is under investigation.
On September 9, the Airport fire, which was sparked by an Orange County public works crew, burned over 23,500 acres in the Cleveland National Forest in Orange and Riverside counties.
The federally led Burned Area Emergency Response team and the state’s Watershed Emergency Response Team projected that residents in Orange County canyon areas are likely to be evacuated at some point during this rainy season.
On Nov. 6, the Mountain fire broke out in Ventura County’s western Santa Susana Mountains and incinerated almost 20,000 acres. The cause is under investigation.
People living at the base of hills and mountains with burn scars are most at risk for mudslides and debris flows.
Riddell took a proactive approach in preparing her vulnerable cabin for future rain storms. In addition to acquiring dozens of sandbags, she and her husband bought barriers and had them installed along the cabin’s perimeter that faces the steep burn-scarred slope. Helping them was Team Rubicon, a veteran-led nonprofit organization helping communities with disaster prevention and relief. Orange County’s Airport Fire recovery manager connected Riddell with the nonprofit to help her come up with a plan to help prevent mudflow damage to her cabin.
“All of that should help mitigate it but we just don’t know, we have no idea … And the worst thing that could happen is there’s a big huge boulder up there that comes loose. It gets enough momentum from coming down, it comes off this wall, hits the barriers and goes straight into my canyon cabin and knocks a huge hole in it. I mean, that’s conceivable, it could happen,” Riddell said.
In 2005, a Silverado Canyon teenager was killed when a large boulder plowed through her room during a rock slide.
Preparing for a storm
Unsure if you live in a mudslide-prone zone?
“If you’re in any of the foothills where you have a hillside rising above you, and that area has been affected by a recent vegetation fire, err on the side of caution and assume that you are in one of those zones,” Orange County Fire Authority Capt. Greg Barta said.
Strategically placing sandbags around one’s property can help prevent flood damage. “Most of our problems are when water builds up along the edges of a structure,” said San Bernardino County Fire Department’s Battalion Chief Mike Wakoski in a Youtube video.
But, he added, “Never place sandbags on the outer wall of a building.”
Water absorbs through sandbags, builds up, and can seep into the structure. Instead, Wakoski said, place sandbags around doors and foundations. The goal is to have water run down and past the wall.
California’s Department of Water Resources created a video on how to effectively use and place sandbags. Cal Fire/Riverside County Fire Capt. John Clingingsmith Jr. said sandbags should be filled halfway to two-thirds full. When placing sandbags in a row, they should be slightly overlapping, and subsequent rows on top should be placed in a staggered fashion.
But even sandbags won’t do much to divert large mudslides and powerful debris flows, according to Jayme Laber, a hydrologist with the NWS.
“Sandbags are limited in their ability to stop water,” Laber said. “If it’s any significant flow at all, sandbags probably are not the best technique.”
“The most effective thing is to make sure you have awareness if you are at risk, and be aware if local officials are communicating that to you, and then stay informed by having multiple ways to receive warnings and watches and stay cued to the weather,” said Rose Schoenfeld, a meteorologist with the NWS. That includes checking weather.gov. She also advises that residents clear out their storm drains.
No one should attempt to walk or drive through floodwaters. Instead, safety get to higher grounds and call authorities, authorities say.
“If you start seeing on the news that there’s an atmospheric river coming or something like that and you’re kind of downhill or downstream of a burn scar, things to keep in mind (include) that there could be more than just water coming down,” Munyon said.
Those living in a flood- or mudslide-prone zone should have an evacuation plan, authorities say, including a grab-and-go bag packed with important items such as medicine, photos, credit cards, cash, water, snacks, and other items.
Don’t forget to pack a bag for pets, too.
Where to get alerts, sandbags
Residents can sign up for San Bernardino County’s local Alert & Warning System programs.
Sand and sandbags are available to San Bernardino County residents at no charge at a number of fire stations and other sites. Residents should call ahead to ensure supply availability and should bring a shovel in case personnel aren’t available to assist with filling sandbags.
LA County residents can sign up for Alert LA County to receive emergency alerts via text, email, and/or phone call.
Free and ready-to-fill sandbags and sand are available at more than 30 fire stations across the city of Los Angeles. LA County residents can find free sand and sandbag distribution sites through the county’s interactive map. Residents may be asked for proof of residency and are advised to call the fire station/location to ensure the availability of supplies.
Empty sandbags are available for Riverside County residents at all county fire stations. Some stations have a small supply of sand available, which is replenished when rains are expected. A limited amount of free sand is also available at the Riverside County Corporation Yard. Residents should call locations in advance.
Riverside County residents can sign up for emergency alert notifications via Alert RivCo.
Sandbags are available for Orange County residents to fill at a number of Orange County Fire Authority fire stations. Residents are encouraged to bring their own shovels.
OC residents can sign up for AlertOC and ReadyOC to receive local emergency alerts.
All fire stations throughout Ventura County will supply sandbags to residents, said Andrew Dowd, spokesman for the Ventura County Fire Department. He also advises Ventura County residents to check VCalert.org for potential evacuation orders and VCemergency.com for local information on significant storms.
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