Rainfall eases wildfires but spurs mudslide threats across southern California

Rain fell across parts of Southern California on Sunday, offering much-needed respite to firefighters battling wildfires but raising concerns over toxic ash runoff and mudslides in areas scorched by recent blazes.

Flood watches remain in effect until 4 pm Monday for burn areas near the Pacific Palisades, Altadena, and Castaic Lake, according to the National Weather Service (NWS). Meteorologist Joe Sirard warned that even small amounts of rain could trigger mud and debris flows in the fire-ravaged regions.

“All these fresh burns are very susceptible to rapid runoff,” Sirard said, cautioning that heavy rainfall could lead to dangerous conditions above critical thresholds.

Highway closures and emergency efforts

The rain has already caused mudflows in Topanga Canyon, prompting the closure of a portion of the Pacific Coast Highway in Los Angeles County. A flood advisory was also issued for parts of Ventura County, and forecasters anticipated snow in the mountains.

Los Angeles County fire crews have been working tirelessly to remove vegetation, stabilize slopes, and reinforce roads in areas devastated by the Palisades and Eaton fires. These efforts aim to mitigate further damage from post-fire hazards.

Wildfire containment progress

The Palisades Fire, the largest blaze that destroyed thousands of homes and claimed at least 11 lives, is now 90% contained. The Eaton Fire, which caused 16 fatalities near Altadena, has reached 98% containment. Meanwhile, the Hughes Fire, north of Los Angeles, is 95% contained after forcing over 50,000 people to evacuate.

In San Diego County, firefighters have made progress in containing the Border 2 Fire, which has been burning through the remote Otay Mountain Wilderness near the US-Mexico border.

Toxic runoff and environmental concerns

The rain may provide relief for firefighters but has heightened the risk of toxic ash runoff. Burn areas are laced with incinerated materials, including vehicles, electronics, batteries, and household items, which could lead to significant environmental and public health issues.

Los Angeles mayor Karen Bass issued an executive order last week to expedite cleanup efforts and mitigate fire-related pollutants. The LA County board of supervisors also approved emergency measures to install flood-control infrastructure and clear drainage systems in affected areas.

Residents are urged to wear protective gear while cleaning up ash, which contains harmful substances like pesticides, asbestos, plastics, and lead.

A history of mudslide devastation

Concerns about post-fire debris flows are especially high following the catastrophic Montecito mudslides of 2018. Heavy rain on fire-scorched slopes triggered deadly mudslides that killed 23 people and damaged hundreds of homes.

Southern California's drought crisis

The rain breaks a near-record dry streak in Southern California, where much of the region remains in "extreme" or "severe drought," according to the US Drought Monitor. Most of the area has received less than 5% of its average rainfall since the water year began on October 1, compounding the challenges for fire-ravaged communities.

While the rain offers hope for drought relief, its immediate impact on fire-scarred landscapes highlights the precarious balance between recovery and risk in the aftermath of Southern California’s devastating wildfires.