LOS ANGELES — Showers were reported across parts of Southern California on Sunday, with the forecast suggesting that these sporadic rains would persist overnight. This rainfall raises concerns about the possibility of toxic ash runoff in regions that have recently been devastated by wildfires in the Los Angeles area.
Flood watches have been announced until 4 p.m. on Monday, particularly in burn areas linked to recent fires around the Pacific Palisades neighborhood, Altadena, and Castaic Lake, according to meteorologist Joe Sirard from the National Weather Service in Oxnard. Sirard mentioned that the freshly burned areas are highly vulnerable to swift runoff, noting that even minimal rainfall in a short period could pose significant risks. “This situation leads to a considerable threat of mudslides and debris flows once rainfall surpasses certain thresholds,” he explained.
As of Sunday afternoon, a segment of the Pacific Coast Highway in Los Angeles County was closed due to mudflows encountered in Topanga Canyon, according to the California Department of Transportation. A flood advisory was also in place for certain sections of Ventura County until Sunday evening, with meteorologists predicting snowfall in mountain areas.
There is a potential upside to the rain, which may aid firefighters who have been battling several wildfires following a long stretch of windy and dry conditions. Crews in Los Angeles County devoted a significant portion of the previous week to removing vegetation, stabilizing slopes, and reinforcing roadways in the areas affected by the Palisades and Eaton fires, catastrophes that left entire neighborhoods in ruins after igniting amid powerful winds on January 7.
The Palisades Fire, the most extensive of the blazes, has led to the destruction of thousands of homes and resulted in at least 11 fatalities. As of Sunday, it was reported to be 90% contained. Meanwhile, the Eaton Fire, which erupted near Altadena and has claimed at least 16 lives, was 98% contained.
The Hughes Fire, which began last week north of Los Angeles and prompted evacuation orders or warnings affecting over 50,000 residents, was reported as 95% contained by Sunday evening. In San Diego County, firefighting efforts also made strides against the smaller Border 2 Fire as it traversed a secluded section of the Otay Mountain Wilderness near the U.S.-Mexico border.
Most areas in the region are expected to receive approximately an inch (around 2.5 centimeters) of rain over the next few days. However, the National Weather Service cautioned about the risk of localized cloudbursts which could trigger mud and debris flows down hillsides. “The situation could become problematic if one of those showers stalls over a burn site, which could be sufficient to generate debris flows,” suggested Carol Smith, a meteorologist with the agency, on social media.
In response to the situation, Los Angeles Mayor Karen Bass declared an executive order last week to hasten cleanup activities and to minimize the environmental consequences stemming from fire-induced pollutants. Furthermore, the LA County supervisors approved an emergency motion aimed at installing flood-control systems and facilitating sediment removal in these fire-impacted zones.
Fire crews have been actively filling sandbags for residents, while county workers have been setting up barriers and clearing drainage systems and basins. Officials have highlighted the hazardous nature of the ash present in areas that have recently burned, noting its composition includes remnants of incinerated vehicles, electronics, batteries, building materials, paints, plastics, and various household items, which means it could also harbor pesticides, asbestos, and lead. Residents in these areas have been advised to use protective gear during cleanup efforts.
Heightened concerns surrounding potential debris flows after wildfires have been prevalent since the catastrophic events of 2018, when the community of Montecito suffered severe mudslides following rainfall on mountain slopes that had been stripped bare by a significant wildfire. The consequences of that event included damage to hundreds of homes and the tragic loss of 23 lives.
The recent rains appear set to break a near-record dry spell affecting Southern California, with reports indicating that much of the region has experienced less than 5% of its average rainfall for this period in the water year, which commenced on October 1. Currently, much of Southern California is classified as being in “extreme drought” or “severe drought,” as per the U.S. Drought Monitor.
