Officials closed part of Pacific Coast Highway on Sunday near where the Palisades fire burned as rain poured down and burn scar areas in Southern California were under a flood watch.

By Monday afternoon, it was clear the region had been spared any significant problems, but officials warned that Southern Californians will need to continue to be vigilant about mudslides and other problems when rains come again.

On social media Sunday, Caltrans said rain-caused mudflows in Topanga Canyon prompted the isolated closure of PCH west of Topanga Canyon Boulevard. On Monday morning, Topanga Canyon Boulevard was also closed in both directions due to debris caused by minor flooding.

As the rain continued, a National Weather Service flash flood warning was in effect for the Malibu area through 11 p.m. Sunday. The warning was for the Franklin fire burn scar and parts of the Palisades fire area. Such a warning means flooding has been reported or is imminent.

The “time of greatest concern” for elevated rain rates and/or thunderstorms was through 10 a.m. Monday, the weather service said on its website.

The Los Angeles Fire Department separately announced the closure of a stretch of Palisades Drive because of a mudflow.

Dozers were working to clear the area, and there was a closure at Sunset Boulevard and Palisades Drive.

Officials also responded to rocks in the roadway that gave vehicles flat tires around 7:07 p.m. in the area of Angeles Crest Highway and Gould Mesa Motorway in La Cañada Flintridge.

Caltrans responded to the scene and helped clear rocks from the road, according to the California Highway Patrol. No injuries were reported.

Officials said they regularly have to clear rocks from the road during floods. The CHP couldn’t immediately specify how many cars were affected or if they needed to be removed from the scene.

Also, the 5 Freeway in the Grapevine area, in the northern Los Angeles County/Kern County area, was subject to closures because of snow.

Assorted road closures were announced by agencies Sunday because of the fire and flood concerns, including Malibu Canyon Road between Piuma Road and Francisco Ranch Road.

And Monday, Caltrans announced the closure of all lanes of the 101 Freeway at the East Fourth Street off-ramp in Boyle Heights due to flooding.

The LAFD separately reported a mudflow in Woodland Hills at 4100 N. Alhama Drive, at Mulholland Drive. There were no injuries or rescues involved, but four vehicles were temporarily stuck in the mud, the department said. One was a fire agency pickup truck.

Meteorologists warned of floods as rain began Saturday and continued Sunday. While the rain can help alleviate dry conditions that helped fuel wildfires across the region, the hills can’t absorb water after vegetation has burned, leading to debris flows, flooding and mudslides.

Flood watches were issued from 4 p.m. Sunday until 4 p.m. Monday for areas affected by the Palisades and Franklin fires in Pacific Palisades and Malibu, the Eaton fire in Altadena and Pasadena, the Hughes fire around Lake Castaic and the Bridge fire in the Angeles National Forest north of Glendora.

While fire areas avoided major issues from the recent rain, the threat is not over.

“Residents in and around those areas will have to live with this ongoing threat of debris flows, flash floods, and mudslides for the next two years,” weather service meteorologist Ryan Kittel said.

Most fire areas take two years to recover before they are no longer considered a potential threat. Before that point, any storm could cause additional damage. Rainfall from regular storms seen once or twice a year could trigger mudslides or debris flow in burn-scar areas such as Altadena, where material can move down steep terrain and up against neighborhoods.

The intensity of the rain and the amount that falls within a short period of time can measure the potential scale of impact. Roughly half an inch per hour would be the starting threshold for concern, with the risk of “devastating” debris flows if rain rates reach over an inch per hour, Kittel said. December to March carries the greatest risk and gradually lowers into June.

In 2018, bursts of intense rainfall in burn-scar areas from the Thomas fire, which burned 281,893 acres in Ventura and Santa Barbara County, triggered a catastrophic mudslide in Montecito that swept homes from their foundations and killed 23 people total.

Staff writer Sydney Barragan contributed to this report.