Chart, Videos Show L.A. River's Dramatic Rise in Water Levels

The Los Angeles River's water level rose dramatically as heavy rains from Tropical Storm Hilary lashed California.

Hilary made landfall in Mexico's Baja California Peninsula on Sunday before moving across the border.

The first tropical storm to hit California since 1939, Hilary was downgraded to a post-tropical cyclone early on Monday, though threats remain. The National Hurricane Center in Miami said "life-threatening and locally catastrophic flooding" is expected over parts of the southwestern United States on Monday.

Hilary has maximum sustained winds of 35 miles per hour and is located about 390 miles north of San Diego, moving north at 29 miles per hour, the center said in its latest advisory. It is expected to move quickly across Nevada on Monday.

Videos posted on social media showed the Los Angeles River, which usually flows at a trickle, raging after Hilary battered California on Sunday.

A chart from the National Weather Service shows the river's level at Tujunga Avenue reached 10.24 feet at one point on Sunday, before dropping down to just under 6 feet early Monday. The water level had been at 2 feet for the past week and the river floods at 13.9 feet.

"Due to the significant rainfall amounts in the Los Angeles area, the Los Angeles River did have flow in it, but it was all contained in the channel and is now receding," Jayme Laber, a hydrologist at the National Weather Service in Oxnard told Newsweek.

"The system worked as designed and no anticipated rises or flooding is expected in the near term because Tropical Cyclone Hilary has moved north of the area now."

People in Los Angeles also took to social media with videos of the raging river.

"My entire life here & I've never seen the LA river this full," Cicely Raposa wrote in a post on X, formerly Twitter, alongside a video captured in Studio City.

"The river is raging. For perspective, the water level is probably about halfway or two-thirds up the flood control bank from where it normally is," Jeff Klein posted on X alongside videos.

Colin Fenby posted a short clip on X showing two people jogging along the banks of the river. "Crazy joggers in the rain next to the swollen LA River in Tropical Storm Hilary - definitely not recommended behaviour," Fenby wrote.

Forecasters continue to warn of dangerous flash floods, with warnings remaining in effect in Los Angeles County until 8 a.m. local time.

"Another band of rain has lead [sic] to high rain rates in San Gabriel mountains and foothills, and expanding to the west to include West Hollywood, Beverly Hills and Burbank," the National Weather Service in Los Angeles wrote on X.

"Rates of 0.5-1.0 inch per hour, and dangerous and life threatening flash flooding is occurring."

Update 08/21/23, 10:40 a.m. ET: This article has been updated with comment from Jayme Laber.