Yes, the Los Angeles River is dramatically full. But it’s just ‘doing its job’

When newspapers across the world wanted to visualize this week’s torrential California storms, they chose the same image: a shot of the brown, choppy waters of the Los Angeles River, seemingly about to fully swallow the trunks of local trees.

Photos and video of the river dominated the homepages of the New York Times, the Washington Post and even the Guardian. On Monday, “LA River” was trending on (formerly Twitter), with more dramatic videos of rising waters.

But as many Angelenos know, during periods of heavy rainfall, this is pretty much what the LA River is supposed to look like. Those trees seemingly drowning in the high waters? A lot of them are willows and cottonwoods, floodplain plants that spread their seeds through floodwater, as Jon Christensen of the Institute of the Environment and Sustainability at the University of California, Los Angeles, told me.

“As long as the river doesn’t go over its banks and flood the surrounding neighborhoods, this is the modern LA River doing its job,” Christensen said.

That’s not to say that the flooding isn’t a real concern, especially after record levels of rain, or back-to-back storms.

Jessica Henson, a landscape architect and planner with a decade of experience working on projects alongside the river, said that a few areas along the river did look like they were “getting close to the max they can handle” and were “close to or starting to slosh over their banks”.

But when I talked to Henson on Monday afternoon, she noted that the peak of the storm’s rainfall “has come and gone”, and that “most of the gauges on the river are starting to go down”, meaning that the most serious flood risk was also decreasing. Other parts of the 51-mile channel had been “hitting only around a third of its capacity or less”.

Related: California storms ease after record rainfall leaves threat of landslides

Some of the most dramatic video footage showed areas of the river in the Studio City neighborhood, where water was “up near the top of the bank”, said Mark Hanna, a water resource engineer who has worked on LA River projects for the past 20 years. But that’s an area of the river where water levels are regulated, he said, so water was being released into the channel only at the rate that the river could handle it.

California storms, Henson said, had caused some real disasters in Los Angeles, including mudslides that had damaged homes and forced evacuations. But the Los Angeles River was, at the moment, “doing its job really well” and “keeping a lot of people safe”, he added.

If you’re surprised to learn that Los Angeles has a river, you’re not alone: in dry years, the river can shrink to a trickle, and perhaps its most famous film depiction is a chase scene from Terminator 2, in which the riverbed is mostly sun-baked concrete.

Before the 1930s, the LA River was a wild, rambling thing, a river that both flooded periodically and radically changed its course across the region. As Los Angeles, fueled by Hollywood and real estate money, grew into a giant metropolis, officials decided its shifting, flooding course had to be contained. One of the turning points, Christensen said, was “the wettest day ever recorded” in Los Angeles, 2 March 1938, when rainfall caused major flooding that left more than 100 people dead and caused what he estimated would today be nearly $1bn in damages.

One result of that historic flood was what he called “a decades-long effort to control the LA River”, by confining it to its current bizarre, concrete-encased course, which often looks less like a natural river than a carefully monitored “flood channel”.

This “solution” to the LA River’s flooding remains controversial, and it’s certainly not very pretty to look at. Even on its best days, if you put out a casting call for “post-apocalyptic landscape”, the LA River would get the role.

As a flood risk reduction channel, allowing excess water to flow swiftly into the Pacific, the river appears to have succeeded in its work this week. Still, city planners and scientists remain concerned that increasingly ferocious storms will test the river’s limits.

LA’s flood control system “can handle multiple atmospheric rivers, as long as they have some spacing between them”, Dena O’Dell, a spokeswoman for the US army corps of engineers, told the Los Angeles Times on Monday. But if atmospheric rivers hit “back-to-back without a break, the system could be tested”.

Both Christensen and Henson flagged several areas of the river that have sharply lower water capacity, and that could be overwhelmed in heavier storms. One is in Frogtown, or Elysian Valley, a gentrifying neighborhood north of downtown Los Angeles, where the river is full of trees and vegetation, meaning that water flows through it more slowly. The flood-prone neighborhood got its nickname from the large number of toads that once filled the streets. Modest homes along this risky stretch of river are now on the market for $1m or more.

Another risky area is further to the north, in some sections of the river in the San Fernando Valley, which were engineered about a century ago to withstand a level of flooding expected only once every 50 years, Henson said: “What we’re seeing 1707303580 in the valley, in places like Woodland Hills, it’s 10 inches of rain, which is approaching the capacity of that system.” But for now, the river experts said, the waters were falling, and the post-flood cycle would continue.

“The trees seem to do fine,” Christensen said. “They’ll come out adorned with all kinds of trash, and it will really look terrible.” Then, “we’ll have a big cleanup in the spring and summer, and hopefully, life will go on.”

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