Endangered trout may soon return to the concrete Los Angeles River

Los Angeles — Flowing a few inches deep following a recent rain, the Los Angeles River looks more like a vast flooded interstate highway rather than any river found in nature. And yet it is the largest paved waterway in the world, best known as the filming site for car scenes in movies such as Grease and Terminator 2.

Hemmed in by towering concrete floodwalls, the urban river courses nearly 49 miles through Los Angeles County, from its headwaters in the Simi Hills and Santa Susana Mountains to its mouth in Long Beach. The river was left in a relatively natural state until 1938, when a disastrous flood breached its banks, killing 115 people and destroying 5,000 homes. Pressure quickly built on both the city and the federal government to take drastic action to contain the river.

Although this radical transformation protected human life and property, it also diminished a diverse riparian ecosystem that hosted spawning grounds for various aquatic species, including the southern California steelhead trout, which is now federally endangered. These days, the much-reduced river supports only the hardiest of species, most of them non-native, such as sunfish and carp.

But now, following decades of public frustration about the river’s poor condition, the city—in coordination with the state and federal agencies—has mobilized to restore the waterway and its habitats.

One of the most prominent pilot projects in the billion-dollar effort is the Los Angeles River Fish Passage and Habitat Structures Design Project, which aims to allow fish—especially steelhead—to move freely through the river once again.  

Like salmon, steelhead are anadromous fish that live in the ocean and return to rivers and streams to spawn. As recently as the early 1900s, steelhead in the tens of thousands would make the run from the Pacific Ocean upstream through the Los Angeles River to its mountain headwaters. Anglers would congregate at spots like Steelhead Park, now near Dodgers Stadium, hoping to catch these iridescent sportfish that can grow up to three feet long.

On a recent March morning, at the confluence of the Los Angeles River and a stream called the Arroyo Seco, a group of scientists peer into a lifeless-looking culvert that appears a very unlikely candidate for a future trout stream. The roaring Arroyo Seco Parkway passes overhead, with the river’s span further divided by a cluster of bridges and laced with power grid transmission lines. (Read how rivers and lakes are the most degraded ecosystems on Earth.)

However, even amid this heavily urban environment, Wendy Katagi, project manager from the environmental consulting group Stillwater Sciences, says she’s optimistic the steelhead will eventually return.

Katagi, whose group specializes in watershed restoration, explains how improving this channel and controlling its water flow will transform the channel.

“It sounds lofty, but based on the science, it is achievable,” she says as flocks of swallows and other birds chase back and forth between banks and bridges overhead.

Fish out of water

Following the Flood Control Act of 1941, a team of agencies led by the United States Corps of Engineers created new dams and encased the Los Angeles River’s natural course with concrete. The resulting channel’s hard, narrow bottom created currents far too strong for the steelhead, which immediately began to vanish.

The last steelhead was caught in 1948. In the ensuing years, fish populations crashed, and in 1997, the Southern California steelhead trout was listed as endangered. Their exact population is unknown, but a recent study documented only 177 individual sightings of southern California steelhead from 1994 to 2018.

You May Also Like

MAGAZINE

In a warming climate, we need to radically rethink how we conserve nature

ANIMALS

Is this paradise—or a parking lot? This Florida ecosystem is a battleground.

FAMILY

Save the sea otters! How cute critters can inspire kids to protect the ocean.

Steelhead contribute in multiple ways to their ecosystems, Matt Drenner, senior fisheries biologist at Stillwater Sciences, says in an email. Young trout serve as prey for some species, and migrating steelhead transport vital marine nutrients from the ocean into freshwater environments.

Many of the existing flood-control measures along the river, such as the built-up cement banks, will remain, but obstacles to fish passage will be removed or reconfigured. 

For instance, project engineers plan to deepen the central channel by two feet, and line it with a soft, natural bottom mostly consisting of sand, sediment, gravel, cobbles, and aquatic plants. The river’s flow will also be managed so that the speed of the water is slow enough to allow steelhead migration. (Read how hydropower has transformed most of the world’s rivers.)

Ultimately, the goal is to build a comprehensive passage for steelhead, complete with side pools and other habitats spanning the length of the river. Ideally, steelheads isolated in mountain headwaters will begin to return to the sea, helping to the species to recover. The first phase of the project should be completed by the end of this year.

“We don't doubt that if the [water] velocities are suitable for them to migrate, they'll do it,” says Katagi, whose design team is working in coordination with the city of Los Angeles, the United States Corps of Engineers, the Council for Watershed Health, and numerous other agencies and organizations. “It's an opportunistic species.”

Other animals would benefit as well. A Los Angeles River healthy enough to support steelhead would also be hospitable to other species of native fish, many likewise vulnerable or scarce, like the Santa Ana sucker and the Arroyo Chub, she says.

Redefining the river

However, some experts question the choice of the river as the best site for the ambitious project, given the fact that it runs through the nation’s second-most populous city.

“There are so many impacts reducing habitat quality in the L.A. River, it may be a better use of funds to work on restoring steelhead where there is a better dollar-to-fish ratio,” Sabrina Drill, natural resources advisor for Los Angeles County, said in an email.

For example, the Ventura River, the Santa Clara River, or even the San Gabriel River, which has a more extensive upper watershed spawning habitat, would be cheaper and thus more reasonable choices, Drill says.

But for many who have long advocated for a healthy Los Angeles River, the return of steelhead to the river would be a transformational event. (See beautiful photos of rivers around the world.)

“Having steelhead trout return to the Los Angeles River and to their ancestral spawning grounds is the true baseline for meaningful restoration,” says Michael Atkins, communications director for the nonprofit Friends of the Los Angeles River.

Back at the confluence of the Los Angeles River and the Arroyo Seco, water released from some point further up the Arroyo Seco suddenly begins to pour into the Los Angeles River, threatening to raise the water level.

As Katagi leads the group away, a neon green sports car drives down the ramp from the road above and onto the concrete bed of the flood channel. The driver then hops out and begins to take photos of his car.

Someday, the Los Angeles River may no longer attract car chase aficionados, but instead draw anglers and nature lovers hoping for a glimpse of silvery steelhead as they once again make their dramatic journey upstream.