The fall and rise of a creek’s fortunes

These days large swaths of the once-meandering Topanga Creek are dry and full of dirt and look like a Santa Monica Mountains hiking trail. The cause is a 1,000-foot-long berm that rises up to 30 feet high and disrupts the water’s 10-mile path to the ocean.

Beginning in the 1960s, residents fearful that heavy rains would swell the creek and flood their homes gradually began to pile on material to interrupt the water flow.

“If they had a contractor buddy who needed to get rid of cement, they’d say, ‘Bring it on here!’ ” said Suzanne Goode, a senior environmental scientist with the California Department of Parks and Recreation.

The creek, along Rodeo Grounds Road, is diverted off to a narrow path that causes it to slow down and dump its sediment. Water then trickles underground during the dry season.

On Monday, however, the parks department will begin a two-month project to remove 19,000 cubic yards -- weighing 26,000 tons -- of soil, asphalt, concrete and possibly car parts that form the berm so water can run year-round once again.

Dry weeds dot the sides of the berm. Below it lies the dusty creek bed and a rickety bridge that former residents once used to cross the creek.

Officials hope the restoration will give the federally endangered Southern California steelhead trout, a silvery gray-speckled fish 2 to 3 feet long, a chance to make a comeback.

About 60 years ago, roughly 1,500 steelhead trout traveled from the sea up the creek to spawn in the winter. Now, only about 10 swim Topanga Creek each year, and “those that show up are faced with barriers and bad habitat,” said Nica Knite, a Southern California manager with California Trout, a conservation group.

“Quite often they cannot get back downstream, and they’ll be trapped in pools that start to dry out,” Goode said.

A 2006 study by California Trout assessed the Santa Monica Mountains’ 23 watersheds and found that the restoration of Topanga Creek was one of three such projects needed to bring back a vigorous steelhead population, Knite said.

About 50,000 steelhead trout swam in waterways from the Santa Maria River to Baja California’s Domingo Creek as recently as the 1950s. Today, fewer than 500 swim in that area, she said.

These Southern California steelhead hold a special place in the evolutionary chain, with DNA that makes them descendants of the original species that appeared after the Ice Age melt, Knite said.

“They’re actually the first ones that evolved, and they are able to tolerate the warmer waters that we have in Southern California,” Goode said. “This is really significant because of climate change. The fish up north cannot tolerate the warm waters, so as northern streams become warmer, we may hold the key to having steelhead trout.”

Knite also said the Topanga Creek restoration will give scientists an opportunity to study how the southern trout adapts to changing habitats. She said that within a year or two, the effects of the berm’s removal will be evident. “Fish show up in places they haven’t been in years as soon as you give them a place to come,” Knite said.

The 1,600-acre parcel called Lower Topanga was acquired by the state parks department from the Los Angeles Athletic Club for about $40 million in 2000. In the process, the agency also became the landlord to a community of about 50 homes, the same community that decades earlier built the berm.

The state paid about $5 million to relocate the residents, Goode said. Buildings in the area were demolished over the last few years in preparation for the creek restoration.

The 12-acre project to remove the berm and some nonnative plants, and restore the riparian system with native plants, will cost about $3 million, Goode said.

Workers will plant willow, mule fat, alders, cottonwoods, sycamores and oaks, and remove the highly flammable and bamboo-like arundo plant, jacaranda, an orange tree and palm trees. Some nonnative plants will stay to address concerns of people living further up the canyon who don’t want vegetation uprooted.

“There’s exotic grasses, crab grass, fruit trees; it looks sort of like people’s backyards,” Goode said. “Then you have dry creek bed for thousands of feet that has these arundos growing on both sides instead of the willows that it should have.”

Residents were also concerned that some of the asphalt in the berm was probably dumped there after Lincoln Boulevard was repaved and might contain lead, Goode said.

Decades ago, when gasoline was still leaded, the lead would often drip onto the asphalt on roads or near gas stations, she said. Officials decided that all materials from the berm will be tested for lead. Lead-free dirt will be sent via a covered truck to a nearby dump. If any debris tests positive for lead, it will be trucked to a special landfill in the San Joaquin Valley.

The area will remain open to the public while workers restore it. The rainy season will probably bring water back to the creek later this year.

Officials envision a future in which the creek will run year-round and the area will look as it did in the 1920s and ‘30s. The bubbling creek would be free to choose its own path down the canyon’s crevices, full of silvery steelhead trout and other fish swimming back and forth from its headwaters to the Pacific. Around the creek lush green native plants will hopefully provide a thriving habitat.

“Restoring this area is the work of a lifetime,” said Goode, who is one of the managers on the restoration project. “It will not be done when I retire.”

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tami.abdollah@latimes.com