Station Fire's accelerated flood cycle speeds public works planning for sediment management

The Station Fire burned nearly a year ago in and around the Angeles National Forest. The fire’s out, but the job’s not done for fire departments and public works crews. They’re still worried about what could happen below the burn area when a second rainy season arrives. Federal, state and local officials met to decide how to manage mudflows.

The mercury is nudging toward 90 degrees outside but at L.A. County Public Works headquarters, it’s cold and wet – at least, in video of winter floods. Mark Pestrella is a top watershed management engineer for public works, and he says the images are reminder of the truckloads of sediment – a hundred thousand or more – that washed down into debris basins when rain came down months after the Station Fire was out.

This year public works crews cleared 1.2 million yards of material. "In the long term we’re projecting something like 10-12 million yards of material that would end up in our debris basins through the course of time of course," Pestrella says. "That’s quite a bit of material."

Pestrella says fire and flood are a natural cycle in this region. L.A. County Public Works did plan for that cycle. But the Station Fire has accelerated and amplified its effects – starting at the steep, bare-burned areas in Angeles National Forest.

U.S. Forest Service manager Jody Noiron told city planners, scientists and engineers that a third of downstream water in L.A. County hits federal lands first. Those lands make up more than 70 percent of open space within Los Angeles County, so, says Noiron, federal land’s got a lot of local use overlapping on it.

"Even though we’re one of the smallest forests in the country, we administer more special use permits than any forest in the nation – approximately 2,000 permits," Noiron told a crowd of city managers, regional engineers and local officials. "As you folks know, because a lot of the stuff that’s up there is under permit to you!"

The L.A. County Flood Control District stretches from the foothills to the sea – and as many as 40 federal, state, county and city agencies have an interest in what happens there. Inevitably, that puts some officials at odds, says L.A. County’s Mark Pestrella. "These agencies, the regulatory agencies don’t always recognize that there’s overlapping regulation. And that’s become a roadblock," Pestrella says.

Say the county wants to restore habitat; a project might get easy approval from federal fish and game authorities, but regional water board staffers might say the restoration plans don’t go far enough. The head of L.A. County Public Works, Gail Farber, says it’s not just mudflows that agencies need to manage together. Stormwater flows to spreading grounds, dams and reservoirs – so protecting drinking water supplies is part of the puzzle, too.

Farber says the goal of this first meeting is simple: get everyone in the same room. "We want it to be a collaborative process so that we find balanced solutions that are economically sound as well as socially desirable, as well as environmentally sensitive," she says.

Farber says they’ll update the sediment management plan at meetings over the next year. It’s an urgent job. Accelerated debris flows mean that county facilities that were intended to hold the next 20 years of sediment could fill up in just five.