Foothill communities get ready for mudflow threat

An intense rainstorm caused this catch basin in La Canada Flintridge, Calif., to fill up on Jan. 18, 2010.
An intense rainstorm caused this catch basin in La Canada Flintridge, Calif., to fill up on Jan. 18, 2010.
Molly Peterson/KPCC

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This week, Los Angeles County emergency teams are working to protect homes from heavy rains and mudslides in the foothill communities.

In La Canada Flintridge, KPCC's Molly Peterson talked with emergency responders and a foothill resident about the busy week ahead.

By mid-morning Monday, Pat DeChellis said the expected had become the actual: "Debris is starting to move out in the field," he said.

DeChellis, an official with L.A. County Public Works, says the big question this week will be how much mud will flow how fast. Officials expect the heaviest rain and mudflows Wednesday and Thursday. DeChellis says public works is keeping close tabs on the 28 debris basins in the burned areas – especially the smaller ones. "The fact is, though, we have a couple of our basins not designed for what we call our typical design event," he says. "Those are the hotspots."

Public Works crews have raised dams in some of those smaller debris basins, and used backhoes to dig out more capacity in others. But it's not safe to empty them when it's raining. "When there's a dry spell we can dewater the basin. We can try to get some of the material out. It all depends on the weather," DeChelllis says. "At some of the critical inlets, we have staff out there trying to ensure that they don't plug with debris."

That's exactly what Nalini Lasiewicz is worried about. She lives near the Pickens debris basin – one of seven that L.A. County Public Works plans to enlarge later this year. She works for Glendale Water and Power, whose engineers gave her some key advice: "If you hear a crack or a rumble get out. There's really no warning," she says.

All day Monday, Lasiewicz watched water mixed with ash, soil, and organic matter rumble into the Pickens debris basin for the second time. The first was in November. She made a video and took pictures. "It took the crews six weeks to clean it all out. And that was probably 40 percent of what I'm looking at now," she says. This morning, she could see to the bottom of the basin.

This afternoon, six hours later, it looked much more full.

Public works officials say they've planned well enough to capture debris brought down by all the storms this week. After watching sediment nearly fill the basin in six hours, Nahlini Lasiewicz is nervous. She's packed a bag and is ready to go, just in case county officials order evacuations in her neighborhood.

Watch Molly Peterson talk to Nahlini Lasiewicz near the Pickens Debris Basin here.