ENVIRONMENT : Flood-Control Measures Aid Burn Areas

Despite the torrents of rain that pounded the steep, fire-scarred slopes of the San Gabriel Mountains above Pasadena, the foothill communities of Altadena and Pasadena Glen remained virtually free of floods and mudslides.

Officials credit elaborate new flood-control measures, a healthy regrowth of hillside vegetation and sheer luck.

In Pasadena Glen, a culvert large enough to accommodate a truck channeled water and debris safely past homes. The $1.2-million culvert, funded with money from the Federal Emergency Management Agency and homeowner assessment fees, was built after a street was inundated last year with a knee-deep river of mud.

The mudflow caused enough concern among residents and county officials to prompt construction of the 10- by 20-foot culvert that would accommodate even the biggest boulders and swiftest floodwaters. A homeowners assessment contributed $500 per house the first year, an amount that will be smaller in subsequent years.

“This channel was built to withstand a 50-year flood,” said Steve Schindler, a Caltech astrophysicist and board member of the Pasadena Glen Community Assessment District.

Throughout last week and the beginning of this week, the 38-home Glen, known for its history of mudslides and rockslides, weathered the storm with nothing more than a few minor mudslides that spilled into some back yards.

“So far we really are doing quite well,” Williams said. “It’s very rewarding.”

That was the word through the rest of the burn area as well. Fire department workers installed sandbags and flood barriers to keep the rushing waters away from homes. Aside from a couple of soggy basements, workers said there were few problems with flooding.

Michael Minore, captain of Los Angeles County Fire Station 66 in Altadena, said vegetation that has grown since the fire held the soil with their roots. The plants also broke up the slick coating of oil and ash that covered the soil after the fire and which had kept rainfall from sinking in.

And finally, he said, “We didn’t have a real heavy downpour of rain.”

If the rain had been as intense as in some other areas of Southern California, he said, the area might not have fared so well.

Still, the area did receive about 3 1/2 inches during the first storm last week--enough that the lack of flooding is remarkable, said Stuart Seto of the National Weather Service.

“From our experience, this amount of rain should cause flooding,” he said. “So the credit ought to go to those people who set up those barriers and sandbags.”