Station Fire Could Cause Erosion

La Canada (myFOXla.com) - While an army of firefighters battles the 250-square- mile Station Fire today, scientists and technicians are trying to map and quantify how much ash, mud and rock could pour out of the burned-out San Gabriel Mountains the next time heavy rains fall.

A U.S. Geological Survey Landslide Hazards team is using NASA satellite images to prepare a burn-severity map that will show probability, volume, and locations of likely debris flows and mudslides, said Sue Cannon, a USGS project manager in Golden, Colo.

"The San Gabriels have a significant history of debris flow activity after fires," Cannon said in a telephone interview. "There are so many humans at the base of the mountains who could be impacted. We want to do this quickly."

Hazard technicians plan today to start field-checking images they received from the earth-observing LANDSAT satellite on Tuesday, and they hope to have a final report and map ready for public safety agencies by next week, Cannon said.

Six years ago Cannon helped lead a team that prepared a similar report within weeks of the October 2003 Old and Grand Prix fires, which denuded a 40- mile mountain front from Upland, below the east San Gabriels, to Highland, below the San Bernardino Mountains.

The need for timely and accurate assessment of potential post-fire dangers was underscored on Christmas Day 2003, when torrential rains on burned watersheds unleashed flash floods and debris flows that killed 16 people -- including nine children -- in Waterman and Cable canyons.

Other mapping specialists working on the Station Fire and post-fire hazard studies include support technicians from Redlands-based ESRI, a producer of geographic information systems software used by the Defense Department in Iraq and Afghanistan, as well as by public safety and fire agencies in the United States.

"We have provided tech support for many of the cooperating agencies on the Station Fire," Russ Johnson, ESRI's director for public safety and homeland security programs, told City News Service. "We have provided them with USGS topographic base data for areas considered at risk.

"We will be providing the same kind of support for rehabilitation teams and burned area emergency response teams," Johnson said. "They will be able to extract from GIS (geographic information systems) imagery areas that have the most risk of debris flows and mudslides."

While the Station Fire continues burning east in wilderness areas of the Angeles National Forest, county flood control engineers are assessing the potential for post-fire mud flows from burned areas above densely populated hillside communities in La Canada Flintridge, La Crescenta and Tujunga, said Kerjon Lee, a spokesman for the Los Angeles County Department of Public Works.

Thousands of homes below the Station Fire burned areas are protected by flood control channels and basins, according to Public Works maps and records.

But many other homes built in the past 40 years may be at risk, said Doug Hamilton, an Irvine-based engineer and former consultant to the U.S. Army Corps of Engineers, which designed and built many of the flood control structures intended to protect Los Angeles from erosion disasters.

"My concern is the proximity of the fire along the edge of development that's built in the 70s, 80s and 90s," Hamilton said. "They've never seen a post-fire erosion event.

"I see these houses cut into the side of the mountain," Hamilton said. "They're built according to building code, but it's frightening to look at. If there's heavy rains, a lot of these houses are going to be difficult to protect."

The likelihood of heavy rains this fall and winter remains unclear, but local, state and federal agencies must plan for worst-case scenarios regardless of forecasts.

The El Nino pattern that sometimes serves as an accurate predictor for Southern California's winter rain season appears "weak to moderate" right now, which makes the forecast difficult to call, said Bill Patzert, a climatologist at the NASA Jet Propulsion Lab in La Canada-Flintridge.

"But all you need is a couple storms and it's a big mess," Patzert said. "Whatever we get in the way of rain, it's going to be a mess. The areas that burned, some of them hadn't burned in 40 to 60 years. One part hadn't burned in a hundred years. "

Sen. Barbara Boxer, D-Calif., Tuesday encouraged U.S. Agriculture Secretary Tom Vilsack to ensure the U.S. Forest Service focuses on erosion mitigation efforts in denuded watersheds before the advent of winter rains.

"Erosion from steep hillsides will threaten water quality and often cause mudslides that damage property downstream and can seriously exacerbate flooding, as debris, mud and rocks clog flood basins," Boxer wrote in a letter to Vilsack, whose department oversees the Forest Service.