U.S. Forest Service study shows flooding possible

U.S. Forest Service study shows flooding possible

24 October 2009

published by www.pe.com

USA — Storms that hit the Sheep Fire burn area this winter could cause flooding that would force the closure of roads and a segment of a national hiking trail and prompt the U.S. Forest Service to curtail off-roading in the area.

Some dirt roads over Lytle Creek Ridge, a portion of the 2,600-mile Pacific Crest Trail between Lytle Creek and Wrightwood and the two-lane, paved Lone Pine Canyon Road that runs west through Swarthout Canyon into Wrightwood could be affected by such washouts, according to a Forest Service study.

The areas discussed in the study, which was completed earlier this month, are in the Sheep Fire area where more than 7,000 acres burned in August.

Officials from the San Bernardino National Forest will use the study to decide which steps to take to keep erosion to a minimum, forest spokesman John Miller said. Closures are one option under consideration.

Forest Service hydrologist Liz Schnackeneerg, who headed the study, said the research team made up of hydrologists, soil scientists, cartographers, biologists, botanists, an archeologist and an engineer, studied the burn area to determine the soil condition and find out what may still be living in it.

They used satellite photo images to compare the burn area before and after the fire. The images show where the fire burned hottest and caused the most damage to the soil.

The most troubling damage comes in the form of hydrophobic soil, which results in water being unable to penetrate the dirt and increases runoff during storms, Schnackeneerg said. The steeper the slope is, the greater the potential for problems in the downhill areas.

“Sometimes you really can’t do much,” Schnackeneerg said. “There’s not a lot you can do except to acknowledge that there is going to be a risk and coordinate and communicate that risk.”

A reservoir built in the 1940s near Lytle Creek also was cited in the report as a potential problem.

The fire damaged the timber used in the dam but firefighters placed sandbags in front of it to help keep it stable during the winter, Miller said.

The fire had little effect on wildlife, Schnackeneerg said. Animals fled the fire, then tend to adapt to the changes. Vegetation should return to the area in about three to five years, she said.

The Sheep Fire is considered contained but not controlled, but a fire crew was called in recently to extinguish a spot fire near a ranch in upper Lone Pine Valley, Miller said.

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