Wednesday, November 28, 2007

Officials: Castle Rock Fire increased avalanche danger

Slopes that lost timber or sagebrush will have a greater chance of sliding


By JASON KAUFFMAN
Express Staff Writer

A snowmobile rests at the base of a large avalanche that slid in the Baker Creek drainage northwest of Ketchum last winter. Courtesy photo

Recreationists with a penchant for backcountry thrills have always had to play it safe when heading out onto the steep slopes that make the Wood River Valley such a premier winter playground.

For these diehard types—mainly skiers, snowboarders and snowmobilers—the spoils of the powder-covered mountains come with the threat of avalanches.

And never has this been more true than this winter, which local avalanche forecasters say will present an increased level of avalanche danger due to the effects of the massive Castle Rock Fire, which burned across a 48,520-acre area in the eastern Smoky Mountains. Areas that saw intense fire activity during the more than two-week-long conflagration include Greenhorn Gulch, the west- and south-facing slopes of 9,151-foot Bald Mountain, large portions of the Warm Springs Creek drainage, Adams Gulch and Fox Creek.

The fire, declared contained on Sept. 4, burned across a vast area west of state Highway 75 from just north of Hailey to just north of Fox Creek and from the city limits of Ketchum west almost to the Blaine County line. Not all lands within the 78-square-mile fire burned as the blaze jumped around in a mosaic-like pattern.

In those areas that did burn, recreationists will need to keep a sharp watch out for a host of new hazards, some of which will be difficult to see, said Janet Kellam, director of the Sawtooth National Forest Avalanche Center in Ketchum.

"Do not expect these slopes to have similar conditions as in past years," Kellam said. "It's a whole new ball game, and we anticipate an increase in avalanche danger in some burned areas."

Kellam said that while workers at the Sun Valley Resort do avalanche control inside the boundaries of the ski area to prevent snow from building up and causing dangerous situations during the winter, the same is not true within the much larger out-of-bounds areas of the Wood River Valley.

In those areas, Kellam said, the Castle Rock Fire thinned timbered ridgelines that once sheltered slopes from wind-drifted snow. She said the timber on these slopes also helped anchor the snowpack.

She said that another thing to consider is that many slopes that burned during the fire used to have dense timber that prevented easy skiing. She said these slopes will now be more accessible to skiers and snowmobiles and have become prime avalanche terrain.

Kellam said that while these slopes may seem alluring, recreationists need to be extra cautious.

"Don't let powder fever and new opportunities cloud your judgment," she said.

The same is true for sagebrush slopes burned during the fire, which are also more prone to avalanche danger, Kellam said.

"The key is to stay alert, marvel at Mother Nature, have all the fun you can, but don't become complacent and assume we live in a manicured park," she said.

Besides avalanches, Kellam said other dangers caused by the fire include downed trees hidden under the snow that can cause leg injuries on otherwise placid-looking slopes.

She said fire-weakened trees and the loss of soils and root anchors have produced a whole new crop of fallen trees. And while the remaining upright trees may appear solid from a distance, closer examination may show that there are many hollow and dead trees just waiting to tip over.

What this means is that a ski run of yesterday may have new obstacles and conditions the following day, Kellam said.

"With these tenuous trees and altered terrain, we will experience a continually changing landscape from day to day, even hour to hour in some of the burned areas," she said.

Snowmobilers trigger avalanche

Several snowmobilers riding in the mountains south of Smiley Creek Lodge on Thanksgiving Day triggered one of the first avalanches of the season, said Janet Kellam, director of the Sawtooth National Forest Avalanche Center in Ketchum.

While the avalanche report she received wasn't detailed, Kellam said she does know the large slide happened somewhere in the upper Salmon River basin. She said that could mean the Salmon River headwaters, the Vienna Mine area or the Beaver Creek area.

"They all have similar conditions," she said.

Kellam said the snowmobilers were at an elevation of about 9,500 feet, were being cautious and not highmarking, but were near or along a steep slope. She said the large slide was estimated at 300 to 400 feet wide.

The slide reportedly happened on a northeast-facing slope and was about three feet deep. Only one person was caught in the avalanche, but was able to ride out unharmed.

Kellam said the avalanche apparently happened in an upper elevation bowl that had additional wind-loaded snow on top of the older snowpack.

For anyone considering an outing in the backcountry of the Wood River Valley or the Sawtooth Mountains, she said the areas to be most cautious about are those at high elevations, wind-loaded and on slopes facing east, north or northwest. She said the longer those cool, shaded areas sit, the greater the chance that they'll slide when new snow arrives.

"It's setting the stage for the next snowfall."

In these areas, Kellam said skiers and snowmobilers should look for a combination of weak layers within the snowpack and loose, sugary snow on the surface.

"It won't be a supportive base for the next snowstorm."

For the latest avalanche forecast for the local area, go to www.avalanche.org/~svavctr/ or call 622-8027.




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