Tuesday, July 24, 2007

Flash floods threaten fire area

Posted: 7/24/2007

Fires and floods are the concerns associated with a round of potentially strong thunderstorms expected to surge across the area Tuesday.

A flash flood watch was issued for a region stretching from Lake Tahoe to Reno, Carson City and other parts of western Nevada and eastern California.

Of particular concern are those areas scorched by recent wildfires, including one that destroyed more than 250 homes near South Lake Tahoe last month and another that threatened hundreds of other homes last week on the outskirts of Reno.

“If any heavy rain falls on them you’ll get a lot more runoff, potential debris flows and flash flooding,” said Jim Wallmann, a meteorologist with the National Weather Service in Reno.

Monsoonal moisture, an unstable atmosphere and high temperatures are expected to combine to produce thunderstorms beginning noon today through the evening.
With the amount of moisture on tap, the thunderstorms could produce “a very heavy amount of rain,” beneath thunder cells, Wallmann said.

Heavy rain of up to an inch every half hour could fall in some locations, Wallmann said.

Officials will be on the watch for flash flooding problems at the scene of south Tahoe’s Angora Fire and at Reno’s Hawken Fire, which started July 16 at a Caughlin Ranch construction site.

“I don’t think it’s going to be too much of a problem but we’re definitely going to monitor the situation very closely,” said Marty Scheuerman, division chief with the Reno Fire Department. “We’ll be keeping an eye on it.”

The most potential for problems is along the Alum Creek drainage, which was “pretty well burned out” by the fire, Scheuerman said.

On Monday, experts from the U.S. Forest Service, Washoe County and Reno began the process of examining the 2,700-acre Hawken burn area to identify emergency rehabilitation efforts needed to avoid short-term erosion problems.

“They’re out on the ground looking at the situation — what burned, what didn’t. Where is there vegetation, where there is not,” said Gary Schiff, district ranger with the U.S. Forest Service.

If today’s expected thunderstorms don’t cause many problems in the way of flooding, they could still produce plenty of lightning that could start new fires, Scheuerman said.

Heavy rain could help extinguish lightning-sparked fires located directly beneath thunder cells but lightning strikes could hit the ground up to a mile away from those cells where rain doesn’t fall, Scheuerman said.

Strong and erratic winds caused by thunderstorms could cause any fires that do start to spread quickly across a kiln-dry landscape.

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