Friday, April 23, 2010

Heavy rains lead to flooding concerns

Nearly an inch of rain fell in Castle Rock Fire area Wednesday

Express Staff Writer

Wednesday’s heavy rains created muddy, wet conditions along the rural road that heads west from Ketchum up the lengthy Warm Springs Creek drainage. Officials said the rains didn’t cause any mudslides to occur on surrounding slopes burned by the 2007 Castle Rock Fire. Photo by David N. Seelig

Since the Castle Rock Fire burned across the backcountry west of Ketchum in 2007, any time heavy rains hit the Wood River Valley, people's thoughts—especially those of local emergency services officials—turn to the possibility of large mudslides ripping off mountainsides out Warm Springs Creek.

On Thursday, the area appeared to have escaped the destructive, debris-filled mudslides that poured off open hillsides above Warm Springs Creek during previous rainstorms. That's all the more significant given that the National Weather Service measured 0.91 inches of rain at a remote weather station positioned within the fire area out Warm Springs Creek on Wednesday.

According to Travis Wyatt, a meteorologist at the National Weather Service office in Pocatello, the majority of that rain fell between 11 a.m. and 5 p.m.

"That's certainly an abnormal amount for this time of year," Wyatt said.

Around the valley, other weather stations also registered heavy rains on Wednesday. At Ohio Gulch in the mid-valley, 0.79 inches of rain fell, while 0.8 inches fell further south in Bellevue.

Despite post-fire mitigation work by the U.S. Forest Service in the lengthy Warm Springs drainage, landslides have disrupted traffic and the lives of rural residents in this outlying area nearly a half dozen times since the last embers cooled from the large, 48,500-acre fire area in September 2007.

Fortunately, no homes or lives have been lost, in part at least due to work by the Forest Service to stabilize slopes above the most threatened residential areas.

Recognizing the damage the recent storm could bring, the weather service at first issued a "flash flood watch" for the area, which it then upgraded to a "flash flood warning." The advisory expired in the early evening Wednesday.


Emergency officials said no slides were discovered in the Warm Springs area. That has led some to wonder if the danger of mudslides in the fire area is beginning to lessen.

Of course, one day of heavy rain doesn't match the extended stretch of rainfall the valley received in June 2009. Then, nearly six inches fell through the month, one of the highest recorded totals for any month in the Wood River Valley. The constant rainy weather, which followed wet weather that May, led to oversaturated and unstable slopes and, eventually, mudslides.

In addition to heavy rain and gusting winds of the past two days, the stormy weather also brought snow to the higher peaks surrounding the Wood River Valley. The National Weather Service was calling for between 2 and 6 inches of snow above 7,000 feet on Thursday. Those snows will help the region's meager snowpacks.

As of Thursday, snowpack in the Big Wood Basin was 62 percent of normal, nearly 10 percentage points below snowpack levels in recent weeks. Early spring snows in late March led to a partial improvement in local snowpack as the area heads into what is expected to be a dry summer.

The weather service predicts that the cool, rainy weather will end today, if only temporarily. In the Wood River Valley, temperatures are expected to reach the mid-50s today, with mostly sunny skies through Monday. A chance of showers is predicted from Tuesday through Thursday.

Jason Kauffman:

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