Tuesday, May 24, 2011

America’s next disaster: Multiple floods in Western states as monster snowpacks melt

Daily Mail

It's been one long series of natural disasters this year - and now it looks like another is on the way.

The focus may soon be shifting from the epic flooding in the Mississippi Valley to Westwern states where enormous winter snows have piled up on mountain ranges.

More than 90 sites from Montana to New Mexico and California to Colorado have record snowpack totals on the ground for late May.


Unbelievable snow: It's late May and a vehicle faces 23 feet of snow at Rock Cut on Trail Ridge Road in Rocky Mountain National Park in Colorado
Unbelievable snow: It's late May and a vehicle
faces 23 feet of snow at Rock Cut on Trail Ridge Road

It's been one long series of natural disasters this year - and now it looks like another is on the way.

The focus may soon be shifting from the epic flooding in the Mississippi Valley to Westwern states where enormous winter snows have piled up on mountain ranges.

More than 90 sites from Montana to New Mexico and California to Colorado have record snowpack totals on the ground for late May.


This has been caused by a winter marked by blizzard and an unusually cold and wet spring.

Now there is a very real fear of localised flooding at those sites as the snowpacks melt under hotter, sunnier conditions in June.

A sudden thaw could mean millions of gallons of water rushing through river channels and narrow canyons.

Bob Struble, the director of emergency management for Routt County in north central Colorado, said: 'This could be a year to remember.

'All we can do is watch and wait.'

Early warning signs: After heaving rainfalls,
Montana was hit by floods this weekend and is
braced for more to come.
At risk in Routt County is Steamboat Springs, the county's largest town.
It sits about 30 miles from the headwaters of the Yampa River, a major tributary of the Colorado River that has 17ft of snow or more in parts of its watershed.

The last time the west was hit by serious flooding casued by mega-thaws was 1983.

Since then, however, several wide open areas that were hit have now been developed into towns.
In contrast to the floods on the Mississippi River, which is centred on one mighty waterway, the Western story is fragmented, with anxiety dispersed across dozens of large and small waterways that could surge individually or collectively, the New York Times reports.

In California, officials staged three days of flood training last week, running disaster scenarios filling sandbags and tying down tarp.

It shouldn't be like this: Ellen Sowers wades through
flood water along the South Fork of the Ogden River,
east of Huntsville, Utah
The state’s aging levee system has long been a source of concern, with fears of large-scale failures that could leave Sacramento, the state capital, vulnerable to a Hurricane Katrina-scale flood.

The worries are heightened this year by the deep snows in the Sierra Nevada, where some ski spots around Lake Tahoe saw more than 60ft this season.

At Flaming Gorge Reservoir on the Green River in Utah, federal managers have begun spilling water downstream in readiness for the rising waters.

In the Wasatch Mountains outside Salt Lake City, where the Alta Ski Resort still has about 200 inches of snow, cool temperatures have kept snowpacks from crossing what hydrologists call the isothermal barrier — 32 degrees Fahrenheit throughout the snowmass — which allows gradual melting from the bottom.

Last week alone there was three feet of snow.

In sparsely-populated Wyoming, emergency officials are worried about tiny communities that in many cases are far from help if rivers surge.

Almost every county is in a potential snow-melt flood zone, and relatively few residents have flood insurance.

Scary stuff: National Water and Climate Centre map

In Colorado's Routt County, the terrain itself has changed, with thousands of acres of dead pine trees on high mountain slopes.

The trees were killed by an infestation of beetles in recent years and no longer hold the soil as they once did, raising erosion concerns.

From Sacramento to Baggs in Wyoming, a town of about 600 people on the Little Snake River, 150 miles west of Cheyenne, looking upslope at the end of May and seeing lots of white is not the norm.

Floods kill more Americans than lightning, tornados or hurricanes in an average year, according to federal figures.

Flash floods, usually associated with summer downpours, like the one that killed more than 140 people in Big Thompson Canyon in Colorado in 1976, can come as if from nowhere.

Arthur Hinojosa, the chief of the Hydrology and Flood Operations Office with the California Department of Water Resources, said: 'It just takes one really sunny hot spell to get things running.

'And that’s where our concern lies.'

In Montana, the fear of flooding became a reality on Saturday when washed out roads in Billings caused the cancellation of scores of high school graduations and several fishermen by swelling rivers, meteorologists with the National Weather Service said.

Much of the eastern two-thirds of the state is dealing with flood warnings or actual flooding as a slow-moving storm dumped rain across the region for several days, in some areas as much as six inches since Thursday.

The stormy weather began to hit the region as the state braces for more possible flooding after harsh winter and late spring snow storms deepened mountain snowpack to levels nearly double their average levels.

The state has received about three times more rain than normal so far this year.

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