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Scientists Study Effect Of Rainier Glacier Melt

MT. RAINIER NATIONAL PARK, WA (AP) - A slurry of rocks and mud sounded like a freight train when it ripped through a popular Mount Rainier hiking destination in 2001 and scared some television viewers who believed their homes were in the path.

As it turned out, the debris flow at Comet Falls proved less dangerous than initially believed, but it gave scientists insights into a phenomenon that continues to mystify.

Such a debris flow likely added damage to Mount Rainier National Park when a flood sparked by nearly 18 inches of rain in two days shut it down in November 2006. Experts are concerned that the level of flood danger is increasing as sediment builds in glacier-fed waters like the Nisqually River.

Scientists suspect that climate change - specifically, shrinking glaciers that leave unstable rock behind - is adding to the risk of debris flows that help clog river channels downstream.

This summer, a team of researchers is gathering information at Mount Rainier that could help provide answers. One of the leading scientists is Gordon Grant, a U.S. Forest Service hydrologist and Oregon State University professor of geosciences.

“ Geological record documents debris flows for as long as the mountains have been around,” Grant said. “But given well-documented glacier retreat here and elsewhere, now is a good time to ask whether glacial retreat is changing the risk.”

Among the scientists’ questions: Have debris flows become more frequent? Does this add to the dangers around the Nisqually River and Mount Rainier’s other glacier-fed rivers, making them more likely to jump their banks?

Consider this: At Longmire, the river is nearly 30 feet higher than most of the national park compound, including the popular National Park Inn, ranger housing, maintenance shops and other historically important buildings.

Glaciers on Mount Rainier and elsewhere are shrinking, and glaciologists have blamed climate change. Debris flows typically begin where glaciers run out.

Moreover, sediment has been building up to a foot per decade on the bottoms of rivers such as the Nisqually, increasing the likelihood of future floods.

The process, which river experts call aggradation, is typical of glacier-fed rivers of this type.

But Scott Beason, a Mount Rainier National Park ranger who measured the river beds before and after the flood and wrote his master’s thesis about them, suspects that climate change has added to the risk of debris flows which help clog the channels.

During the 2006 flood, Beason used a real-time Internet connection to monitor a U.S. Geological Survey gauge in the Nisqually River. He noticed that water lines didn’t rise smoothly. Instead the picture was interrupted by spikes, small jags representing pulses of debris, rather than water, which boosted the flow.

“ The power of water to sculpt the land is just amazing,” Beason said. “It doesn’t take much to start a debris flow. They’re just a completely different kind of monster than a river.”

In 2001, scientists Carolyn Driedger and fellow U.S. Geological Survey volcano experts went up in a helicopter to check on reports of the debris flow at Comet Falls.

Driedger and her colleagues got a look the following day, when a second mass cut loose. “It was one of the most spectacular things I’ve ever seen in my whole life,” Driedger said.

A 6-foot-wide stream of melt water slipped out of one glacier basin and into another, then became a muddy slurry that bulked up as it enveloped a mass of rocky refuse and charged downhill.

Before that helicopter flight, few scientists had observed the birth of such flows.

The Comet Falls incident took place in summer and was unrelated to flooding. Even so, Grant suspects a link between debris flows and floods is common to volcanoes throughout the Pacific Northwest. “It’s a coupled phenomenon,” he said, meaning that volcanic debris flows are frequently associated with floods.

One theory is that climate change has increased the incidence of extreme storms. Scientists plan to look for a correlation between bad weather and debris flows, Grant said.

Also, Grant said his team plans to take a closer look at how debris flows come about. ”We don’t really know the mechanism by which they begin,” he said. “A key issue is how they bulk up.”

The same November 2006 storm that closed Mount Rainier National Park also wrought big changes on Oregon’s Mount Jefferson and, perhaps more significantly, Mount Hood, Grant said. Highway 35, the only access road to Mount Hood Meadows Ski Resort, was cut off for two weeks because boulders and mud washed out the highway in some places and buried it in others.

On Mount Hood, this kind of flood damage has become almost routine, said Paul Kennard, a National Park Service geomorphologist, or scientist who studies natural processes shaping landscape. Kennard, whose specialty is rivers, believes it’s only a matter of time before Rainier’s road systems suffer the same fate.

“ Mount Hood is the future for us,” he told rangers during a recent park training session.

The way gravel and sediment have choked up the Nisqually and other park rivers astounds him.

Where the stones come from isn’t a secret. Between 2,000 and 7,000 feet above sea level, Mount Rainier is “a barrow pit of loose volcanic rock,” Driedger said. “That’s fine until we get increased stream flow for one reason or another..”

Geologists have come to expect debris flows on the flanks of volcanoes such as Mount Rainier. They occur when glaciers retreat or pull back from areas where they once buttressed huge piles of stones, Driedger said.

But before the Comet Falls, debris flows were followed up in 2003 and 2005 by similar incidents at Christine Falls, adjacent to the road between Longmire and Paradise.

The worst debris flow in park history took place in October 1947, when two days of heavy rain eroded the end of the Kautz Glacier. The result: 28 feet of debris buried the Nisqually-Longmire road and Kautz Creek, another Nisqually River tributary. If park visitors know where to look, they can still see the remains of trees buried by the 1947 debris.

This summer, Beth Copeland, an Oregon State graduate student working with Grant, will begin to review the maps and other records on Rainier’s past debris flows.

Much of it has been a focus of previous study, but perhaps not with climate change in mind, Grant said.

While Copeland is at work inside the park, climatologist Anne Nolin, an Oregon State associate professor, will scrutinize past weather patterns, Grant said.

People might like to blame the November 2006 flood on climate change, but no single event tells the tale, Grant said. In that sense, Hurricane Katrina is analogous, he said.

“ It’s very tempting to wave the climate change flag, but we really don’t know yet,” Grant said.

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