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Flood warning keeping area on alert

Cooper Landing, Moose Pass watch rainfall, await rupture of Snow River ice dam

Posted: Friday, August 31, 2001

Rain is falling and the rivers are rising: It's that time of year in the upper Kenai River basin. This year, the added suspense is the pending rupture of the Snow River Glacier Dammed Lake.

The National Weather Service issued a flood warning Thursday predicting the Kenai River at Cooper Landing would crest late this afternoon about a foot above flood stage. Rain in the Kenai Mountains sent streams surging earlier in the week. Areas affected by high water include the Snow River at the south end of Kenai Lake, Trail Creek near Moose Pass, the Primrose Campground on the shore of Kenai Lake and, possibly, the Kenai Keys subdivision east of Sterling.

But rainfall in the area should slack off, and residents in the Cooper Landing area have their fingers crossed that the water will start falling today.

"It's business as usual," Gary Galbraith, owner and operator of Alaska Rivers Company, said Thursday.

The high water has discouraged anglers, but his company is still taking clients out to raft the river. If people are cautious and wear personal flotation devices on the water, they should have no trouble, he said.

"We'll be running as usual. It is just the water is high. That's normal this time of year."

About noon Thursday, the Kenai River reached the official flood stage of 13 feet on the gauge by the bridge at the river's start in Cooper Landing.

Much of that water comes from the Snow River, Galbraith said.

"The Snow River cresting is always good for us."

The Snow crested Tuesday afternoon, according to flow gauge information the U.S. Geological Survey posts on the Internet. Its water has gone down slightly, but remains almost 3 feet higher than it was a week ago.

At the end of June, the upper river reached similar heights. That was an unusual occurrence due to heavy snowmelt in the mountains. The current high water is a normal effect of seasonal rainfall.

The situation could change if rains grow heavy or the glacier dam gives way when the river is already running high.

At the top of the Snow Glacier, at the headwaters of the Snow River north of Seward, an intermittent lake formed behind the glacier is growing. Based on past cycles and the amount of water in it, the lake is expected to rupture and start draining into the Snow River at any time.

The National Weather Service's Alaska River Forecast Center is monitoring the lake's status, because the drainage could combine with rainfall to cause flooding.

Hydrologist Larry Rundquist explained that the expected "profile" of a flood from the glacier lake would be the opposite of that from rainfall.

The water will begin seeping from under the glacier slowly, then pick up volume and speed as it carves a bigger channel underneath the ice. When the lake empties, the water levels in the Snow River will abruptly return to normal, he said.

The lake drains every two or three years. It last drained in 1998 between Sept. 30 and Oct. 14.

When the lake begins to drain, the weather service will use computer models to predict the timing and level of potential flooding downstream.

Rundquist said the event is unlikely to cause flooding in the lower river because the effects dissipate as the water moves across Kenai and Skilak lakes and past major tributaries such as the Killey and Moose rivers.

The glacier lake could contribute to flooding in the Cooper Landing area, but residents would have days of notice.

To provide that vital notice, people are keeping a wary watch on the lake.

Cooper Landing pilot Lyman Nichols has volunteered to fly over the lake periodically and report on its condition to the weather service.

Bad weather kept him grounded much of the week, but Thursday afternoon he was able to get in the air.

"Every creek in the country is running high," he noted.

Although clouds blocked a view of the markings that show how deep the lake is, Nichols was able to scope out the general condition of the lake.

"The glacier is showing signs of cracking like it is lifting," he reported. "I could see (the lake) has not started going down. It's hanging in there.

"But it's getting close."



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