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Taku River reaches near-record levels

Glacier dam release crests at 44.19 feet

Posted: Tuesday, July 24, 2007

A glacier dam broke open this weekend during its annual release and dumped enough water into the Taku River that it reached its second highest level in the 20 years records have been kept.

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The glacier dam release, or jökulhlaup, from Lake No Lake near the Tulsequah Glacier over the Canadian boarder crested at 44.19 feet early Sunday at the U.S. Geological Survey stream-gauging station. The Tulsequah Glacier is about 45 miles northeast of downtown Juneau.

The only time the river has crested higher since the agency began tracking it occurred in 2004, when it reached 45.07 feet.

"It was larger than normal," said Aaron Jacobs, a National Weather Service meteorologist who was monitoring the river. "What made the situation worse is the river was already flowing pretty high because of the above average snowfall from this year."

The flood stage begins at 43 feet. Moderate flood stage begins at 44 feet, and major flood stage occurs at 45 feet.

At its peak flow, the Taku River was running around 110,000 cubic feet per second early Sunday. The average median flow for July 22 is 29,100 cfs, USGS Juneau Field Office Chief Dan Hess said.

"The base flow was higher and the outbreak happened, and it raised up around the 100,000 (cfs) mark, which is a pretty good flow," he said.

"It pretty much doubled from the flow prior to the outburst," Jacobs said of the release. "That's pretty significant just because of the amount of water going down."

Historic crests

Taku River records since 1987

1. 45.07 ft. on July 25, 2004

2. 44.19 ft. on July 22, 2007

3. 44.13 ft. on Aug. 17, 1989

4. 43.88 ft. on July 30, 1994

5. 43.77 ft. on July 26, 2000

6. 43.23 ft. on July 26, 1995

7. 42.89 ft. on July 28, 1993

8. 42.68 ft. on June 7, 2007

9. 42.46 ft. on Aug. 20, 1992

10. 42.34 ft. on June 30, 2005

Information provided by National Weather Service

As of Monday afternoon, the flow was down around 45,000 cfs, Hess said.

The National Weather Service released flood warnings on Friday, which were subsequently canceled after the river began to subside. A U.S. Coast Guard H-60 Jayhawk helicopter patrolled the area in case anyone needed to be rescued, Petty Officer Brandon Cervantes said.

"There was no significant damage (reported)," he said. "The water was pretty high, but it started subsiding (Sunday) afternoon."

Hess, who was up the Taku this weekend to monitor the release, said there didn't appear to be a tremendous amount of debris in the river. Logs and ice chunks are hazards associated with glacier dam releases.

Cabin owner Errol Champion said he has not heard any significant damage. Most cabin owners on the Taku River are accustomed to the annual cycle, he said.

"We understand how those floods occur and most of us have built our cabins up in the air to deal with it," he said.

Champion said the floods have been something people living up the Taku have dealt with for years.

"There's been higher floods back in the '60s," he said.

The 2004 flood is still is in the minds of many property owners, Champion said.

"Most of them are relieved that it is not as high as 2004," he said of Sunday's flow.

A lot of questions remain about how the glacier dam release occurs from Lake No Lake, Jacobs said.

"In time we're getting to know more and more about this, but there is still a lot of unknowns," he said.

Recent research suggests the lake must rise to a critical level to trigger the release, which then travels through ancient tubes in the ice or possibly lifts the glacier up and flows underneath it, Jacobs said.

"It seems like it is all subterranean, underneath the glacier," he said. "It doesn't flow over the top of the glacier."

There are a lot of different variables that make predicting glacier dam releases difficult, Hess said.

"It's so hard to predict how and how much comes out of that lake," he said.

The National Weather Service wants to collect more information about Sunday's flood from those in the area, Jacobs said.

"We're itching to get some hard facts," he said.

People aware of any damage or flooding that occurred due to the release are encouraged to call the National Weather Service in Juneau at 790-6824.

• Contact Eric Morrison at 523-2269 or eric.morrison@juneauempire.com.



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