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Flood watch for Mendenhall Lake & River as glacial dam bursts, trails to close
Published: 07/05/2012 10:41:00
Updated: 07/05/2012 18:45:00

Southeast Spotlight Report: Mendenhall Flood 2012 Update
VIDEO: Southeast Spotlight Report: Mendenhall Flood 2012 Update (Image: Mikko Wilson / KATH-TV)


The Mendenhall River flooding at Mendenhall Loop Road bridge at 6:37am July 21st 2011
The Mendenhall River flooding at Mendenhall Loop Road bridge at 6:37am July 21st 2011 (Mikko Wilson / KATH-TV)

A river gauge shows the rapid rise in the Mendenhall River (7/5/12 10:00 AM)
A river gauge shows the rapid rise in the Mendenhall River (7/5/12 10:00 AM) (NWS/USGS)

A lake gauge shows the rapid rise in the Mendenhall Lake (7/5/12 10:15 AM)
A lake gauge shows the rapid rise in the Mendenhall Lake (7/5/12 10:15 AM) (NWS/USGS)

Related:
Mendenhall Lake and River flood following burst glacial ice dam, water begins to recedes during the afternoon

The National Weather Service in Juneau has issued a FLOOD WATCH for the Mendenhall Lake and River due to a jokulhlaup (glacial surge) caused by an ice dam in "Suicide Basin" on the Mendenhall Glacier failing. Water levels are expected to crest Friday morning.

The event is similar, though possibly slightly smaller, than a flood in July 2011 caused by the same phenomenon. The lake behind the glacial dam was observed by a Civil Air Patrol flight on June 23rd, and hydrologists at the Weather Service have been watching the river very closely since. They issued the flood watch Wednesday afternoon as water levels in the lake started to rise rapidly in a way consistent with a glacial dam release.

As of 11:15 AM Thursday, the Mendenhall Lake level was observed at 6.86ft, up from a normal level of around 5ft. The lake is expected to crest at about 9.5ft in the early hours of Friday. Flood stage for the lake is 9ft.

As of 10:00 AM Thursday, the Mendenhall River level at the Mendenhall Loop Road bridge was 9.4ft, up from a normal level of about 8ft. The river is expected to crest at about 12ft, well above the flood stage of 11.5ft.

In a press release at 11 AM Thursday, the US Forest Service warned people to stay away from the banks of the river as they may be unstable and give way. Time on bridges should be minimized as they are not a safe place to stop or stand to take pictures. "The U.S. Forest Service Juneau Ranger District is closing the West Glacier Trail on Thursday morning. The Nugget Falls Trail is expected to close early afternoon Thursday. The Mendenhall Lake Campground and road into the recreation area are currently open; however, a few vulnerable camp sites have been closed" states the press release. It goes on to warn: "People are encouraged to use caution while recreating in the area. Boaters on the lake should stay away from the face of the glacier and avoid using the river until further notice. Hikers along Mendenhall Lake should watch for waves from glacial calving."

This is a developing story and will be updated as conditions warrant.
We are also posting updates on twitter at @kathtv with the hashtag #Mendenhall.

Updated forecasts and warnings are available directly from the National Weather Service in Juneau at the link below.

http://pajk.arh.noaa.gov/

By: Mikko Wilson - mikko@kath.tv