Flood advisory in effect for areas along Matanuska River

UPDATE: Saturday, 7:30 p.m.

The National Weather Service has upgraded a flood watch to a flood advisory for areas along the Matanuska River after a day of heavy rain and rising water levels.

Water volume was 28,600 cubic feet per second at about 2 p.m. Saturday but was expected to reach 34,000 cfs by 10 p.m., according to the advisory.

About 30,000 cfs is enough to cause minor flooding along portions of the Glenn Highway east of Sutton between miles 64 and 66, the advisory states. Volumes of 35,000 cfs can trigger significant and widespread flooding along areas near the river — similar to what occurred in 2012, when the river reached a comparable height, the advisory says.

The flood advisory was issued at about 3:45 p.m. Saturday and is in effect through 6 p.m. Sunday.

Original story:

What you need to know:

• The National Weather Service has issued a flood watch through Monday for areas along the Matanuska River in Palmer and Butte, as well as for small rivers and streams northeast of Sutton. Residents near mountain slopes should watch for possible landslides.
• The watch is tied to heavy rain expected between Sutton and Mendeltna through Sunday morning, which could send a high volume of water down the Matanuska River.
• The watch follows flooding in late June along the Matanuska River in Butte, where the current broke through the riverbank in three places, inundating private property and structures along the Old Glenn Highway.

PALMER — The National Weather Service has issued a flood watch for areas along the Matanuska River in Palmer and Butte due to heavy rainfall expected northwest of Sutton over the weekend.

The watch also warns of potential flooding near small rivers and streams between Sutton and Eureka.

The watch was issued Friday and extends through Monday afternoon, according to the notice.

The potential flooding is tied to high water moving into small rivers and streams and down the Matanuska River, driven by one to two inches of rain expected between Sutton and Mendeltna through Sunday morning, the notice states.

Some locations along the Matanuska River could reach bankfull by early Sunday morning, the notice states.

Residents near mountain slopes should be prepared for possible slides, it states.

State transportation crews on Saturday cleared a small rockslide from the roadway triggered by rainfall at Mile 68 of the Glenn Highway between Sutton and Chickaloon, Department of Transportation officials said. The slide did not close the roadway, they said.

The heaviest rainfall is expected in the mountainous terrain along the Glenn Highway corridor between Sutton and Eureka, according to the notice.

That rain could push water volume in the river higher than levels seen in early July after the river’s powerful current broke through the bank near Butte, moved down a bike path along the Old Glenn Highway, and flooded about 10 private properties or structures.

A multiweek Alaska Department of Transportation emergency repair project used gravel and large rock reinforce three break points along the bank. An informal levee at Maud Road was also repaired.

State transportation officials said Saturday they are actively monitoring potential erosion areas along the river near both the Old Glenn Highway and the Glenn Highway.

This story was updated on Aug. 2 to include information from state transportation officials and details about a slide on the Glenn Highway.

-- Contact Amy Bushatz at contact@matsusentinel.com