Flood advisory issued as emergency repairs begin along Matanuska River in Butte

What you need to know:

• State crews began emergency repairs Sunday to halt flooding from the Matanuska River near the Old Glenn Highway in Butte, even as the National Weather Service issued a flood advisory for the area.
• The river broke through a revetment and informal levee early Saturday, flooding a bike path and nearby structures and coming within feet of the roadway. The repairs are intended to stop the flow of water and prevent further damage.
• Waters are expected to recede over the week as temperatures cool. The riverbank repairs are not considered a permanent solution. Once state officials complete the current work along the bank, the borough will begin repairing the damaged section of Maud Road.

BUTTE – A section of the Old Glenn Highway in Butte was under a flood advisory Sunday as state contractors began repairs on a stretch of riverbank where the Matanuska River broke through the revetment early Saturday, flooding the bike path and nearby properties.

The advisory affects the Maud Road area between miles 13 and 15 of the Old Glenn Highway, officials said. The flooding is impacting about 10 private properties or structures and came within feet of the roadway Saturday, borough officials said. No evacuations have been ordered, they said.

While floodwaters that covered large sections of the bike path earlier in the weekend had receded by late Saturday into Sunday morning, the volume of water flowing down the Matanuska River was expected to crest at about 24,400 cubic feet per second Sunday afternoon, then drop off early in the week under cooling temperatures, according to the National Weather Service in Anchorage.

“Since this is largely driven by new erosion along the riverbank, persons in this area should continue to monitor the situation,” the advisory states.

Several buildings and private properties along the highway just south of Maud Road sat underwater around noon Sunday, with sandbags blocking the flow to some homes and businesses. A pair of Matanuska Electric Association trucks was holding poles in place against the flow of water down a right-of-way that runs alongside the roadway and bike path.

State transportation officials said they planned to install stabilizing material and large rocks known as riprap along about 100 feet of riverbank just above Maud Road early this week to halt water flowing toward the roadway and private property.

To complete the fix, crews must clear a roughly 300-yard path from the bike path and highway to the river, lay a gravel road to support heavy machinery, and remove a series of large trees from along the bank, officials said. They said they hoped to have the road under construction by midday Monday and begin repairs early this week.

The flooding began early Saturday as the river’s powerful current, swollen by runoff from the previous week’s warm temperatures, broke through a decades-old revetment installed along the river and a gravel section of Maud Road that has functioned as an informal levee against regular overflow, borough officials said. The informal levee was last breached about 10 years ago, they said.

Once the state repairs the riverbank and the water fully recedes, the borough will reconstruct the damaged section of Maud Road, said Casey Cook, a Mat-Su Borough emergency manager who reviewed the flooding with borough and state officials Sunday.

While the flooding is impacting private properties and some borough land, the state is responsible for stabilizing the riverbank because the erosion threatens the highway and the electric grid, Cook said.

The revetment fix should provide a temporary solution to hold back the river through the season, including over its peak flow in September, said Jonathan Tague, a state project engineer overseeing the work. A more permanent fix will need significant funding and coordination with the Army Corps of Engineers, he said.

“This is just responding to the emergency,” Tague said.

-- Contact Amy Bushatz at contact@matsusentinel.com