The U.S. Army Corps of Engineers is building a levee at Sunroc Construction and Materials Thursday at the head of Eagle Island to prevent a capture of its gravel pit. That could change the route of the river and threaten homes and even Boise’s wastewater treatment plant.
I drove the river Monday from Caldwell to Boise, looking at the effects of the flows at 8,100 cubic-feet-pert-second (measured at the Glenwood Bridge). Another 2 million acre-feet of water sits as snowpack in the watershed, and just 320,000 acre-feet of space remains in the three-dam reservoir system. It’s certain the river is going to go up again, even though the Corps said Monday that it has no immediate plans to raise the flow.
The key word is immediate.
On Eagle Island, the river is running up to the edge of Artesian Road and is almost up to the bridge on Linder Road. Downstream in Caldwell, sections of the river expands into a lake that on Monday covered groves of cottonwoods and ran up to the edge of low-lying neighborhoods.
The flooding in Boise is less immediate. Its challenge is managing water in the city’s designated floodways. The tendency is, when water threatens people’s stuff, for the people who own the stuff to want to sandbag in those floodways. And they do that even if the floodways, by agreement when their subdivision was built, were supposed to remain open. The people who made those agreements are often long gone.
I’m working on a larger article for later this week that examines our flood risks, not just on the Boise River but other places around the state. Idaho officials are watching the Lost River and Mackay Dam, where seven times the capacity of the dam’s reservoir sits as snow in the Pioneer and Lost River and Boulder-White Clouds mountains. The Goose Creek watershed in southeast Idaho also is covered in record snow, and the Oakley Reservoir can release water at a rate of just 170 cubic-feet-per-second. Its spillway is uncertain.
So once again I remind readers to buy flood insurance, since it takes 30 days for a new policy to go into effect. That means if you buy today you won’t be covered until May 5 — the same day in 2012 when officials had to raise the river briefly to where it is today to prevent worse flooding later. Right now you are betting your home won’t be flooded in the next 30 days.
Download Code Red Mobile Alert and stay up on the latest official flood information from Ada County at https://adacounty.id.gov/accem/Flood-Information