Warnings first came last week about the Boise River’s planned rise. On Tuesday, it should reach roughly 7,000 cubic feet per second, right at flood stage as measured at the Glenwood Bridge in Boise.
On Monday, the Idaho Office of Emergency Management warned of a greater flooding risk in Weiser. The National Weather Service forecasts the Weiser River, as measured on the south edge of town, may reach nearly 14 feet deep on Friday morning — considered “major” flooding.
“Highway 95 expected to be covered with water,” the Idaho agency warned in a tweet.
Designated flood stage at that point is 9.5 feet. When Weiser saw its flooding troubles in February, the river reached 12 feet. The National Weather Service’s predictions can be monitored online here.
(Different rivers can carry different amounts of water, and their flood stages are tracked in different ways. But for comparison with the Boise, roughly 23,000 cfs will pass along the Weiser if it rises as high as forecast Friday.)
Along the Boise, the planned increase to flood stage is designed to help reduce the risk of increased flooding this spring from rapid snowmelt and rainfall, the The U.S. Army Corps of Engineers and U.S. Bureau of Reclamation say.
The Corps began releasing an additional 250 cfs per day from Lucky Peak Reservoir on Monday to reach flood stage on Tuesday, the agencies announced Friday. As of 3:45 p.m. Monday, the river was running at 6,850 cfs at the Glenwood Bridge.
Intentionally increased flows two weeks ago prompted some closures and flooding along the Greenbelt in Boise, and as the river level rises, more submerged trail sections are anticipated and riverbank erosion could happen. Minor flooding also is anticipated on sections of Eagle Island and in other low spots along the river, officials said.
Real-time Boise River flows at the Glenwood Bridge and other locations are available online.