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Boise River on rise again; most of Greenbelt closed

Prepare for flooding, Ada County officials say

The unpredictability of weather and flood flows means Ada County residents in low-lying areas along the Boise River should be prepared, Ada County officials said at a media briefing Thursday.
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The unpredictability of weather and flood flows means Ada County residents in low-lying areas along the Boise River should be prepared, Ada County officials said at a media briefing Thursday.

Boise and Garden City were closing most of their segments of the Greenbelt at 6 p.m. Thursday, leaving just 11 miles open, mostly on one side of the Boise River.

What’s not closed? Here’s a map.

You can still stroll along the north edge of Boise State University, and near Boise’s Esther Simplot and Whitewater parks. The longest stretch still open runs the river’s north side from roughly Warm Springs Golf Course to Lucky Peak Dam, with a fair amount of the southern path open in that area as well. (One version of the city’s map distributed Thursday afternoon suggested more of that section was closed than is actually the case.)

The closure is both for the public’s safety and that of first responders who would be called to any water rescues, according to a notice from the city of Boise.

“No one, no matter how strong of a swimmer, would be able to last long in the current and temperatures we’re seeing in the river right now,” Boise Fire Chief Dennis Doan said in the notice.

River managers say they’ll increase flows — as measured at the Glenwood Bridge — to 8,500 cubic feet per second by Wednesday. That would put it back on par with flows March 30, when Ada County emergency management officials gave a media briefing about ongoing high flows and flooding concerns.

The news is just the latest in ongoing attempts to clear space in reservoirs across Southern Idaho and prevent worse flooding later this spring, when Idaho’s ample mountain snowpacks melt.

Managers still don’t believe there is enough space in reservoirs upriver of Boise to hold all of that snowmelt. The Boise River’s reservoir system was about 67 percent full as of Thursday.

The river Thursday was at around 8,100 cfs at the Glenwood Bridge. (For the latest conditions, follow this link.)

Flood stage for the Boise River is 7,000 cfs. We passed that in early March.

Next week’s extra water depends on the U.S. Army Corps of Engineers finishing an emergency levy at a gravel pit operated by Sunroc Construction and Materials, near Eagle Island. County and federal officials worry the riverbank could collapse there, redirecting the river into the pit — and then who knows where else.

Ada County authorities believe they’ll have 12 to 24 hours to warn locals of significant flooding around Sunroc, said Angie Gilman, county engineer.

Flooding has swamped large parts of the Greenbelt — Eagle closed the entire stretch within its city limits on Wednesday.

If the river stays on its current course, the county believes any other minor flooding will be manageable. But no one is sure what rain or sudden warmth might do, and how much more river levels will need to rise this spring.

Flooding was seen along the Boise Greenbelt off of Veterans Memorial Park on Friday. The Boise River was spilling over its banks and onto sidewalks and bridges with high river flows.

Extensive erosion from the Boise River at flood stage has forced officials to remove the south bridge leading to Plantation Island along the Boise Greenbelt in Garden City. On Monday, April 3, 2017 Inland Crane Co. was hired to hoist the bridge of

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