Rogue rising, to hit flood stage
TRAIL — An extremely rare spring tropical rainstorm falling on a thick snowpack caused federal hydrologists Monday to severely ramp up Lost Creek Lake releases into the Rogue River to ensure the reservoir doesn’t fill.
The U.S. Army Corps of Engineers ramped up Lost Creek dam releases from 5,800 cubic feet per second early Monday afternoon to 10,000 cfs by Monday night to slow down the rapid filling of the reservoir that’s forecast to top out at mere inches from full.
Those are the highest releases from Lost Creek Lake since the Jan. 1, 1997, flood that was the most recent significant flood on the Rogue, records show.
By the time inflows were expected to peak at 5 a.m. Wednesday, the reservoir would have risen almost 8.5 feet to an elevation of 1,871.2 feet above sea level — just shy of the full pool elevation of 1,872 feet, forecasts show.
“That’s why I’m being as aggressive as I am,” said Corps hydrologist Kevin Mcallister, who regulated the Rogue Basin Corps projects. “That doesn’t even get us a foot of buffer from full pool.”
If inflows increase higher than forecast, it could cause the Corps to up the reservoir releases even higher, something that would not have been necessary had the storm occurred during the regular winter flooding season and not near the end of the filling cycle.
“I’m just tying to mitigate risk for the project,” Mcallister said. “I’ll make flow increases as necessary.
“This late into the springtime I haven’t seen anything in the historical data that matches what we have right now,” Mcallister said.
The Lost Creek releases, coupled with other stream runoff, have pushed the Rogue levels right to flood stage at Dodge Bridge near Eagle Point at just shy of 25,000 cfs. However, flows would be much higher at Dodge Bridge because the release, for instance, at 2 p.m. Monday to the upper Rogue from Lost Creek were about 8,500 cfs less than inflow.
Rogue flows were setting record early April levels river-wide Monday, but it was forecast to remain under flood level at the old Gold Ray Dam site and Grants Pass, according to the Northwest River Forecast Center, an arm of the National Oceanic and Atmospheric Administration.
The Rogue was about a foot above flood stage in Agness at 2 p.m. Monday and forecast to peak Tuesday just shy of 3 feet above flood stage. However, with it peaking at a gauge height of 18 feet at Agness on Tuesday, that still is 50 feet shy of the Dec. 22, 1955, record of 68.03 feet, according to the forecast center.
Flows into Lost Creek are forecast to peak above 16,000 cfs about 5 a.m. Tuesday, then slowly rescind until they are forecast to drop below 10,000 cfs at 11 p.m. Wednesday.
This differs from typical storms when flows into Lost Creek spike up and drop quickly after reaching peak inflow, Mcallister said.
“It’s going to take us a long time to get those flows down,” he said.
Mcallister had been preparing for this event since last week by drafting the reservoir down below the normal filling curve.
“I’m really glad we did that,” Mcallister said. “I’m trying to find this balance.”
Reach Mail Tribune reporter Mark Freeman at 541-776-4470 or email@example.com. Follow him on Twitter at www.twitter.com/MTwriterFreeman.