What if Lost Creek dam failed?
SHADY COVE — If some calamity ever caused a catastrophic failure at Lost Creek dam, residents of this little Rogue River town would have three hours to head to high ground before flows would rise nearly 100 feet, authorities say.
The results, as outlined by newly updated "inundation maps" prepared by the U.S. Army Corps of Engineers, are virtually the same whether an earthquake collapses this embankment dam during a sunny May afternoon or it fails in the midst of a super-storm in the upper Rogue Basin watershed, according to the Corps.
The chances of such failure at Lost Creek and Applegate dams are so remote that Corps officials can't put a number on their probabilities, but the federal agency calculates to create the maps outlining these worst-case scenarios.
"As improbable as the worst-case scenario is, the consequences would be severe," says Jim Buck, the Corps' Rogue Basin project manager. "Hopefully, those who live downstream of the dam will have thought about how to get to high ground."
If not, then the Corps will give them the opportunity.
Agency officials are planning small-group presentations during reservations-only meetings in Shady Cove Sept. 21 and again in Grants Pass Sept. 22 to share aspects of these maps and explain to Rogue Basin low-landers along the rivers what their risks are of dam-failure.
To reserve a spot at the Sept. 21 map viewing in Shady Cove, visit https://rogue-maps-shady-cove.eventbrite.com. To reserve a spot at the Sept. 22 map viewing in Grants Pass, visit https://rogue-maps-grants-pass.eventbrite.com.
The small-group meetings will run between 3 and 8:30 p.m. and include presentations by Corps officials on the depth and path of water under catastrophic failure scenarios along the Rogue and Applegate rivers below their respective dams.
Corps spokesman Scott Clemans says the maps include sensitive Homeland Security Agency data so they can't be sent electronically or shared randomly in public. In general, however, those living within a mile of the Rogue would be most interested.
"These maps are not designed for the general public," Clemans says. "They're designed for local area emergency managers to understand what the risk is."
But so far, the Corps has yet to provide Jackson County Emergency Manager Sara Rubrecht enough detail to prepare a plan to match any of these scenarios.
Rubrecht says she so far has small maps with inundation areas shaded — enough to see what neighborhoods would be under water but not down to property-by-property or what the levels of inundation would be.
Without it, Rubrecht says, she cannot put together a notification system to affected residents as Ashland has in case of catastrophic failure of its Hosler Dam on Ashland Creek because she doesn't know which residents to notify along the Rogue or Applegate rivers.
If she had the information and an actual failure occurred, "I could push a button and let everybody know," she says.
Also, she can't give people information about what roads to use as escape routes without knowing exactly what roads would be under water, Rubrecht says. Same goes with identifying facilities for shelters, she says.
"I need more information than a shady area on a very tiny map," Rubrecht says.
Rubrecht says she has applied to the federal government to get that data but has yet to see it.
"It's been an adventure trying to obtain that data," Rubrecht says. "We're just trying to follow the rules and get that information. We'll get through it."
The updated maps include the two dam-failure scenarios — a so-called "sunny day" failure with a full spring pool and normal river flows, and a worst-case scenario of failure during a massive storm when downstream water levels were already high.
Buck says draft maps for a sunny-day failure calculate that Shady Cove residents would see a rise in the water in two hours and that level would peak at 92 feet above normal flows an hour later.
During the worst-case flood scenario, it would take about an hour for flows to show up at Shady Cove and they would peak at 97 feet above normal river level two hours later, Buck says.
Those levels are computed for a cross-section of the Rogue near Shady Cove's downstream city limits, Buck says.