CANYON CITY — A specialized U.S. Forest Service team studying the impacts of the Canyon Creek Complex fire has projected that a major storm event could result in catastrophic flooding along Canyon Creek.
The projections show a possible scenario that is difficult to imagine but could have disastrous effects on Canyon City and John Day, said county engineer Doug Ferguson.
The flooding danger will go down as vegetation returns to areas heavily damaged by the fire, “but we’re facing a real dangerous situation right now,” he said.
The projections by the Forest Service’s Burned Area Emergency Response team of experts show that a 10-year storm would cause Canyon Creek flows to peak at levels scarcely imaginable before the 110,000-acre CCC fire.
A 10-year storm would now cause Canyon Creek flows to peak at 1,997 cubic feet per second. Before the fire, such a storm would have caused flows to peak at 661 cfs, BAER team members estimated.
During the 2011 flood that damaged part of the high school, Canyon Creek flows peaked at 856 cfs. That rainstorm was considered a 40-year storm.
In fact, based on estimates by the Federal Emergency Management Agency, a 100-year storm would result in Canyon Creek flows of 1,500 cfs.
Because of the loss of vegetation caused by fire, “a 10-year storm would be devastating, according to (BAER) figures,” Ferguson said.
The BAER team included hydrologists and engineers and Ferguson said the methodology they used to arrive at those numbers is sound.
“The reasonableness of their (calculations) is evident,” he said.
Ferguson is now working with BAER team members, Army Corps of Engineers officials and other agencies to produce a map that shows exactly how the creek would react after a 10-year storm and at what spots the damage would likely occur.
He expects to have that done in about two weeks to a month.
Ferguson has been tasked by Grant County Court with helping coordinate all the various restoration efforts by local, state and federal agencies aimed at mitigating the danger of a catastrophic flood.
Grant County Court Commissioner Boyd Britton said the county is trying to be very proactive about preparing for such a flood and he would rather play the role of Chicken Little and be wrong than not prepare properly and have a disaster.
“I’d like to be real proactive about this as much as possible,” he said.
Ferguson said a lot of effort is gong into addressing the issue — “A lot of powerful people are working on this. It hasn’t gelled yet but I feel like it’s going in the right direction.”
But, he added, there’s little that can be done right now to prevent a catastrophic flood from occurring if a major storm hit the area today.
Such a flood would bring a lot of debris with it and if that debris didn’t get cleared out rapidly, it could quickly take down bridges near Canyon City, he said. To prepare for that scenario, the county plans to move excavators into strategic areas so debris can be cleared quickly to prevent bridges from plugging up.
An alarm system to alert people to imminent flooding, which the BAER team recommended, is another thing the local community can do quickly to prepare for flooding, Ferguson said.
Canyon City Mayor Steve Fischer said the BAER estimates are a worst-case scenario “but if it even comes close to the worst-case scenario, the potential for property loss and damage could exceed what the fire did.”
Fischer has discussed the issue with Ferguson and city council members and has been told the county court is waiting for permission to remove 50,000 yards of material out of the creek bottom to mitigate the flooding potential.
Canyon City will assist the court on that effort, he said, including contacting all property owners along the creek and getting their permission for people conducting the creek debris removal to enter their property.
John Day City Manager Peggy Gray said the possibility of a disastrous flood is a major concern and the city is focusing on informing the public about the danger and urging them to get flood insurance.
The city included information in this month’s utility bill directing residents where to find more information about flood insurance.
City officials will also walk up and down Canyon Creek and identify hazards, Gray said.
“Anything we think could be a hazard, we’ll try to eliminate that hazard prior to spring and runoff,” she said. “We want to be prepared for what could come down the creek and the public needs to be aware of what the risks are.”
According to a BAER team report, it will take about five years for vegetation to recover in watersheds affected by the fire.
“Flood potential will decrease as vegetation re-establishes, providing ground cover, increasing surface roughness and stabilizing and improving the infiltration capacity of the soils,” the report states.