Disastrous storm pushed Oregon dam to its limits

PORTLAND, Ore. (KOIN) — The Galesville Reservoir near Azalea, Ore. was operating near capacity this week, after 4 to 5 inches of rain fell on southwest Oregon between March 14 and 16.

The heavy rain flooded towns, washed out roads and turned hillsides into streams of mud. Douglas County spokesperson Tamara Howell told KOIN 6 News that the storm pushed the Galesville dam to its limits on March 17 and 18, filling the 42,225-acre-foot reservoir to the brim.

“Until [Tuesday], we were all holding our breath with the possible spillover at Galesville Dam,” Howell said Wednesday.

The dam prevented multiple communities from more-disastrous flooding, according to Douglas County.

“While most people think of the Galesville Dam as a conduit for irrigation in southern Douglas County, this time it acted as a major flood-control device, saving the communities of Glendale, Riddle, Myrtle Creek and Winston from even greater flooding and additional carnage,” Howell said.

According to U.S. Geological Survey data, the reservoir’s outlet, Cow Creek, saw its highest streamflow since 2006 on Monday. Oregon State Climatologist Larry O’Neill said that the creek was experiencing a streamflow of 1,340 cubic feet per second while the dam was near capacity.

“My understanding is that the dam itself was not in immediate danger of an uncontrolled overflow, but it was operating near capacity,” O’Neill said.

The creek reached the third-highest water levels since the dam was built in 1986. The largest streamflow ever recorded on Cow Creek happened on Jan. 15, 1974 (10,600 cubic feet per second). The catastrophic flood of 1964 brought the creek to 8,430 cubic feet per second.

The end-of-winter flooding prompted Gov. Tina Kotek to declare a state of emergency for the region. Local and state officials are still assessing the damages caused by the storm. However, Coos County Commissioner Drew Farmer told KOIN that officials are worried that the retreating waters may bring more damage.

“With some roads still being flooded we have concerns that, once the water recedes, we will see a suction effect that will pull additional material out from under our roads resulting in additional road failures,” Farmer said. “I made it around most of our cities and some outlying communities [March 17] and the problem is substantial.”