The Umatilla National Wildlife Refuge stretches along a section of the Columbia River that was completely submerged during the Missoula Floods, buried beneath Glacial Lake Condon -- a temporary lake that formed when floodwaters backed up...
The Umatilla National Wildlife Refuge stretches along a section of the Columbia River that was completely submerged during the Missoula Floods, buried beneath Glacial Lake Condon -- a temporary lake that formed when floodwaters backed up behind constrictions in the Columbia Gorge. This refuge, spanning both Oregon and Washington banks, preserves wetlands, riparian habitat, and desert shrub-steppe that have grown in the flood-deposited sediments. The flat terrain is characteristic of lake-bottom deposits: fine silts and clays that settled when the turbulent floodwaters finally stilled in the temporary lake. During peak floods, water levels here may have exceeded 1,000 feet above modern sea level, completely inundating the landscape. The refuge is now a critical stopover on the Pacific Flyway for migrating waterfowl, and the flood-deposited wetlands support diverse bird populations including sandhill cranes, tundra swans, and bald eagles. The contrast between the arid sagebrush uplands and the lush river bottomlands reflects the dual legacy of flood sediments and irrigation. This is where the destructive power of the floods created the ecological richness visible today.
Open daily, sunrise to sunset. No visitor center is staffed; the experience is self-guided. The McCormack Unit (Oregon side, 10 miles south of I-84 via Paterson Ferry Road) has an auto-tour route, a wildlife observation tower, photo blind, and short nature trail; gates open at dawn and close at dusk. Several units have seasonal hunting closures from October through January.
The refuge straddles the Columbia River along the lower Umatilla Basin, well within the inundation footprint of the Missoula floods. Floodwaters backed up behind the Wallula Gap constriction created Lake Condon, a temporary slackwater lake that filled the lower Umatilla, John Day, and Willow Creek valleys to elevations near 1,100 ft (340 m) during the largest events at 18.2 ± 1.5 ka. As Lake Condon waters stood and decanted between flood pulses, fine silt and sand settled out as slackwater rhythmites, which underlie the present floodplain soils and the wetlands the refuge was created to mitigate (the refuge itself was established in 1969 to offset habitat lost behind John Day Dam). Bedrock here is Miocene Columbia River Basalt; the flood-deposited silts above it produced the rich agricultural ground surrounding the refuge.
USGS released a detailed geomorphic map of the Umatilla River corridor (Scientific Investigations Map 3527) covering this stretch. No Umatilla-NWR-specific dating updates since the Balbas et al. (2017) 18.2 ka anchor.
The IAFI Lower Columbia Chapter covers this stretch and has published the Lower Columbia floods brochure that references Lake Condon inundation; the refuge itself does not host an IAFI panel or named partnership.
Best visited October through February for peak waterfowl numbers (winter is the prime season). The McCormack Unit auto-tour is the most accessible flood-geology vantage; bring binoculars.
Flood-extent overlay shows the maximum reach of the Missoula Floods.
The site in its place along the flood path, with the maximum flood extent drawn over the modern map.
View on the interactive map Searchable sites · 360° trails · flood reconstruction