Portland, OR — The U.S. Army Corps of Engineers is monitoring Columbia Basin flood events encompassing the Seattle, Portland and Walla Walla districts areas of responsibility on the Columbia River. Columbia Basin Water Management Division initiated emergency flood risk management protocols this week due to a Flood Warning issued by the National Weather Service for the lower Columbia River.
USACE Dams are routinely inspected and are working as designed, with storage projects high in the basin storing flood water to reduce flows downstream during this current weather event. Although areas within the basin have lost some snowpack, there remains a lot of mountain snow within the Columbia River Basin. This current precipitation/warming event is a short-term event that has caused rivers to swell and storage reservoirs to fill slightly. For the past few months Columbia River Basin storage projects have been releasing water from storage to meet flood risk management requirements for March and April. Once this event passes, continuing to move large volumes of water out of storage dams to prepare for future weather systems and to ensure adequate reservoir space is available for flood risk management during the spring snowmelt period will be necessary. These releases will likely place several communities (Vancouver, WA / Boise, ID) at or near flood stage for several weeks. Heavy rain events between now and mid-April may make this challenging.
The dry weather on March 16 allowed flows in several of the smaller tributaries to recede. Locations on the main stem Columbia and Snake rivers, and locations experiencing significant snowmelt, are continuing to see increasing river stages. The weather system moving through the Pacific Northwest Friday and Saturday is expected to increase river levels in Idaho and the eastern portions of Oregon and Washington, and to a lesser extent in western basins.
The Columbia River at Vancouver is currently at its flood stage of 16 feet and is expected to rise to 17 feet. When levels are above 16 feet can some islands and low areas will experience flooding with minor impacts to parks and trails along the river. When levels are above 17 feet some lowland access roads, parking areas, and trails on Sauvie Island, around Vancouver Lake, and near downtown Vancouver will be flooded. Additionally, access to some house-boat communities will be impaired. Recreation and camping areas at Cottonwood Beach near Washougal and on Government Island will be impacted. When levels are above 18 feet, unleveed lowland, pasture, and farmland will begin to flood. The main impacted areas have historically been from Sauvie Island downstream to Woodland, WA. There will also be some inundation of parks and trails along the Columbia in and near Vancouver and Portland. To track and understand direct impacts please visit the National Weather Service’s Advanced Hydrologic Prediction Service.
Flows are forecast to remain high through the month as upstream storage projects increase releases to create reservoir space to store spring snowmelt. The Willamette and Columbia rivers join together near Portland and Vancouver. As Willamette River flows recede, flows through dams on the Columbia River can increase, likely holding the gage at Vancouver within 1-foot of flood stage.
Public safety is a priority and the public is urged to follow local emergency management officials for guidance if necessary.
For maps of hydrology on the Columbia River visit the Northwest River Forecast Center:
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