Willamette Valley Flood of 1996

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The Willamette Valley Flood of 1996 was part of a larger series of floods in the Pacific Northwest of the United States which took place between late January and mid-February, 1996. It was Oregon's largest flood event in terms of fatalities and monetary damage during the 1990s. The floods spread well beyond Oregon's Willamette Valley, extending west to the Oregon Coast and east toward the Cascade Mountains. Significant flood damage also affected the American states of Washington, Idaho (particularly the north of the state) and California. The floods were directly responsible for 8 deaths in Oregon, as well as over US$500 million in property damage throughout the Pacific Northwest. 30,000 residents were displaced from their homes. ^[1]

Flooding in Oregon during the Willamette Valley Flood of 1996.

An unusual confluence of weather events made the floods particularly severe. The winter season preceding the floods had produced abnormally high rainfall and relatively low snowfall. The heavy rains saturated the ground and raised river levels throughout January 1996. In late January, a heavy snowstorm padded snowpacks throughout the region. This was followed by a deep freeze that lasted for 6 to 10 days. The new layer of snow was quickly melted by a warm subtropical jetstream which arrived on February 5. The jetstream brought along further rains. The combination of the additional rain, the saturated ground, and the melting snowpacks engorged dozens of streams and tributaries, which in turn flooded into the region's major rivers. ^[2]

The Willamette River, which flows through downtown Portland, crested at 28.6 feet (8.7 meters), some 10.6ft. (3.2m) above flood stage. ^[2] The river came within inches of overtopping its seawall and flooding into Portland's downtown Tom McCall Waterfront Park. A major sandbagging effort involving civilians as well as the Oregon National Guard was launched throughout downtown Portland, and was maintained until the floodwaters began to recede on February 9. At least five rivers in Oregon crested at all-time highs during the floods. ^[2] The downtown areas of Oregon City and Tillamook suffered particularly high damage from the floods, and both were submerged for several days.