PORTLAND, Ore. – In early February 1996, a jet stream steered a warm pineapple express into a snow-covered Pacific Northwest.
This weather system, named “pineapple express” for its origins near Hawaii, was a river in the sky that drenched Oregon and Washington with 15 inches of rain over four days. The rain then combined with another foot of water from melting snow. From February 5-8, the rain “transformed streams into raging torrents and caused rivers to surge over their banks.”
Dairy cows drowned in their fields. Mudslides smothered roads and isolated towns. Fields of winter crops transformed into lakes.
And for the Portland District, U.S. Army Corps of Engineers (USACE), as the rain poured into rivers they manage, the flood waters became a crucible for their water management function.
Below are excerpts from the book, “Currents of Change,” a history of the Portland District from 1980-2000.
The Corps took a number of immediate steps to lessen the flood’s impact. Before the rain intensified in early February, the Corps had been releasing water from its hydro projects to make room for spring runoff. Once the heavy rains began, it immediately started cutting back flows and storing water in its storage projects. Engineers and technicians at the North Pacific Division Reservoir Control Center (RCC) in Portland worked around the clock to manipulate more than 60 dams in the Columbia River system to minimize flooding. Managing river flows during the flood was a delicate balancing act, according to Cindy Henriksen, Chief of the RCC.
“There is a complex system of dams on Northwest rivers and streams,” she explained. “But not all of these dams are designed for flood control. Only one darn on the lower Columbia the John Day, has significant storage capacity.”
Despite the challenges in regulating water flow, Corps dams were successful in holding back the flow of water and reducing flooding. Perhaps their most visible success was in downtown Portland, which, because of its location at the confluence of the Columbia and the Willamette, was especially vulnerable. A number of uncontrolled tributaries entered the Willamette upstream of the city, and many experts predicted that the crest would top Portland ‘s floodwall, which protected the downtown area. In response to this threat, Portland’s mayor Vera Katz requested technical assistance from the Corps and asked for volunteers to help city crews reinforce the wall. In a matter of hours, the riverfront teemed with people filling sandbags, building a higher plywood wall, and reinforcing the plywood with concrete roads.
… The Corps contributed to the flood relief efforts in other ways as well. At The Dalles-John Day project, for example, the agency distributed more than 100,000 sandbags to outlying communities in four counties. At Mill Creek, Corps’ personnel worked to keep the rising waters at bay. When debris began backing up the creek on February 7, crews worked until midnight for many consecutive nights to clear the material.
In the flood’s aftermath, a dialogue began among government agencies, environmentalists, and citizens about the interplay between human development and the power of nature. The event underscored that while dams were a critical defense, a more holistic approach to flood risk management was necessary.
As USACE looks back on the 30 years since the flood, the lessons of 1996 continue to inform the mission. Its experts are committed to protecting communities, but with a broader understanding of environmental stewardship after the event shattered long-held certainties about flood management.
USACE will join the Oregon Chapter of the American Meteorological Society’s at 6 p.m. Feb. 23, for a commemorative event, “30th Anniversary of the February ’96 Floods” at the Oregon Museum of Science and Industry. Experts and engineers from USACE will be available to answer questions. The event is free and open to the public. Additional details are available on the Oregon AMS website at OregonAMS.com.