The Christmas Flood of 1964

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The Christmas flood of 1964 encompassed about 200,000 square miles, or roughly the size of France, resulted in 47 deaths, left thousands homeless and caused more than $540 million ($3.9 billion today) worth of damage. Areas in Oregon, Idaho, California, Washington and Nevada experienced record-breaking floods caused by three storms between Dec. 19 and Jan. 31. Agencies from federal, state and local governments will commemorate the 50th anniversary of the Pacific Northwest 1964 Christmas flood starting Dec. 10.

Flood Awareness

During this holiday season, the 1964 Christmas flood reminds us that flooding is a national problem and can happen anytime, anywhere. According to the National Weather Service, over the past 30 years, nationwide annual flood damages averaged $8.2 billion with 89 fatalities per year.

The Christmas flood of 1964 was driven by a series of storms, known as atmospheric rivers or “pineapple expresses,” that battered the region producing as much as 15 inches of rain in 24 hours at some locations. The combination of heavy rain, melting snow, and frozen ground caused extreme runoff, erosion and flooding.

“It was a classic rain-on-snow event,” said Marc Stewart a hydrologist for the U.S. Geological Survey.  “In addition to the rain, there were already several inches of water from the melting snow, so it was a big runoff event across a wide area.”

The flood caused record-breaking peak streamflows, transported large amounts of sediment, and inflicted extensive flood damage.  However, in many areas storage in reservoirs and operation of flood-control facilities prevented far greater damage.

Flood Mitigation

Today, the USGS helps mitigate flood hazards by developing real-time flood inundation mapping capabilities and providing critical information about the nation’s rivers and streams.

“USGS streamgages are vital for flood risk management,” said Mary Karen Scullion a Willamette Valley reservoir regulator with the Army Corps of Engineers in Portland. “Changes at a gage upstream of our dam tells us how much more water is flowing into the reservoir. We cannot allow a dam to overfill.”

Streamflow data are vitally important for USGS partner agencies to forecast flood magnitude and timing, operate flood control systems, and manage emergency response.

“Water managers from state and federal agencies manage river flows near major population areas like Salem or Portland as a system of control points and each control point has a specific target,” said Scullion. “If a control point spikes, decisions are made that specifically address the needs of a population area. That’s when we need to decide how best to protect the region.”

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Flood Response and Evaluation

The USGS also coordinates collection and dissemination of geospatial imagery and map products used for flood response and evaluation. The USGS Flood Inundation Mapping Program focuses its efforts at state and local levels to help communities understand flood risks and make cost-effective mitigation decisions. The USGS partners with local communities to assist in the development and validation of flood inundation map libraries. Communities use these maps to help protect lives and property.

Learn More

• USGS 1964 Flood Commemoration
• Flood Ready Campaign
• Hydrologic Information Center – Flood Loss Data
• Heavy Rain in Thirsty California
• U.S. Geological Survey Flood Inundation Mapping Science
• The StreamStats Program