REMEMBER:
DIKES ARE SAFE AT PRESENT
YOU WILL BE WARNED IF NECESSARY
YOU WILL HAVE TIME TO LEAVE
DON'T GET EXCITED. Bulletin to Vanport residents from the Housing Authority of Portland, Sunday morning, May 30, 1948

Below, Vanport houses were never meant to be permanent. Constructed on wooden foundations, they floated "like corks" during the flood. Courtesy of Bonneville Power Administration
      Vanport's post-war survival efforts came to an rapid halt when in 1948 warm May temperatures rapidly melted snow in the mountains that feed the Columbia. The river's waters rose, passing the 15-foot flood stage early in the month. By the 25th, the Columbia and Willamette Rivers reached nearly 23 feet. That day, patrols began checking Vanport's north and south dikes for boils or blisters. Later in the day, patrols checked the the west dike (railroad fill that burst) when Smith Lake's rising waters reached it.

The Columbia floodplain under water, May 1948. Courtesy of Bonneville Power Administration

As the surging waves first moved in, they quickly hit the many sloughs. One report described showers of spray 50 feet high upon impact with the slough water. Then, for 35 to 40 minutes a creeping inundation occurred as the sloughs absorbed much of the water. After they were filled and a sheet of water had spread over Vanport, the waves began to roll again; cars were sent careening, houses wrenched apart; the water reached the high part of the project near Denver Avenue, and all vehicular traffic was quickly flooded out. Now the water level rose rapidly. Between 5:00 P.M. and 6:45 P.M. the Willamette River flood gauge dropped three inches during the massive run-off into Vanport.