Flood of 1948

On this date 77 years ago, Fairbanks was experiencing the worst flood in the short history of the city up to that time.  It would go on to be exceeded by the August 1967 flood, but May 1948 remains the second worst flood, and the worst springtime flooding event.

The event was not a breakup flood, although breakup was very late that year, occurring on May 10 on the Chena River in Fairbanks, and May 13 on the Tanana River at Nenana.  Rather, the flooding arose about a week later from tremendous snowmelt runoff in the hills.

The stage was set a month or more earlier, as very heavy precipitation occurred from late March into April.  Valley-level temperatures were marginal for snow during the sustained precipitation of April 7-14, but it would have been cold enough in the hills for snow to continue accumulating.  Here's the data from the Fairbanks climate record:

Notice the cold that developed in mid-April, preserving the snowpack at a time of year when it would normally be starting to diminish, depending on elevation.  Overnight temperatures were still falling below 20°F in early May - hence the late breakup - but then spring finally emerged on May 9, and there was no looking back.

It's difficult to say how much snow may have actually been on the hills above Fairbanks by the time the big thaw arrived.  The preceding winter was quite warm until February, and not particularly wet, so it seems unlikely there was a big snowpack going into March; but the 3" of new precipitation in Fairbanks in late March and April would have added at least 4-5" of liquid to the elevated snowpack, perhaps much more.  There have been other years since with snowpacks that were greater, but back in 1948 the combination of sudden melt and a lack of modern flood defenses produced a very unfortunate outcome.

Here's a silent clip from the Alaska Film Archives documenting the event.

https://www.youtube.com/watch?v=S-u7m0uL7Kc