The Mississippi River Flood of 1965

The spring Mississippi River flood of 1965 stands as the flood of record for nearly half of the riverís length (from about 100 miles north of Minneapolis, MN to Hannibal, MO). At the time, the crests of that April (Fig. 1) exceeded previous records by several feet at many river gage sites. To this day, those record crests still out distance the 2nd highest crest by a foot or more at many of those same sites. The flood caused $225 million in damage to public and private properties, with $173 million of that occurring along the main stem of the Mississippi River. Emergency actions and evacuations, based on National Weather Service forecasts, prevented approximately $300 million in additional damage.

Several factors contributed to this record flood:
  • An early freeze in the fall of 1964 which lowered the frost depth deeper than usual.
  • Significant snowfall in March across the region (300% above normal in east and east central Minnesota).
  • Below normal temperatures for the last half of March and start of April, preventing the gradual melting and runoff of the snowpack.
  • Heavy rainfalls in early to mid April, falling upon the snowpack and frozen grounds. With nowhere to go due to the frozen ground, the rain and melted snow quickly found their way into the Mississippi River and its tributaries. This runoff would create the record flood.
image of the record flood stages along the Mississippi river in 1965
Fig 1. Location, crest, and day of crest for the 1965 Mississippi River flood. All locations listed recorded their all-time record crest.


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