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The floods of February 10-15, 1969., were the highest known on many streams in southern Idaho and northeastern Nevada. Some of the peak discharges have recurrence intervals greater than a hundred years.
The floods resulted from an unusual combination of conditions, each of which contributed to the sudden severe flooding. These conditions were an extended period of above-freezing temperatures and prolonged light rainfall, an extensive area of snow at low altitudes, and deeply frozen ground, The snow at higher altitudes did not contribute to the floods.
Runoff was greatest from watersheds at altitudes ranging from 4,500 to 6,500 feet. Flooding from small tributaries with large parts of their drainage within this range rank among the highest snowmelt floods ever recorded in Idaho and northeastern Nevada. The Snake River main stem had only minor flooding.
The flood damage was the greatest ever experienced in most of the flood area because of the large areas inundated and because the value and amount of improvements has increased steadily. The total damage has been estimated as more than $10 million.
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Floods of February 1962 in southern Idaho and northeastern Nevada