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Picture of flooding on the Wind River, Wyoming.

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Floods of May 1978 in Southeastern Montana and Northeastern Wyoming

    Intense rain and some snow fell on previously saturated ground in southeastern Montana and northeastern Wyoming during May 16-19, 1978. The 7.60 inches that fell within a 72-hour period, measured at Lame Deer, Montana, set a record for the month of May in that region.

    Widespread flooding occurred in the drainages of the Yellowstone River and its tributaries as well as the Belle Fourche, Cheyenne, and North Platte Rivers. The previous maximum flood of record was exceeded at 48 gaged sites, and the 1-percent-chance flood was equaled or exceeded at 24 sites. Flood damage was extensive, exceeding $33 million. Nineteen counties in the two States were declared major disaster areas.

    Mean daily suspended-sediment discharges exceeded previously recorded maximum mean daily values at four sites on the Powder River. The maximum daily suspended-sediment discharge of 2,810,000 tons occurred on May 20 at the Powder River site near Arvada, Wyoming.


    Parrett, Charles, Carlson, D. D., Craig, G. S., and Chin, E. H., 1984, Floods of May 1978 in southeastern Montana and northeastern Wyoming: U.S. Geological Survey Professional Paper 1244, 74 p. | Report | Data |

Picture of 1978 flooding in Montana and Wyoming.
^ Flooding of Belle Fourche River at Interstate 90, near Moorcroft, Wyoming, May 19, 1978.

Picture of 1978 flooding in Montana and Wyoming.
^ Following flooding of Powder River (right center) at confluence with Yellowstone River, Montana, May 25, 1978. Peak flow occurred 2 days earlier.

Picture of 1978 flooding in Montana and Wyoming.
^ Following flooding of South Fork Powder River at Interstate 25, near Kaycee, Wyoming, May 25, 1978. Peak flow occurred 7 days earlier.

Picture of 1978 flooding in Montana and Wyoming.
^ Flooding of Lance Creek near Bright, Wyoming, May 19, 1978. The force of debris and water would have destroyed the bridge had the water not breached the road (fig. 26, Parrett and others, 1984).

Picture of 1978 flooding in Montana and Wyoming.
^ Headcutting from flooding, Powder River south of Powderville, Montana, May 25, 1978. Sedimentation was unusually large as a result of the flooding (p. 28, Parrett and others, 1984).

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