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Picture of flooding on the Wind River, Wyoming.

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1964 Northwestern Montana Floods - 50-Year Anniversary

What happened?

    Heavy rain began falling on snow and saturated soils throughout northwestern Montana on the morning of June 7, 1964. Twenty-four hours of rain added water to streams that were already running high from seasonal snowmelt. The storm resulted in one of the most devastating floods in Montana's recent history on both sides of the Continental Divide.

    The Flathead River west of the Divide and the Dearborn, Sun, Teton, and Marias Rivers east of the Divide carried record-breaking flows causing wide-spread flooding. Local areas near rivers in Glacier National Park and Waterton Lakes National Park that flow north to Hudson Bay also experienced flooding.

    Gibson Dam, on the Sun River remained intact despite overtopping. However, on the Blackfeet Reservation, Swift Dam on Birch Creek and a dam on Two Medicine River both were breached, quickly releasing large amounts of water. People in the narrow valleys downstream from these structures had very little time to escape the walls of flood water.

Picture of 1964 flooding in Montana.
^ Sun River overtopped Gibson Dam when flood waters poured into the reservoir upstream. The dam was designed to overtop, and remained standing during the duration of the high flows.

Map showing area of 1964 flooding in Montana.
^ General area of flooding during June 1964 and locations of current USGS streamgages within the area.

How bad was it?

    Twenty-eight people perished as a result of the flood waters in Birch and Two Medicine Creeks; ultimately 30 people lost their lives in the floods. Nearly 350 were injured, and about 8,700 received shelter and food from the Red Cross. Total damage in Montana was estimated at $55 million, and damages totaled more than $1 million in Canada (1964 dollars).

Picture of 1964 flooding in Montana.
^ Badger Creek washes out U.S. Highway 89 Bridge.

Will these rivers flood again?

    The map to the right shows that flood waters inundated areas far beyond the Flathead River channel near Kalispell. Similar broad swaths of flood waters also inundated parts of the Blackfeet Indian Reservation, Great Falls, Choteau, and St. Mary. The 1964 floods on the Flathead, Sun, Teton, and Marias Rivers are the largest in recorded history.

    Floods bigger than the "100-year" event have occurred, and likely will occur again. In an effort to better understand how frequently large floods occur, USGS hydrologists are studying recorded streamflow data from streamgages in and near the flooded areas as well as searching for clues about ancient floods in tree rings, tree scars, boulders, and sediments along river channels. Contact your local floodplain manager or call the Montana Department of Natural Resources National Floodplain Insurance Program Coordinator at (406) 444-6654 for more information to learn more about what you can do to minimize damage and loss of life in case of a flood.

Who can I contact for more information?

  • For more information, contact Katherine Chase at (406)457-5957 or kchase@usgs.gov

Map of 1964 flooding in Montana.
^ Areal extent of floodwaters from the Flathead River during the 1964 flood. (Excerpt from Boner and Stermitz, 1964)


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