Flooding and High-Flow Conditions in Wyoming and Montana
Greybull River near Basin, Wyoming
June 1963
N F Flathead River at Blankenship Bridge near Columbia Falls, MT
1964
Swiftcurrent Creek at Many Glacier, MT
Nov. 7, 2006 @ 1400 hrs
Wind River near Crowheart, WY
June 15, 2017 @ 13,300 ft3/s
The USGS monitors flood and high-flow conditions at more than 300 streamgages across Montana and Wyoming. Water level and flow information are used by the National Weather Service (NWS) to make accurate flood forecasts. High-flow conditions are expressed as percentiles comparing current (within the past few hours) instantaneous flow to historical daily mean flow for all days of the year.
A percentile is a value on a scale of one hundred that indicates the percent of a distribution that is equal to or below it.
- "<95" indicates that the estimated streamflow is less than the 95th percentile for all days of the year,
- "95-98" indicates that the estimated streamflow is between the 95th and 98th percentiles for all days of the year,
- ">=99" indicates that estimated streamflow is greater than the 99th percentile, and
- "Not ranked" indicates that a flow category has not been computed. Common reasons for a "Not ranked" category are insufficient historical data or no current streamflow estimates.
Flood stages are determined by the NWS; not all USGS streamgages have flood stages. A depiction of other streamgages at or above flood stage is available the NWS River Conditions Map.
Current Flooding and High-Flow Conditions:
(Current-conditions data are provisional and subject to change)
Wyoming:
- Map: Flood and high flows
- Data table: Locations above flood stages
- Map: Current streamflow conditions vs historical streamflows
- Flood of August 1, 1985 in Cheyenne, WY
- Floods of May 1978 in southeastern Montana and northeastern Wyoming
Montana:
- Map: Flood and high flows
- Data table: Locations above flood stages
- Map: Current streamflow conditions vs historical streamflows
- Floods of May 1981 in west-central Montana
- Floods of May 1978 in southeastern Montana and northeastern Wyoming
- Floods of June 1964 in northwestern Montana
How can a 100-year flood strike twice in 15 years? This is a downloadable poster discussing the meaning and use of probability language in flood characterization.
Poster: 100-Year Flood--It's All About Chance
Below are other science projects associated with floods and high-flows in Wyoming and Montana.
Below are data or web applications associated with floods and high-flows in Wyoming and Montana.
Below are publications associated with floods and high-flows in Wyoming and Montana.
Montana StreamStats
Summary of floods in the United States during 1967
Summary of floods in the United States during 1966
Summary of floods in the United States during 1964
Summary of floods in the United States during 1963
Summary of floods in the United States during 1962
Magnitude and frequency of floods in the United States, part 6–B. Missouri River basin below Sioux City, Iowa
Magnitude and frequency of floods in the United States: Part 10. The Great Basin
Magnitude and frequency of floods in the United States: Part 6-A. Missouri River basin above Sioux City, Iowa
Magnitude and frequency of floods in the United States, part 13. Snake River basin
Floods in Wyoming, magnitude and frequency
Below are news stories associated with floods and high-flows in Wyoming and Montana.
Study Links Major Floods in North America and Europe to Multi-Decade Ocean Patterns
The number of major floods in natural rivers across Europe and North America has not increased overall during the past 80 years, a recent study has concluded. Instead researchers found that the occurrence of major flooding in North America and Europe often varies with North Atlantic Ocean temperature patterns.
The USGS monitors flood and high-flow conditions at more than 300 streamgages across Montana and Wyoming. Water level and flow information are used by the National Weather Service (NWS) to make accurate flood forecasts. High-flow conditions are expressed as percentiles comparing current (within the past few hours) instantaneous flow to historical daily mean flow for all days of the year.
A percentile is a value on a scale of one hundred that indicates the percent of a distribution that is equal to or below it.
- "<95" indicates that the estimated streamflow is less than the 95th percentile for all days of the year,
- "95-98" indicates that the estimated streamflow is between the 95th and 98th percentiles for all days of the year,
- ">=99" indicates that estimated streamflow is greater than the 99th percentile, and
- "Not ranked" indicates that a flow category has not been computed. Common reasons for a "Not ranked" category are insufficient historical data or no current streamflow estimates.
Flood stages are determined by the NWS; not all USGS streamgages have flood stages. A depiction of other streamgages at or above flood stage is available the NWS River Conditions Map.
Current Flooding and High-Flow Conditions:
(Current-conditions data are provisional and subject to change)
Wyoming:
- Map: Flood and high flows
- Data table: Locations above flood stages
- Map: Current streamflow conditions vs historical streamflows
- Flood of August 1, 1985 in Cheyenne, WY
- Floods of May 1978 in southeastern Montana and northeastern Wyoming
Montana:
- Map: Flood and high flows
- Data table: Locations above flood stages
- Map: Current streamflow conditions vs historical streamflows
- Floods of May 1981 in west-central Montana
- Floods of May 1978 in southeastern Montana and northeastern Wyoming
- Floods of June 1964 in northwestern Montana
How can a 100-year flood strike twice in 15 years? This is a downloadable poster discussing the meaning and use of probability language in flood characterization.
Poster: 100-Year Flood--It's All About Chance
Below are other science projects associated with floods and high-flows in Wyoming and Montana.
Below are data or web applications associated with floods and high-flows in Wyoming and Montana.
Below are publications associated with floods and high-flows in Wyoming and Montana.
Montana StreamStats
Summary of floods in the United States during 1967
Summary of floods in the United States during 1966
Summary of floods in the United States during 1964
Summary of floods in the United States during 1963
Summary of floods in the United States during 1962
Magnitude and frequency of floods in the United States, part 6–B. Missouri River basin below Sioux City, Iowa
Magnitude and frequency of floods in the United States: Part 10. The Great Basin
Magnitude and frequency of floods in the United States: Part 6-A. Missouri River basin above Sioux City, Iowa
Magnitude and frequency of floods in the United States, part 13. Snake River basin
Floods in Wyoming, magnitude and frequency
Below are news stories associated with floods and high-flows in Wyoming and Montana.
Study Links Major Floods in North America and Europe to Multi-Decade Ocean Patterns
The number of major floods in natural rivers across Europe and North America has not increased overall during the past 80 years, a recent study has concluded. Instead researchers found that the occurrence of major flooding in North America and Europe often varies with North Atlantic Ocean temperature patterns.