2011 National Hydrologic Assessment – Spring Flooding Alert

Key Points

  • Conditions are favorable for spring flooding over large sections of the United States, from the Northern Plains through the Midwest and eastward to New England.
  • A large swath of the north central United States is at risk of moderate to major flooding this spring.
  • National Weather Service models show this year’s snowpack contains a water content ranked among the highest of the last 60 years, which is similar to the past two years.
  • For the third consecutive year, forecasters predict major flooding along the Red River of the North, which forms the state line between eastern North Dakota and northwest Minnesota. Other areas of the Midwest primed for major flooding include Devils Lake in North Dakota, the Milk River in northeastern Montana, the James and Big Sioux Rivers in South Dakota, the Minnesota River, and the Mississippi River from its headwaters near St. Paul, Minnesota, downstream to St. Louis.
  • Recent heavy rains across the Ohio Valley have saturated soils and have rivers running high. With the forecast calling for above average precipitation during the next two weeks, the flood threat for this area has been raised to above average.
  • The Lower Mississippi River now has an above average risk of flooding due to the recent rains across the Ohio Valley adding additional volume of water to the Mississippi River.
  • Much of the Northeast has an above average risk of flooding with the highest risk in portions of southeastern New York, eastern Pennsylvania and northern New Jersey.
  • Mid-March is too early to determine spring flooding potential across the western United States.

Specific Flood Risks

North Central United States and Upper Mississippi River

Heavy late summer and autumn precipitation left soils saturated and streams running high before the winter freeze-up. A large portion of the north central United States at risk of moderate to major flooding this spring, extending from northeastern Montana through western Wisconsin and along the Mississippi River, south to St. Louis. A series of storm systems are forecast to move across the region during the next two weeks, which could bring additional snow or rain on top of the remaining snowpack. These systems may cause substantial runoff and the beginning of minor flooding in the southern headwater portion of the Red River of the North, eventually leading to major flooding sometime from the last week of March through early April.

Along specific rivers:

  • The Red River of the North:
    • Fargo, North Dakota, has a near 95 percent chance of exceeding major flood stage of 30 feet, and about a 35 percent chance exists of reaching or exceeding the 40.8 foot record set in 2009.
    • Grand Forks, North Dakota, has about a 95 percent chance of exceeding major flood stage of 46 feet.
  • On Devils Lake, North Dakota, there is approximately a 25 percent chance of exceeding 1,455 feet, which could partially inundate portions of the town of Minnewauken.
  • The Milk River and its tributaries in northeastern Montana, there is potential for moderate to major flooding .
  • The James River at Huron, South Dakota, has about a 95 percent chance of exceeding major flood stage of 15 feet and a 25 percent chance of exceeding the record 21.2 foot level set in 1997.
  • The Big Sioux River at Brookings, South Dakota, has a greater than 95 percent chance of exceeding major flood stage of 12 feet and about a 50 percent chance of exceeding the 14.77-foot record set in 1969.
  • The Mississippi River is likely to see major flooding beginning in late March from its headwaters near St. Paul, Minnesota, downstream to St. Louis.
    • St. Paul, Minnesota, has about a 95 percent chance of exceeding major flood stage of 17 feet, where secondary flood walls are deployed to protect the St. Paul Airport.
    • Further downstream, there is a 75 percent chance for major flooding on the Upper Mississippi River from Winona, Minnesota, to Keokuk, Iowa.

Ohio River Valley
There is currently an above average risk of flooding in the Ohio River Valley, primarily in the Wabash and White river basins. February rain and snowfall  was above normal with many portions of the region receiving over 200 percent of normal precipitation. Since March 1st, this region has received nearly 400 percent of normal precipitation much of which has already caused flooding.

Lower Mississippi River
This spring, as flood waters drain from the Upper and Middle Mississippi and Ohio Rivers, the flood threat downstream to the Gulf of Mexico will increase.  Despite dry conditions through much of the Gulf Coast over the winter, the Lower Mississippi River now has an above average risk of flooding. Recent snowmelt and rains across the Ohio, Cumberland and Tennessee Rivers are currently producing moderate to major flooding on the Lower Ohio River and Mississippi River above Memphis, Tennessee. 

Northeastern United States
Most of the Northeast has an above average risk of flooding as a result of above average snowfall this winter, followed by recent heavy rains. With the spring melt underway, and soils already saturated region-wide, any additional heavy rainfall will greatly elevate flood risk. The highest risk of flooding is currently centered over southeastern New York State, eastern Pennsylvania and northern New Jersey, but other areas may be added to the list as future storm systems impact the area. 

Links for additional information

 

Advertisements

Comments are closed.