Flood Watch 2014: 65 Percent Chance of Flooding this Spring in Stillwater

 

The National Weather Service released a revised spring flooding outlook last week, that says there is about a 65 percent chance of the St. Croix River reaching 687 feet this spring and pouring over its banks in Stillwater.

The average water level in Stillwater is 675 feet. The following are elevations (in feet) of various impacts due to flooding:

  • Stillwater Riverwalk becomes inundated: 678
  • Minnesota and Wisconsin may impose a no wake zone on the river: 683
  • Due to safety issues, the Stillwater lift bridge will close: 686
  • Approximate 100-year flood stage: 692.5

The latest report from the NWS shows the St. Croix River at:

  • 63 percent likelihood for reaching minor flood stage (normal is 24% for this time of year)
  • 36 percent for moderate flood stage (15% is normal
  • 20 percent for major flood stage (9% is normal).

These estimates have stayed the same since the last flood outlook report issued by the National Weather Service.

The city is moving forward to plan for flooding this spring, City Engineer Shawn Sanders told the City Council on Tuesday night.

“We have gotten quotes from a couple of contractors in case we need to move in some barriers and build a temporary dike,” Sanders said. “We are proceeding as if there will be some flooding.”

The National Weather Service predicts a crest during the second and third week of April, but a lot of that is dependent on the weather, precipitation and everything else, Sanders said. “We’ll continue to monitor the situation.”

Water Levels

The average water level in Stillwater is 675 feet. The following are elevations (in feet) of various impacts due to flooding:

  • Stillwater Riverwalk becomes inundated: 678
  • Minnesota and Wisconsin may impose a no wake zone on the river: 683
  • Due to safety issues, the Stillwater lift bridge will close: 686
  • Approximate 100-year flood stage: 692.5

Flood Categories

  • Action Stage: 680
  • Flood Stage: 687
  • Moderate Flood Stage: 688
  • Major Flood Stage: 689

Stillwater Flood History

The highest flood elevations (in feet) in Stillwater history are the following, according to the National Weather Service:

  1. 694.10 ft on April 18, 1965
  2. 692.30 ft on April 27, 2001
  3. 692.20 ft on April 16, 1969
  4. 691.10 ft on April 16, 2001
  5. 690.45 ft on April 12, 1997
  6. 689.70 ft on APril 14, 1952
  7. 687.90 ft on June 28, 1993
  8. 687.50 ft on April 6, 1986
  9. 687.30 ft on April 30, 1975

Updated FROM:

These estimates increased, according to the NWS, for a couple of reasons:

First, the recent snow storm we had left 10 inches of snow which contained about 1 inch of water. Second, because we have had below normal temperatures we have not melted any of the snow pack.

Currently the forecast is for continued lower than normal temperatures. If that holds true we will look for a gradual snow melt, which will work in our favor. Of course much will also be dependent on the amount of spring precipitation.

In some areas the frost depths are reaching depths of 8 feet. These are typically below roadways and sidewalks; the snow pack areas have frost depths of 30-40 inches.

Updated from:

Stillwater has seen plenty of snowfall this winter, but what does that mean for spring flooding?

Well, the early-prediction flood forecast for Washington County’s area of the St. Croix River is “below average,” according to the National Weather Service.  Specifically, Washington County is currently at an 11 percent likelihood of reaching the “normal flood stage.”

“February snows have added to the snowpack over eastern Minnesota and western Wisconsin, slightly raising the possibility of spring flooding in these areas,” a flood prediction forecast issued by the NWS on Feb. 20 states. “However, with the exception of the Eau Claire and Chippewa Rivers in Wisconsin, the flood probabilities for most rivers remain near to below historical averages.”

Snow depth ranges from 2-3 feet in the Stillwater area, according to the NWS, but the water equivalent in the snowpack is about 3-4 inches with frost depths between 15-30 inches across the metro, with the deepest frost depths where the snowpack is less.

But as always, the true threat lies in how fast spring heats up, and how much precipitation falls in the area.

According to the NWS, long range outlooks show a high probability of cooler than normal temperatures over the area through April, with lower than normal precipitation, which is a good thing when it comes to reducing the possibility of major flooding.

Thick layers of ice cover the St. Croix, according to the NWS, so ice jams will be a concern. The NWS will release the next flood forecast outlook in early-March.

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Quick Facts:

  • 8-10 inches of snow fell in Stillwater last week, but that equates to about .75 inch of water to the current snowpack.
  • About 1.5 – 3 inches of water equivalent has fallen in Stillwater in the last 30 days
  • For the year, about 5 – 10 inches of water equivalent is covering most of the area, which is about 110-125 percent of the norm

Water Levels

The average water level in Stillwater is 675 feet. The following are elevations (in feet) of various impacts due to flooding:

  • Stillwater Riverwalk becomes inundated: 678
  • Minnesota and Wisconsin may impose a no wake zone on the river: 683
  • Due to safety issues, the Stillwater lift bridge will close: 686
  • Approximate 100-year flood stage: 692.5

As of Feb. 20, the NWS predicts:

  • 12 percent chance of minor flooding for St. Croix River at Stillwater
  • 10 percent chance of moderate flooding for St. Croix River at Stillwater
  • less than 5 percent chance of major flooding for St. Croix River at Stillwater

Flood Categories

  • Action Stage: 680
  • Flood Stage: 687
  • Moderate Flood Stage: 688
  • Major Flood Stage: 689

Stillwater Flood History

The highest flood elevations (in feet) in Stillwater history are the following, according to the National Weather Service:

  1. 694.10 ft on April 18, 1965
  2. 692.30 ft on April 27, 2001
  3. 692.20 ft on April 16, 1969
  4. 691.10 ft on April 16, 2001
  5. 690.45 ft on April 12, 1997
  6. 689.70 ft on APril 14, 1952
  7. 687.90 ft on June 28, 1993
  8. 687.50 ft on April 6, 1986
  9. 687.30 ft on April 30, 1975

The statistics and forecasts from this article come from the Advanced Hydrologic Prediction Service provided by the National Oceanic and Atmospheric Administration‘s National Weather Service (NOAA-NWS).

 

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