flood prediction

After a dry winter, Iowa DNR says flood risk remains high

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Image result for iowa flooding 2019
Photo from Jo Naylor, flickr

Tyler Chalfant | March 12th, 2020

This February has been warmer and drier than usual in Iowa. As a result, streamflow conditions have generally decreased, but the Iowa Department of Natural Resources says that the risk for flooding on the Missouri and Mississippi Rivers remains high for this spring. 

Though severe drought has impacted other areas of the country, there have not been drought conditions in Iowa. In total, December, January, and February saw about 3 inches of snow, which is 0.33 inches less than normal, improving stream levels across the state. 

Last year saw historic flooding in both river basins, with over 200 miles of compromised levees, and 81 of Iowa’s 99 counties put on flood warning last spring. This resulted from heavy rainfall accompanied by an unusually high amount of snowmelt from Minnesota. The Iowa Policy Project released a report warning that such flooding events are likely to become more frequent and severe as climate change makes weather patterns more difficult to predict. 

2019 was the third wettest year for the Missouri River Basin on record, meaning the basin is going into 2020 with wetter-than-normal soil. Runoff this year is expected to be more than 140% as much as normal, which would place this year in the top ten for the basin.

Iowa flooding will become more frequent and severe

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Flood 2008
Photo of 2008 flood by Jon Fravel, Flickr

Tyler Chalfant | September 10th, 2019

Iowans across the state experienced severe flooding this year, and according to a report released Thursday by the Iowa Policy Project, flooding events like those of 2019 will likely become more frequent and severe as the climate changes. While temperatures and precipitation have been shown to be rising, flooding patterns are harder to predict, but this year’s “100-year flood” seems to be the fourth flooding event of its kind in only 30 years, following severe floods in 1993, 2008, and 2011.

Both the Mississippi and Missouri River Basins flooded this year, with the Mississippi breaching a levee in Davenport, and the Missouri breaching every levee south of Council Bluffs on the western side of the state. In addition to the damage caused to flooded roads, homes, and businesses, these floods have harmed agriculture. Farmers were forced by flooded fields to plant late or not at all this year. The floods spoiled stored crops, caused the deaths of livestock, and damaged farm infrastructure. Flooding and extreme heat also pose a threat to human health through contaminated water supplies, the spread of disease-carrying insects, and harm to mental health. 

The period from May 2018 to April 2019 set new records for precipitation in the Midwest, with Iowa exceeding the regional average with over 50 inches. Since the 1970s, Iowa’s average annual rainfall has been rising by 1.25 inches per decade – the highest rate of any state in the country – and snowfall this February reached three and a half times the recent average. Springtime rainfall in the upper Mississippi is projected to increase 20 to 40 percent. The report also covered temperature increases, which are projected to be the highest in the Midwest during the warm season. 

For now, flood forecast good news

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The Iowa River in Iowa City, Iowa.
The Iowa River in Iowa City, Iowa.

The National Weather Service issued its first flood potential outlook of the year last week.

Below are locations along the Iowa River and the probability that flooding will occur between now and May 26:

  • Iowa City: Minor flooding, less than 5 percent; moderate flooding, less than 5 percent; major flooding, less than 5 percent
  • Lone Tree: Minor flooding, 18 percent; moderate flooding, 12 percent; major flooding, less than 5 percent
  • Marengo: Minor flooding, 58 percent; moderate flooding, 35 percent; major flooding, less than 5 percent

However, experts are closely watching the frost depth of the ground as spring rains near.

For the full story, click here.

Previously condemned streamgages receive funding

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USGS employees checking a streamgage. Photo by U.S. Geological survey; Flickr.
USGS employees checking a streamgage. Photo by U.S. Geological Survey; Flickr.

After the U.S. Geological Survey National Streamflow Information Program (NSIP) suffered budget cuts, three Iowa streamgages were to be shut down. However, after funding was provided by a new partner, two will continue to function. Continue reading →