Despite melt, Eastern Iowa's flood risk has increased

CEDAR RAPIDS – Despite the recent gradual melting of the heavy winter snowpack, the risk of spring flooding along Eastern Iowa rivers has increased slightly in the past three weeks, the National Weather Service said today in its second spring flooding outlook of the season.

Since the first report on Jan. 27, “we had the early February blizzard and additional snows in Minnesota and Wisconsin,” which added to the moisture available for flooding, said meteorologist Brian Pierce at the Weather Service's Quad Cities office.

The service, in its Jan. 27 report, rated the risk of Cedar River flooding this spring at 16 percent greater than normal at Vinton and 17 percent greater than normal at Cedar Rapids. In its report released Thursday, those numbers had climbed to 19 percent and 25 percent, respectively.

A year ago the spring flood risk for the Cedar River at Cedar Rapids was rated 69 percent greater than normal.

For the Maquoketa River at Manchester, the new report indicated a 27 percent greater than normal chance that it would reach the 14-foot flood stage – up from 25 percent in the year's first report.

The flooding outlook along the Iowa River at Iowa City was listed as “near normal” in both reports. Last year at this time, the Weather Service rated the spring flood risk on the Iowa River at Iowa City at 26 percent greater than normal.

“That's welcome news,” said Iowa City Public Works Director Rick Fosse. While the city is moving forward on long-term flood mitigation projects, it has made no unusual preparations for potential flooding this spring, he said

“I'm feeling really good compared to a year ago,” said Coralville Lake operations manager John Castle with the Army Corps of Engineers.

A year ago, he said, the Corps had already begun drawing down the lake in anticipation of spring floods. This year the drawdown – which will drop the lake from its current 684 feet to 679 feet – won't begin until the middle of next week, he said.

Pierce said the recent thaw started under ideal conditions last weekend with sub-freezing nighttime temperatures but has accelerated with unseasonably warm weather through the middle of this week

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At first, he said, the melt water soaked into the ground, but now it is starting to collect in streams. Area rivers are starting to rise, with the Cedar at Cedar Rapids climbing about a foot since Monday, he said.

Craig Hanson, who coordinates flood management for the Cedar Rapids Public Works Department, said local snowmelt presents more of a flood threat on area creeks than on the Cedar River.

“Rainfall gives us river flooding, and that's difficult to predict in advance,” he said.

At noon Thursday the English River at Kalona stood at 15.78 feet, almost 2 feet above flood stage, but it was expected to fall later this week. The Iowa River at Marengo was approaching the 14-foot flood stage on Thursday and was expected to crest around 15 feet later this week. The Iowa River near Lone Tree stood at 14.04 feet at noon Thursday and was expected to crest just below its 15-foot flood stage on Friday.

“At this time, there is nothing to worry about with the rising river levels in Eastern Iowa,” Pierce said.

Longer term, heavy amounts of snow remaining on the ground in northern Iowa, southern Minnesota and western Wisconsin could present problems, he said.

That snow “has extremely high water content, and soil moisture in those areas is near record levels,” he said.

The National Weather Service at La Crosse, Wis., which monitors stream conditions along the Upper Mississippi and a few northeast Iowa tributaries, said “not much has really changed in the flooding potential across the region” since its late-January report.

While recent mild weather has shrunk the snowpack, “the amount of water in that snow cover remains relatively high,” the report said.

The chance of the Turkey River flooding at Elkader and Garber and the Upper Iowa flooding at Decorah was in the near normal range, according to the report.

Flood risk on the Mississippi ranged from 49 percent greater than normal at McGregor to 68 percent greater than normal at Lansing.