Risk of spring flooding in Eastern Iowa close to normal, forecasters say

Report: Iowa River has a 58 percent chance to reach its 14-foot flood stage in Marengo

Orlan Love
Published: February 21 2014 | 4:00 am - Updated: 29 March 2014 | 3:58 am in
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The spring flood potential for Eastern Iowa rivers is “generally near to slightly below normal,” the National Weather Service Quad Cities office said Thursday in its first flood outlook of the season.

The forecast takes into account winter precipitation, river levels, soil moisture and the depth of frost in the ground.

Hydrologist Maren Stoflet, the author of the report, said soil moisture is below normal, stream levels are near to below normal and precipitation has been variable but close to normal.

In Cedar Rapids, the likelihood of the Cedar River reaching the 12-foot flood stage is 20 percent, slightly less than the normal 23 percent, the Weather Service said.

Craig Hanson, maintenance manager for the city’s Public Works Department, said he sees little short-term risk of flooding in Cedar Rapids.

“Most Cedar Rapids floods have been caused by heavy rains rather than snowmelt,” he said.

The Iowa River at Iowa City has a less than 5 percent chance of reaching its 22-foot flood stage this spring, slightly below the normal 6 percent chance, the report said.

The report pegs one of the highest likelihoods of reaching flood stage in Eastern Iowa at Marengo, where the Iowa River has a 58 percent chance to reach its 14-foot flood stage – still well below the 72 percent chance of reaching that level in a normal spring.

“Deeply frozen soils across Eastern Iowa,” the report said, “will be a factor to watch as snowmelt and rainfall on frozen ground will run off quickly.”

State Climatologist Harry Hillaker said Department of Transportation sensors have detected frost depths of 5 feet in Cedar Rapids and 5 ½ feet in Plainfield and Cedar Falls.

“It will go deeper before it thaws,” he said.

Hillaker said snowfall in Eastern Iowa has been well above normal this winter, totaling more than 50 inches in Waterloo and Dubuque. But the generally light, dry snow remaining on the ground has a moisture equivalent of about 2.5 inches, which he termed slightly higher than average.

Snow water amounts range between 2 and 3 inches across southern Minnesota and Wisconsin, as well as northeast Iowa, according to the Weather Service office in La Crosse, Wis.

The report assesses near normal spring flood risks for the Wapsipinicon at Independence and Anamosa and for the Maquoketa River at Manchester.

Flood risks are above normal along the Mississippi River in Eastern Iowa, the La Crosse office said.

At McGregor, for example, there is a 73 percent chance the river will reach minor flood stage, which compares with the normal risk of 49 percent. Comparable risks are 60 percent at Guttenberg (normal, 47 percent), 69 percent at Dubuque (normal, 49 percent) and 38 percent at Bellevue (normal, 33 percent).

The risk of flooding from late winter into spring in central Iowa is near normal, according to the National Weather Service in Des Moines.

The NWS office in La Crosse said the flood potential for northeast Iowa may be a little below normal this spring.

The risk of the Turkey River reaching its 12-foot flood stage at Elkader was pegged at 32 percent, well below the normal 50 percent, and the risk of the Upper Iowa at Decorah reaching its 12-foot flood level was rated at the spring normal of less than 5 percent.

Climate models suggest that spring temperatures will remain below normal, delaying the snowmelt, while northwest winds aloft will likely result in near to below normal precipitation through late February and early March, the La Crosse office said.

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