A flood of concern

Font Size:

By Thomas Geyer | Monday, March 12, 2007 12:04 AM CDT | () comments

(Larry Fisher/QUAD-CITY TIMES) A fisherman heads out on the Mississippi River from the Marquette Street boat ramp in Davenport. Levels on the Mississippi in the Quad-Cities are about normal for this time of year, but that could change due to rapid snowmelt this weekend in Wisconsin.

About the map: As a general rule, 10 inches of snow is equivalent to 1 inch of water, said Bill Nichols of the National Weather Service, Davenport. However, that can vary depending upon the temperature when the snow falls, and how it compacts over time due to gravity. “We average 12-14 inches of snow per 1 inch of water here in the Quad-Cities,” he said. If it is very cold outside when the snow is falling, the ratio can be as high as 20 inches of snow to 1 inch of water, he added.

More than two feet of snow fell in the upper Mississippi Valley within the span of a week, increasing the chance of Mississippi River flooding at the Quad-Cities.

But the threat has risen only to 30 percent, still below average, the National Weather Service, Davenport, reported.

But minor to moderate flooding is possible this week for the Wapsipinicon, Cedar, Iowa and Rock rivers as higher temperatures cause the snow in northern Iowa and central and southern Minnesota and Wisconsin to melt at a faster rate.

“The probability for flooding on the Mississippi River at the Quad-Cities was 10 percent in our first spring flood outlook,” Weather Service meteorologist and hydrologist Jeff Zogg said.

But heavy snowfall up north from two storms that rolled through the Midwest on Feb. 24 and March 1 dumped as much as 20 to 30 inches of snow and changed that outlook, he said.

It is the smaller rivers and tributaries that likely will see minor to moderate flooding as early as this week, Zogg said in the latest flood outlook issued late last week.

Several things saved the

Mississippi River, which has some room to rise, he said.

First, since all that snow fell, it has been melting relatively slowly, which is critical, he said, adding that a good warm up is going to occur in the region over the next few days.

Also, most of the snow that fell was over bare ground, he said, which means the snow pack is not over as broad an area as it has been in years past.

“Also, the water equivalent of the snow is less than we thought, which also has reduced the chance of Mississippi River flooding,” he said.

Strangely, enough, he added, the area of the headwaters of the Mississippi River is suffering from a drought.

The chance for minor to moderate flooding on the Wapsipinicon River at DeWitt, the Cedar River at Conesville and the Iowa River at Wapello and Columbus Junction is 90 percent, according to Zogg’s latest flood outlook. The Rock River at Moline and Joslin has a 60 percent to 70 percent chance of flooding.

“Because the rivers were already normal to above normal, that water coming down from northern Iowa and Minnesota is likely going to cause some flooding,” Zogg said. “That could occur (this) week.

“But just because the probability for flooding is high does not mean we’re going to have significant flooding. In most cases, it won’t be that big of a deal, minor to moderate at worst, but it is still flooding nonetheless.”

Another critical element saving the Quad-Cities from significant flooding is the lack of rainfall northward, said Terry Swails, chief meteorologist at KWQC-TV6.

“I don’t see any indications for a major storm for the next seven to 10 days,” Swails said.

He said that early this week, the region will see nighttime temperatures above the freezing mark, which will speed the thaw.

“The best scenario is thawing during the day and freezing at night,” he said. “That’s what you like to see if you don’t want a flood.”

Getting rid of that snow pack before spring rains will also lessen chances for flooding in April and May, Swails said.

As long as something major doesn’t develop within the next two weeks, he said, there should not be any major problems.

“We can take the minor flooding.” Swails said.

With planting season about six weeks away, farmers say that soil moisture levels are excellent and that a little dry weather while planting will keep the soil from being compacted by the heavy planting machines.

“Ideally, we’ll start planting some time between April 15 and then end of April,” said Taylor Ridge, Ill., farmer Tom Mueller, who is the president of the Rock Island County Farm Bureau.

“We need to let the fields dry out some and allow the soil to warm up,” he said.

Thomas Geyer can be contacted at (563) 383-2328 or tgeyer@qctimes.com.