Flood Season Begins Unusually Early Across Heartland

Illinois got its first floods in January, earning federal disaster designation for several counties. Ice jams, formed when floes collide and block a river's flow, also caused flooding in the Quad Cities area in the winter.

National Weather Service hydrologist Noreen Schwein said the recent flooding has been caused by large frontal low-pressure systems, more common in fall and winter, that linger over a region for long periods.

"In spring, we'll transition to more severe weather systems that move through more rapidly," she said. That likely means fewer consecutive days of rain in one place, but the deluges can still cause serious flooding.

For cities in the Great Lakes region, flooding often results in untreated sewage overflowing into rivers and the lakes.

"With spring rains, we will see overflows everywhere in the region," Jeff Skelding of the National Wildlife Federation said. The federation is part of a coalition seeking federal funding to help municipalities overhaul aging, overburdened sewer systems. "It's a problem for public health, for beaches. It's a chronic problem in the Great Lakes that's not going to go away without congressional action," Skelding said.

The National Weather Service has tried to prepare the public, holding a flood safety awareness week March 17-21 and, among other things, urging people to "turn around, don't drown" when they come to flooded roads.

"Flooding causes more deaths than any other weather phenomenon," Weather Service spokesman Patrick Slattery said. "A lot of people take on low water crossings thinking they will be fine and then find out they're not."

Because floodwater from the Midwest and Ozark regions ends up in the Mississippi River, the March floods and more spring flooding could also put the Katrina-ravaged Gulf Coast at risk. Currently, the Mississippi is so swollen that officials are considering opening the Bonnet Carré Spillway for the first time since 1997 to divert water from the Mississippi into Louisiana's Lake Pontchartrain.

Trenberth said heavier flooding is one of the widely predicted effects of global warming, because higher ocean temperatures mean the air can hold more moisture for storms to draw from.

"When it rains, it pours, and even when it snows, we will get heavier snowfalls," Trenberth said. "Whether that converts to flooding depends on what mitigation factors have occurred on the ground."