Flood risk rising for Cedar River; Corps dropping Coralville Lake level early

The risk of the Cedar River flooding here this spring has increased dramatically in the past three weeks, according to a flood forecast released today by the National Weather Service.

Three weeks ago the service pegged the spring flood risk at Cedar Rapids at 33 percent greater than normal. The comparable figure today is 69 percent.

The liquid content of the snowpack and elevated river and soil moisture levels are the chief factors contributing to the increased risk of spring flooding, the Weather Service said.

For the Cedar River at Cedar Rapids, the report projects a 90 percent greater than normal chance of minor flooding, a 70 percent greater than normal chance of moderate flooding and a 41 percent greater than normal chance of major flooding.

The comparable numbers three weeks ago were 50 percent, 29 percent and 16 percent, respectively.

The comparable percentages in February 2008, just months before a record Cedar River crest swamped Cedar Rapids, were 43, 24 and 13.

For the Iowa River at Iowa City, there is a 26 percent greater than normal chance of spring flooding, up from 14 percent three weeks ago.

The most tangible preparation for the increased likelihood of flooding this spring is the Corps of Engineers' decision to start lowering the Coralville Lake on Monday, rather than waiting for the ice to go out, as is the usual practice.

The lake management plan calls for starting the spring drawdown on Feb. 15, but the Corps usually waits until ice out to avoid some safety problems and to help maintain adequate dissolved oxygen levels for aquatic life.

“Due to the forecast for a greater chance of flooding, we decided to start lowering it on Feb. 15,” said John Castle, lake operations manager.

More snow is in the forecast for Iowa this weekend, raising snow totals and concerns about spring flooding across the state.

In Des Moines' Birdland neighborhood, a long-awaited levee project is at least two years away from being finished. The neighborhood was inundated with floodwaters in June 2008 after a breach in the levee.

Construction on the $8.5 million levee is expected to begin in May.

Meteorologist Jacob Beitlich says conditions haven't improved, which means Iowa needs a drier spring.

Heavy snow preceded flooding in 2008.

-- The Associated Press contributed to this story.

LINKS of interest:

LINKS of interest:

• Hydrograph information for Coralville Lake (includes access to 2008 and other historical data)
• National Weather Service flood outlook for LaCrosse, Wis.
• Talking points from the NWS' Des Moines flood outlook