Three years on, New Orleans still makes headlines for the havoc wreaked by Hurricane Katrina, which caused about $400 million in infrastructure damage. Yet 1,000 miles north, on the usually quiet banks of the Cedar River in the usually quiet city of Cedar Rapids, Iowa, summer floods are racking up even higher damage estimates approaching $570 million.
So as New Orleans continues its much-publicized rebuilding process, Iowa's second-largest city has begun its own, much-less-heralded rebuilding process.
Ironically, Cedar Rapids officials had dubbed 2008 the “Year of the River.” But riverfront redevelopment plans were all but lost when the second snowiest winter on record gave way to an unusually rainy spring.
By the end of June, average rainfall statewide was 23.8 inches, setting a record for the first six months of the year. In Cedar Rapids, rain pounded already waterlogged areas; some sections got 6 inches on June 12 alone, one day before the river crested at 31.12 inches.
“The June 13 flood event was actually the second major flood in Cedar Rapids this year,” says Public Works Director Dave Elgin, PE. “The rains were following the crests, which progressively increased the depths of the crests downstream.”
Because spring floods frequently occur throughout the Midwest, many river cities combat this natural event with a systematic program in which just about any water depth has a counter measure.
“We consider it a methodical engineering response,” says Craig Hanson, PE, Cedar Rapids' public works maintenance manager. “We have a flood program manual covering lessons learned from the previous 150 years of flooding.” The manual was formalized by city staff and the public works department from a series of flood summary documents generated in 1993, when the Cedar River crested at just above 19 feet.
The manual, which includes personnel assignments, is revised yearly. “We conduct annual flood training for all public works personnel in early March because the earliest historic major flood occurred March 16 and 17,” Elgin adds.
This year, at least initially, this systematic approach worked as planned. But as the rain continued, water levels soon surpassed the program's limits.
In late April, the river crested at 17 feet. Working from the manual's historical data, public works crews plugged select storm sewers and placed pumps in low-lying areas to avoid sewer backups. The efforts worked.
But by June, ever-changing crest projections were hampering mitigation efforts.
Typically, the Cedar River slowly meanders through downtown Cedar Rapids at depths of less than 8 feet. With a flood stage of 12 feet and major flooding at 16 feet, the 100- and 500-year floodplains are set at 22.5 and 26.5 feet, respectively.
A week before the peak crest, projections were approximately 18 feet, so the department followed manual procedure for that flood stage and began evacuating low-lying areas. “We're the trigger mechanism for local law enforcement's reverse 911 system,” Hanson says.