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How overbuilt levees are raising flood risks in northeast Missouri

The Sny Island Levee System in Illinois is one of 10 levee systems that have exceeded their authorized heights, according to a survey conducted by the Army Corps of Engineers' Rock Island District this year.
Eli Chen | St. Louis Public Radio
New data from the U.S. Army Corps of Engineers shows that floodwaters would rise the highest in the Pike County, Missouri, area due to the overbuilt levees in the Sny Island Levee Drainage District.

Data from the U.S. Army Corps of Engineers are supporting northeast Missouri residents' suspicions that overbuilt levees along the Upper Mississippi River have led to increased flooding for vulnerable communities. 

The Corps of Engineers last spring surveyed levee heights in the Rock Island District, which runs from Keokuk, Iowa, to Thebes, Illinois, and discovered that 40 percent of the levees exceeded regulation. The federal agency released a model at the end of January that measured the impact the overbuilt levees have on river flooding. The model, however, requires an experienced engineer to operate, so environmental advocacy group American Rivers hired a consultant to do so this month.

The Corps of Engineers' model revealed that some areas, such as Pike County and Hannibal, would suffer the worst raises in floodwaters if it were to face another event like the Great Flood of 1993.

Pike County would see the "largest changes" in flood levels because of the raised levees in the Sny Island Levee Drainage District in Illinois, said Jonathan Remo, a geography professor at Southern Illinois University-Carbondale who conducted the research independently for American Rivers. 

"They could see anywhere between about a half foot and 1.7 feet higher water surface in the river channel than there would normally be if the levees were at their approved heights," Remo said. 

The U.S. Army Corps of Engineers surveyed 28 levee districts in the Rock Island District. The agency found that 40 percent of the levees studied exceeded their authorized heights.
Credit The US Army Corps of Engineers Rock Island District
The U.S. Army Corps of Engineers surveyed 28 levee districts in the Rock Island District. The agency found that 40 percent of the levees studied exceeded their authorized heights.

Levee and drainage districts, which manage levees, will build them higher to protect properties and assets from flooding. Research has shown that tall levees can constrict rivers and divert water into communities that have lower levees, or weaker protection, against flooding. Some residents in Lincoln, Pike and St. Charles have organized into a group called the Neighbors of the Mississippi to call for reduced levee heights because of the adverse effects that severe and frequent flooding has had on farmland, businesses and communities. 

The region has seen multiple floods in the last decade, said Al Murry, Pike County's emergency management director. 

"The bigger events are more severe," Murry said. 

Environmental regulators in several states are working with environmental groups, engineers and other stakeholders todevelop a plan to address flood risk along the Upper Mississippi River. Some, such as the Upper Mississippi, Illinois and Missouri Rivers Association, which represents the interests of some levee and drainage districts, believe the solution lies in building more levees and hard infrastructure to help the frequently flooded communities. 

"We would argue that infrastructure should be in place throughout the entire Upper Mississippi, and that we all need to work together towards a plan that gets us there," said Aaron Baker, executive director of UMIMRA. 

Mike Reed, superintendent at the Sny Island Levee Drainage District, wrote in an email that the district and other levee officials in the country aim to responsibly help communities protect themselves from life-threatening flooding.

"This multi-state group of officials have been, and always will be, focused on what actually happens when the rains come," Reed wrote, "and [the group] will always prioritize the safety and security of families living within the levee districts over the hypothetical theories and agenda-driven academics and others for whom the levees are just a distant distraction."

Illinois and Missouri drainage districts have been secretly lobbying the Corps of Engineers to weaken levee regulations, a joint investigation by ProPublica, The Center for Investigative Reporting and The Telegraph revealed today.  

However, building taller levees could encourage a phenomenon known as "levee wars" where one property owner builds a levee to fend off diverted floodwaters caused by another raised levee. Some residents on the Missouri side are concerned that levees could get taller on the Illinois side, as the Illinois Department of Natural Resources continues to consider deregulating oversight of high levees.

"The higher you build, the higher the next guy has to build, and then that puts it back to you, and you have to do it again," Murry said. "There is no end to it." 

Follow Eli on Twitter: @StoriesByEli

Eli is the science and environment reporter at St. Louis Public Radio.