About 40 percent of levees along the Mississippi River in the Army Corps of Engineers district north of St. Louis are built higher than their authorized heights, according to the agency’s own findings.

The Corps’ Rock Island District, which covers an area beginning about 60 miles upstream from St. Louis, reports that about 80 out of 202 miles of levee systems it surveyed are improperly high, based on data yet to be publicly released.

“Some of those were between 2 and 4 feet above their authorized elevation,” said Scott Whitney, the Corps’ Rock Island District flood risk manager and chief of project management. “The revelation is out there that levee districts throughout this region have taken, in some cases, some pretty extreme measures to protect themselves.”

That protection, he notes, has come “at the cost of others,” with the added levee height leaving other areas more vulnerable to redirected floodwater. Whitney said the district is still developing a hydraulic model to understand how far-reaching the levees’ combined impact on flooding has been, including whether the St. Louis area has been affected.

But the chronically overbuilt levees to the north cause some to wonder whether the problem is more widespread, rekindling some skepticism about levee heights around St. Louis. Last year, the issue gained visibility when an independent group found the levee in Valley Park, along the recently flooded Meramec River, to be as much as 8 feet higher than what was believed to be its proper height.

The Corps’ St. Louis District maintains that Valley Park’s levee is properly built and that it did not worsen local flooding in late 2015 and early 2016.

Officials confirmed, however, that they are conducting similar efforts to examine the heights of the approximately 50 federally built levees in the St. Louis district, including the one in Valley Park. The surveys began late last year and are expected to be complete by March 2018.

“It’s pretty much been a result of the ongoing controversies up north,” said John Osterhage, levee safety program manager for the St. Louis district.

Those upstream disputes about levee heights have simmered for years. Many of the Rock Island District’s levees are made of sand, making it possible for bulldozers to push them higher to ride out floods. That was the case in 2008, when a number of the region’s levee districts were allowed to temporarily make emergency modifications in anticipation of flooding.

But the structures are not always returned to their original, authorized elevations. Corps officials said mounting suspicions spurred them to resurvey the area’s levee heights.

Levee debates have been especially loud in areas next to the Sny Island Levee and Drainage District, which stretches along about 60 miles of the Illinois riverfront, from Quincy to Belleview. The Sny, the largest levee-protected area overseen by the Corps’ Rock Island office, has come under fire from government agencies and flood-damaged farmers for supposedly exceeding its authorized height.

But the numbers revealed by the Rock Island District’s newly redone surveys show that the Sny is not the lone offender. Ten systems across seven different levee districts in Missouri, Illinois and Iowa had the majority of their construction exceed the authorized design grade by more than 2 feet.

Whitney says that even some within the Corps worry that the findings could hint at a systemic problem.

“Given what we’ve observed here, it’s taken away a lot of the security that a lot of other districts have felt,” said Whitney. “While we had suspicions and had identified some issues and concerns, this survey delineated a much bigger problem.”

Those concerns are shared by St. Louis-area river and flood policy experts.

“I don’t know why the problem would be more severe in the Rock Island District,” said David Stokes, executive director of Great Rivers Habitat Alliance, an organization devoted to river management issues.

“I mean this isn’t a few inches higher,” Stokes added. “There’s definitely a problem (with) levee districts ignoring the rules.”

Osterhage, though, said the St. Louis District doesn’t “anticipate having issues to the extent that they do” upstream, explaining that many local levees are clay-based and are not reshaped prior to floods.

Levee elevations can go unchecked for years at a time. Even with federally built levees, maintenance is often left to independent levee districts and sponsors, who must apply for permits to alter the structures. The Corps conducts visual levee inspections every year, which usually consist of cursory glances from a vehicle to detect any glaring damage or levee modifications. More thorough inspections that survey height along the tops of levees are generally done every five years, Osterhage said.

Critics maintain that levee systems are a “counterproductive” tool for flood control.

“With our so-called flood prevention efforts, high levees are counterproductive, just magnifying the potential damage,” said Bob Criss, a professor in the Department of Earth and Planetary Sciences at Washington University. “The water’s gotta spread out.”

Some argue that reliance on levees should be diminished in the long run, but that more immediately, the structures should be subject to better enforcement, since coordinating heights with other levees is essential.

“If levees aren’t at the heights they’re approved for, then nobody else knows how to plan,” said Stokes, adding that the Corps or other regulatory agencies must compel them to come down to their proper elevation.

But levee districts have shown an unwillingness to comply. Whitney said only one of the levee districts recently found to exceed its authorized height has so far cooperated with the Corps in trying to discuss a solution. The rest, he said, are reluctant to go through the procedure.

Complicating matters further, stronger flood protection is increasingly coveted, with an unusual number of major floods taking place in recent years — a symptom consistent with more erratic trends in precipitation predicted by climate change.

“We’re in an extremely wet period,” said Whitney, noting that several of the region’s top flooding events on record have occurred in the last decade. “We’ve had a number of those in the last several years. People think, ‘My God, I’ve had three 100-year flood events in the last five years.’”

Bryce Gray • 314-340-8307

@_BryceGray on Twitter

bgray@post-dispatch.com

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