It was a fairly new concept for federal policymakers in the early s, but by the time the levee was complete, scientists were highly confident that human-driven climate change would affect rainfall all over the country. But climate change makes everything more unpredictable. The Corps now considers climate change in some of its flood planning, but an Obama-era executive order that might have strengthened its approach was rescinded last year by President Donald Trump.
The Corps never updated its calculations or checked them for accuracy—not when levee construction wrapped up in , nor when the levee held back its first big flood in or after the larger, more recent floods. The Corps used widely available modeling software of the early s.
As a result, levees that are meant to last for decades, even a century, are built based on maps and modeling technology from another era. The Valley Park levee met its first test when floods tore through the Midwest in spring Lewis Setliff declared. But upstream in Pacific, the mood was grim. More than buildings flooded. Then-Mayor Herbert Adams urged federal officials to provide a levee or some other protection for communities along the Meramec.
And at least one resident wasted no time assigning blame. The record floods in and only fed the suspicions in neighboring towns. Was the levee to blame? The Corps defended its work with a fact sheet citing its calculations from , but no new data. John Boeckmann, the Corps engineer, said development in the area makes it hard to assess. The St. Louis District alone has more than 70 levees, so the costs soon would add up to millions of dollars. Such a study could even help the Corps make better predictions.
But there are built-in disincentives for the Corps to prove its own work was wrong, Remo said. It could expose the agency to litigation. Anne Jefferson, a geology professor at Kent State University, said it all comes down to funding priorities. Researchers say this is a common problem in science and engineering. The federal government has the tools to get a much better picture of how levees worsen flooding, for a fraction of the cost of a comprehensive model.
The US Geological Survey, a scientific agency that monitors natural hazards, operates stream gauges that measure the flow of water in rivers. In , two scientists used stream gauges next to or directly upstream of levees to examine water heights during floods, as well as flow rates—the amount of water rushing past the gauge each second.
The higher the flow rate, the larger the flood. The scientists studied 13 levees in the Midwest, compiling these two measurements before and after the levees were built. They wanted to see whether floods with similar flow rates produced different flood heights before and after levee construction. They found that in all 13 cases, for floods of the same flow rate, water heights post-levee were higher than pre-levee—in one instance by more than 5 feet.
But the Geological Survey and other agencies have struggled to maintain their network of gauges. Due to tight budgets, the Geological Survey said only 73 percent of the gauges it considers essential for monitoring rivers are operational today. Bob Criss, an earth science professor at Washington University in St.
Louis, tried to do a stream gauge analysis for Valley Park, but the limitations of the gauges led him astray. Correcting that data made the extra height disappear.
The Geological Survey acknowledged this shortcoming to reporters after the flood. Six months after the Criss paper, a separate report found that the levee must have been higher than its authorized height, because at the year flood level, it would have been submerged in , which would have lowered the water level in nearby towns.
The report was funded by the Great Rivers Habitat Alliance, which had hired a local engineering firm to measure the height of the levee at several locations. When the agency designed the levee, it modeled the size of the year flood at Valley Park and found the baseline levee height needed to hold back that flood.
Then the Corps added an extra 3 feet to the levee design for safety and up to 4 feet more to account for how the levee might settle over time.
That meant the levee was built up to 7 feet higher than the elevation of the year flood. For Valley Park, the added height makes it virtually certain that the city will be protected from a major flood, even if its flow rate is larger than what the Corps calculated in And just like the Army Corps, they have little incentive to do anything that might indicate their levees are piling extra harm onto surrounding communities.
Rydlund said he hopes such a study could help people on the river understand its changing behavior. Samantha Medlock of the Association of State Floodplain Managers agrees, stating "Ultimately this is about protecting people permanently. No levee provides permanent or complete protection. Buying out and relocating to higher, safer ground is permanent protection. Terms of Use Privacy Policy.
Anacostia Watershed Society is a certified, nonprofit, tax-exempt charitable organization tax identification number under Section c 3 of the Internal Revenue Code. Donations are tax-deductible as allowed by law. To Levee or Not to Levee? Levee inspectors also look for signs of erosion, rutting or other pits that might indicate drainage problems.
They look for cracking, slope stability, and signs of unwanted vegetation or animal burrowing. Conforti, the Levee Safety program manager for the U. Army Corps of Engineers, in a statement provided by a spokesman. New Orleans now claims to have the best flood protection of any coastal community in the United States. Just as important, it was designed to be a true system, and not just a system in name only as its predecessor.
That may be true. When dozens of levees catastrophically failed throughout New Orleans in , the strength of the storm surge was only partly to blame. All of a sudden, I push on the top of my piece of cake, and what it's moving on is this weak, slick icing. The whole thing moves. Katrina left some 80 percent of the city flooded, with sections of New Orleans under 20 feet of water or more. The reporting , which was based on findings of the Army Corps of Engineers, suggests that areas unprotected by levees might be bearing the brunt of the redirected waters.
Even if exacerbated by climate change, spring floods wouldn't be as serious of a problem if local governments hadn't allowed development in vulnerable floodplains, Criss said. We know where these low-lying areas are. And yet we seem to insist on building levees and thinking that developing in these low-lying areas is OK. And it's not OK. Noah Diffenbaugh, a professor of earth system science at Stanford University, was the lead author of a study in Proceedings of the National Academy of Sciences released last week detailing a four-step framework for testing whether global warming contributes to record-setting weather events.
Climate change means communities must re-evaluate hazards, exposure and risk, said Diffenbaugh. We have a lot of opportunity to catch up with the climate change that's already happening, and prepare for the climate of the future.
In Cape Girardeau, which sits behind a flood wall that runs more than a mile along the river, Mayor Harry Rediger sees the barrier as a requirement for living along a mighty waterway — even as he acknowledges that it'd be near-impossible to get the funding for such a project today. Finished in , the wall is designed to withstand floods up to 55 feet. So far, the highest floodwaters seen in Cape Girardeau came last year, when waters crested after a December storm at The most recent floodwaters, expected to go down in the history books as the sixth highest in a city that dates to , crested at Schaaf and his family live on the edge of the city's Red Star neighborhood north of the flood wall.
His family lives on a hill, but the sloped, lower part of their backyard is vulnerable to flooding. They had to fight to get into a lower flood-insurance premium category by proving that their home was at higher elevation than the flood-prone lower yard, said Schaaf. Over time, the city has bought out many of the lower-lying homes, and would like to buy out more in the neighborhood, Rediger said.
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