The Meramec River is expected to crest at 40 feet on Wednesday, posing a threat to low-lying communities, including Valley Park, Eureka, Fenton and Kirkwood.

As water levels rise along the same communities that were badly impacted by flooding in early 2016, some local environmentalists say that levees are responsible for the severe floods residents in the St. Louis area have experienced in recent years.

"The more we wall the rivers off and constrict them with levees and river structures, the flood levels themselves get aggravated," said Bob Criss, a hydrogeologist at Washington University in St. Louis. "That's what we're seeing around Valley Park."

Last year, an engineering firm published a study that found that the Valley Park levee could have been overbuilt by as much as eight feet, making it a 500-year flood levee. Valley Park's levee was only supposed to be built to the 100-year flood level.

Army Corps of Engineers officials maintain that the structure is still compliant with regulation. But Criss and others say the levee diverted water to neighboring communities and damaged them, while leaving Valley Park mostly dry.

Manmade structures and human development along the rivers in the St. Louis area have made flooding worse in recent years, said David Stokes, executive director of the Great Rivers Habitat Alliance.

"We should be planning to get lots of rain at certain points," Stokes said. "And we should be leaving our floodplains undeveloped so that creeks and small rivers and large rivers can go where Mother Nature intended."

The Corps of Engineers began surveying the heights of 50 levees in the St. Louis district last October. They expect to finish and release findings by next March.

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