"Too Much Engineering Has Made Mississippi River Floods Worse"

"Scientists, environmentalists, and anyone who lives within a hundred miles of the winding Mississippi River will tell you—have told you, repeatedly, for 150 years—that efforts to tame the river have only made it more feral. But scientists would like more than intuition, more than a history of 18th-century river level gauges and discharge stations, more than written and folkloric memory. They would like proof.

Luckily, rivers inscribe their history onto the landscape. Which is why Samuel Muñoz, a geoscientist from Northeastern University, found himself balancing on a pontoon boat with a hole in the middle, trying to jam 30 feet of aluminum irrigation pipe into the muddy bottom of a 500-year-old oxbow lake. Muñoz and his team thought that if they could just pull up good cores of that mud, the layers would be a chronology of forgotten floods—a fossil record of the river’s inconstancy made not through petrification but implication.

Basically, the Mississippi meanders. Sometimes the river curves around so tightly that it just pinches off, cutting across the peninsula and leaving the bigger curve high, if not dry. That parenthesis of water alongside the main channel is an oxbow. In a flood, water churns up chunks of sediment and spreads into the oxbow. When the flood waters recede, the layer of coarse sediment sinks to the oxbow’s bottom, where it remains."

Adam Rogers reports for Wired April 4, 2018.