A researcher at Washington University in St. Louis says the flood control systems along the Missouri, Mississippi, and other rivers in the Midwest are based on flood height estimates that are too low.
Geology Professor Robert Criss says that miscalculation means federal agencies are underestimating how high a 100-year flood on those rivers can be. A flood that reaches even a few inches above the top of a 100-year levee could cause a major breach in a flood control system, says Criss.
He says the formulas used to predict how high 100-year events could get assume conditions are the same as they were decades ago when there were fewer man-made structures along the rivers and global weather patterns weren’t changing.
“For example, the official calculations would suggest that at St. Louis since 2008 we’ve had three, 10-year floods, the most recent of which was last week. I’m saying in that period of time since 2008 we’ve had one, 5-year flood,” said Criss. “We overuse these terms – 100-year flood, 200-year flood, and so forth. They’re clearly out of whack with what is really happening. That’s because the levels we need to expect are higher than the official calculations.”
He says man-made river control systems narrow channels and keep floods from reaching wetlands and flood plains.
“We should leave our rural areas alone. We should leave our flood plains open to agriculture and not to commercial development, which is just putting more infrastructure in harm’s way while we’re aggravating the flood phenomena itself by restricting the floodwater’s access to flood plains,” said Criss, “which is what we do when we try to levee these areas off and change them from agricultural and wildlife uses to other uses.”
He says miscalculations mean 100-year levels predictions are too low in several Midwestern cities and towns along the Missouri, Mississippi, Ohio, and Illinois rivers. He says those cities’ flood protection systems should be adjusted to prepare for higher crests.
“I think we should have more realistic flood estimates … We need to build our structures and protect our cities to accommodate those rising levels, and we need to have our future land use decisions accommodate what’s really good land use for low-lying areas,” said Criss.