Flood thy neighbor: Who stays dry and who decides?

all, making them useless for these calculations.

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. He co-wrote a paper on the 2015 flood and called it a “man-made disaster.” It blamed the levee and other upstream development for raising water levels at Eureka a foot higher than they should have been. What Criss didn’t realize — and what ProPublica and Reveal have only recently discovered — is that the underlying data was flawed because the Geological Survey had moved the stream gauge several months before the flood, without flagging the change in the data.

Correcting that data made the extra height disappear. Whatever the impact from the Valley Park levee and nearby development, it wasn’t great enough to reach the Eureka gauge.

It’s also impossible to use gauges to measure flooding from the Valley Park levee, because the gauge next to the levee measures only water heights. The Geological Survey acknowledged this shortcoming to reporters after the 2008 flood. In 2015, the river at Valley Park rose higher than it had in 1982 — but without knowing the flow rate, it’s impossible to tell whether the extra height was the natural result of a bigger flood or whether the levee and new development were partially responsible for pushing the water higher.

A Geological Survey spokeswoman said the agency could improve the Valley Park gauge to collect flow rates, but it would require extra measurements and calculations with “a much higher cost.”

There’s also been some debate about whether the levee was built too high, which would contribute to additional flooding. Six months after the Criss paper, a separate report found that the levee must have been higher than its authorized height, because at the 100-year-flood level, it would have been submerged in 2015, 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.

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