Flood Projections Way Off

By Orlan Love, Reporter

INDEPENDENCE – The National Weather Service lost some credibility here this week with its exaggerated prediction of the flood crest on the Wapsipinicon River.
"I just wish they would come up with a better system," said Bill Verslius, proprietor of Bill's Pizza and Smokehouse, a popular restaurant a block west of the river.
"Missing it by 1 or 2 feet is one thing. Missing it by more than 10 feet is not helpful at all," said Verslius, who closed his restaurant Wednesday and paid his staff to build an 80-ton sand barrier around it.
Early Wednesday, after more than 5 inches of rain fell on the Wapsipinicon basin in Buchanan and parts of Linn and Jones counties, the National Weather Service issued a warning for a 24-foot crest that would have shattered the 1999 record of 22.35 feet in Independence.
"I'm taking that seriously. It's all I have to go on," Verslius said.
Shortly before midnight that same day, the Wapsipinicon crested in Independence at 13.42 feet.
"We did over-forecast it early. The crest predictions were overdone. That is true," said Maren Stoflet, a hydrologist for the weather service in the Quad Cities.
A range of possibilities rather than a specific crest prediction probably would have been more useful in alerting the public to the dangers of a difficult-to-predict flood, she said.
Stoflet said the weather service feeds rainfall and river gauge data into a computer model and supplements that with personal expertise gained from observing floods on particular river basins.
"There are some limitations in modeling high-end response events" involving record floods, she said.
This week's flood – actually a giant flash flood rather than a systemic river flood – was especially hard to predict, Stoflet said.
There is no factual basis for speculation that the weather service has subconsciously over-predicted floods after under-predicting the 2008 Cedar River flood in Cedar Rapids, Stoflet said.
"Don't get me wrong. I'm relieved it didn't get any higher. But I think we need to have a check on the way they do flood predictions," Verslius said.
So does Austin Wright, an employee of Vern's True Value Hardware, another Independence business that closed Wednesday to prepare for the flood that never happened.
"It's like the boy who cried wolf. No one is going to pay any attention the next time," Wright said.
That same thought occurred to Sally Manson, a resident of the downstream town of Quasqueton who, with her husband Jim and some helpful friends, removed everything, including appliances, from their home on a high bank overlooking the Wapsipinicon.
"I'm thankful I'm putting dry stuff back into my house," she said Friday. "But the next time they say '24 feet,' I'm not going to believe them," she said.
Downstream in Anamosa, following a NWS prediction of a record 27-foot crest, the Wapsipinicon crested at 21.36 feet early Thursday.
Though the miss was somewhat narrower in Anamosa, Brenda Leonard, Jones County's emergency management coordinator, said the weather service's Wapsipinicon predictions "were not helpful this week."
"I think they missed the mark, but I'd rather err on the side of caution," she said.
Leonard said she "was not real confident with the 27-foot crest," but officially, at least, "that's all we have to go on."
"We have good gauge coverage on the Wapsipinicon," said supervisory hydrologist Jon Nania with the U.S. Geological Survey.
The USGS maintains seven gauges on the Wapsipinicon, six of them providing real time river stage and discharge data to the weather service computer model, he said.
"We were out verifying measurements this week, and they were all correct," he said Friday.
Nania said this week's Wapsipinicon flood, with hard rain falling quickly in a concentrated area, was "a particularly challenging event to predict."
"The weather service knows what it's doing. The system is set up to be as accurate as possible. Sometimes you get these wild ones that give them a headache," he said.
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