Janesville32.4°

Rock River crest prediction revised

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Gazette staff
July 27, 2010
— The Rock River was still rising Monday, but it won’t rise as high as previously thought.

The National Weather Service revised its prediction Monday. Instead of peaking at nearly 11 feet at the Afton gauge south of Janesville, the river is now expected to peak at 10.1 feet at Afton.


That peak is expected to come at 7 p.m. today, according to a prediction issued Monday morning.


Flood stage at Afton is 9 feet.


A flood prediction is much like a weather forecast: It is revised as new information becomes available, said Chris Franks, meteorologist at the weather service’s Sullivan office.


Franks said computer models had predicted a higher peak, but then gauges upstream started showing smaller rises than predicted.


Much of the variability comes from the actions of plants, especially in a watershed as big as that of the Rock River, Franks said.


“Vegetation plays as huge role as to how much water makes it into the river, even a couple days after the rain stops,” Franks said.


The Afton gauge showed 9.82 feet at 3:15 p.m. Monday, according to information posed on the weather service’s website.


Upriver at the Indianford Dam, gauge data Monday night showed 14.57 feet. Flood stage at the dam is 15 feet. Online data do not show a prediction for the Indianford gauge.


At the Lake Koshkonong gauge near Newville, the peak was expected to come at 7 a.m. today, at 10.59 inches. Flood stage there is 10 feet.



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