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Surge overcame Cattaraugus Creek in minutes

August 30, 2009
Observer Today

Editor's note: This story is being republished from our Aug. 16 edition.

By TIM LATSHAW

OBSERVER Assistant News Editor

Article Photos

by John Carney, a number of donations for schools and residents are available at the AMVETS post in Silver Creek.

There are some height records the region can freely celebrate. Jennifer Stuczynski's pole vault of 16.14 feet is one that quickly comes to mind.

Other records, however, many wish had never happened. On Monday, Aug. 10, the height of Cattaraugus Creek reached 13.47 feet at the National Weather Service's Gowanda recording site. It was the fourth-highest crest ever officially recorded in the history of the creek and the highest in 30 years, contributing to one of the worst disasters the village has ever faced.

The weather behind the recent flooding events that hit Gowanda, Silver Creek and other areas is extremely rare, according to Mike Pukajlo of the National Weather Service (NWS) Buffalo Station. It was a matter of the wrong conditions coming together at the wrong time.

"It was a combination of upper atmospheric conditions along with the fact that the lower atmosphere was 'ripe and juicy' (for thunderstorm development) - high temperatures, sunshine, lots of humidity, high dew points and things like that. Along with prime upper air conditions, proper wind fields, moisture fields, everything just fell in line, and when that does, you'll have these kinds of events."

Storms came in two widespread lines Pukajlo said may have been part of a derecho. Literally Spanish for "straight," a derecho is a sustained windstorm that travels in a straight direction, often carrying with it thunderstorms similar to a squall line.

"We had a couple rounds of, if not actual derechos, very similar conditions with these thunderstorms," Pukajlo said. "One batch came through; they had intense rainfall with them. That first batch came through, got things going, and then the second batch came through with equal or greater rainfall amounts than the first.

"Since creeks and streams were already running pretty much at bank-full due to the first round of activity, it just couldn't hold any more."

Cattaraugus Creek's flood stage is set at 10 feet, with a moderate flooding situation said to occur at 12 feet and a major flooding classification at 14 feet. A level of 8 feet is considered an "alert stage" at which local authorities are recommended to begin flood control projects. According to NWS data, however, the "alert stage" came and passed much too quickly before flooding began.

At 7:30 p.m. on Sunday, Aug. 9, before the first round of heavy rains, Cattaraugus Creek was recorded at a height of 2 feet. The water level mildly fluctuated, but overall rose at a steady pace throughout the night, reaching 6.36 feet eight hours later at 3:30 a.m. on the morning of Aug. 10.

It was between that time and 3:35 a.m. that the water level jumped more than five feet to 11.45 feet, the apparent result of a flash flood brought on by the second round of rainfall. The flow of the creek within that time period went from 6,830 cubic feet per second to 25,200 cubic feet per second. Within the span of five minutes, NWS data suggests, Cattaraugus Creek went from a level more than 1.5 feet below the warning stage to substantial flooding.

The height and flow of Cattaraugus Creek continued to intensify following the surge of water, reaching the maximum recorded height of 13.47 inches at 11:30 a.m. Flow at that time was also at the recorded maximum of 35,400 cubic feet per second for the event. The creek level did not consistently fall below the flood stage of 10 feet until 4:30 p.m. Monday, about 13 hours after flooding first occurred.

At a public meeting Aug. 14, Gowanda Fire Chief Steve Raiport said he was with a volunteer team on Aldrich Street addressing problems caused by the downpours shortly before floodwaters began to overtake the village.

"It was just our guys, going from street to street, trying to notify residents, trying to get people out of there, dodging trees - fallen trees - cars went down the road," Raiport said. "I had white shorts that night; they turned brown. I was right there. It was just a very, very scary feeling and I never, ever hope I go through something like that again and I hope none of our residents go through it."

According to Pukajlo, the NWS predicted the potential for flash flooding in the region.

"We did have flash flood warnings out prior to the onset of actual flooding," he said. "It was anticipated, but I don't think anybody anticipated the scope of it. We were sort of ahead of the curve as far as the potential for flooding is concerned; we did have the warnings out. It's one of those things where we can't control anything once the warning's been posted."

Pukajlo did not have access to rainfall data at the time of interview, but estimated that each round of rainfall could have easily dumped up to two inches of precipitation in any given area, an amount he said would be difficult for any kind of hydrological basin to contain. At the public meeting, Cattaraugus County Director of Emergency Services Chris Baker said sources told him the overall amount was around seven inches.

"In 30 years, meteorologists haven't seen this amount of rain," Baker said. "Seven inches in two hours. If you convert that over into snow, that's 70 inches worth of snow in two hours."

As water from Cattaraugus Creek and its tributaries, Thatcher Brook and Grannis Brook, swept down streets and into Gowanda residences and businesses, Code Enforcement Officer Gary Brekcer said what the water carried with it likely added to the devastation caused.

"The U.S. Geological Surveyors have been down here and they tell us that the reason there's been so much damage with the water is because the sediment in the water is so high, it makes the water weigh more and gives it more impact when it hits things," Brecker said. "People's individual sewage disposal systems are torn up. I've seen septic tanks exhumed."

The highest level recorded by the NWS at Cattaraugus Creek in Gowanda was 14.14 feet on March 7, 1956. The most recent recorded level higher than that recorded on Aug. 10 was 13.99 feet on Sept. 14, 1979.

 
 

 

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