Thursday, March 6, 1997
Why falling rain doesn't
always equal rising river

The Cincinnati Enquirer

Even with a half-inch to an inch of rain, the Ohio River is expected to keep falling after cresting Wednesday at 64.7 feet, forecasters say.

That forecast may sound contradictory, but it's not, said Len Mazarowski, a hydrologist with the Ohio River Forecast Center in Wilmington, Ohio.

''Flash floods in small streams and flood levels on the Ohio River are two completely different animals,'' Mr. Mazarowski said.

What the rain does is complicate predictions for how long it will take for the Ohio to return to its banks.

At Cincinnati, the river will remain above 63 feet - 11 feet above flood stage - at least until Saturday morning, the forecasting center said. It could drop below the 52-foot flood level Wednesday at the earliest.

''All of that could be delayed if we get enough rain (Wednesday night),'' Mr. Mazarowski said.

More rain might mean an extra day or two before flood refugees can start sweeping muck from their homes - and a risk for flash flooding along smaller streams.

Flash floods are caused when a strong downpour, say 2 or 3 inches, falls on a small area in a short period. The runoff rapidly fills small streams and creeks, which can overflow in a matter of hours.

But the Ohio River is so big that a few flash floods along its tributaries won't make a dent in the river level, Mr. Mazarowski said.

What really caused the Ohio River to flood was repeated rainfall over several weeks over large regions of the river basin, capped off by the massive storm that hit Kentucky and parts of southern Ohio last week.

At its peak Wednesday, the Ohio River at Cincinnati was pushing 690,000 cubic feet of water per second. To give a sense of scale, the Licking River that swamped Falmouth was moving at about 100,000 cubic feet per second at its peak Tuesday. It has been falling ever since.

The good news for Cincinnati was that the worst of the rainfall - more than a foot in some places - fell in Kentucky downstream from the city.

Had the huge downpours waited a few hours to fall farther upstream, then the worst flood in 30 years may have been the second-worst flood ever in Greater Cincinnati - with river levels well above 70 feet, Mr. Mazarowski said.