Five Minutes with: a USGS Hydrologist

Early Tuesday more than 5 1/2 inches of rainfall soaked Fairlawn in about two hours, a rare, severe weather event which caused heavy flooding and water damage.

Fairlawn-Bath Patch Editor Kymberli Hagelberg asked Greg Koltun, a hydrologist with the United States Geological Survey, to talk about the effects of the storm.

Fairlawn-Bath Patch: The National Weather Service rainfall chart shows our area received between 5 and 6 inches of rain. How does that rank?

USGS Greg Koltun: If you look at historical recurrences, a 1,000-year recurrence is 4.99 inches in two hours. 

Patch: Are we safe for a thousand years? 

USGS: No. People ask the same thing when we have two 100-year floods in five years. It means that there is a 1/1000 chance of another storm being this level or greater.  It's a rare, rare event, but that doesn't mean you couldn't have another storm like this next year -- it's just the likelihood is very small.

One-thousand year rains and floods don't always go together, either. It depends on how much rain there has been before, whether the creeks are full already and whether the ground is dry or wet.

Patch: People have been telling me all day that this happened because of global warming. What do your studies say?

USGS: You really can't say it is or isn't the cause. There seems to be evidence that global warming is occurring, but there also have always been cyclical periods of rainfall.

Patch: What happens to the water quality when these rare storms happen?

USGS: With a lot of rain you may get contaminants from the ground washing into streams and creeks, and you'll get more sediment, which is a contaminant, but what you get is usually diluted because there's so much water.

Patch: How long does it take wildlife and plants to recover?

USGS: In a creek like Schocalog, the recovery comes pretty quickly, but changes to the channel that might be caused by erosion will take longer to see. 

Patch: How many rainfall gauges do you monitor in our area?

USGS: We operate about 200 in Ohio, the closest one to you is on Schocalog Run in Copley and North Fork and Yellow Creek. To determine flood stage recurrences, we look at a minimum of 10 years of figures.

A link to rainfall gauges run by the USGS in Summit County can be found here.