Findlay may be able to choose from two options to reduce the impact from future floods such as the one that struck in August 2007: reducing the hazard or lessening the exposure to risk.

Cheryl Cape, academic technology specialist: faculty liaison with the TLTC, senior lecturer, natural science

Daniel May, Ph.D., vice president for academic affairs

That was the message geologist Dr. Daniel May and geophysicist Cheryl Cape gave during their Nov. 15 presentation, “Flood Forecasting, Warning and Mitigation: A Look at the August 2007 Findlay Flood.”

The flood occurred because of a confluence of factors including unprecedented heavy rainfall of more than nine inches in 24 hours; limited infiltration of such a deluge because of local soil types; and the Blanchard River’s route across ancient lake bottom and other glacial deposits.

Given that the event has been termed a “100-year flood,” some people feel comfortable that they will never see the likes of it again in their lifetimes, but May says that’s a misinterpretation.

“It simply means that the odds are 100:1 that this could happen in any given year,” he explained.

Cape gave an overview of the Blanchard watershed, which drains 770 square miles, as part of a nested set of systems that make up the Western Lake Erie Basin. Ohio receives approximately 38 inches of rainfall a year, of which 26 inches is transpired by plants back into the atmosphere; 10 inches is shed as runoff to streams, and — largely because of the clay composition of the soil — only two inches infiltrates to groundwater and slow base discharge to streams. Heavy rains during the growing season have less impact than those in fall or winter as growing plants reduce soil moisture levels and buffer storm effects.

The Blanchard River naturally has tremendous flow variations, ranging from a base rate of about 100 cubic feet per second (CFS) to flood spikes that normally reach 5,000 CFS but, in 2007, reached 10,000 CFS several times and exceeded 15,000 CFS at the flood crest. Given those volumes and little place for the water to go, the water spread out, reaching a width of a mile and a half in some parts of town on Aug. 22, with the Main Street bridge two feet under water.

How can the community address the flooding problem?

One way to reduce damage once a storm event begins is through improvements in the warning system, which the US Geological Survey and National Weather Service have tried to address by adding four new rain and streamflow gauges to the single one that existed along County Route 140 at the time of the August flood. Individuals in floodprone areas will now have more time to protect some movable property.

To reduce the hazard, one option is to build a flood control reservoir or reservoirs upstream, which would have to cover one square mile more than 60 feet deep to accommodate the nearly 1.7 billion cubic feet of water that accompanied the major flood stage over three days during the August flood. The best location would include some natural slope to help contain the waters, May noted. Such locales are hard to find given the low topography of the county.

A second possibility is to divert the water, making it flow quickly either through or around Findlay — probably not a popular option for Ottawa and other communities downstream.

Such major projects require long-term commitment and investment, and are overseen by the Army Corps of Engineers. But Findlay can also — either simultaneously or separately — pursue other options promoted by the National Flood Insurance Program (NFIP) since 1968, to lessen risk by controlling development in the most heavily affected areas and/or preventing building in them.

FEMA prepares flood insurance rate maps under NFIP guidance to both assist with flood damage when a flood occurs and to discourage development in floodplains by adding this cost to mortgages. NFIP also supports a community rating system for flood preparedness and adds requirements to “floodproof” structures by elevating them above the 100-year floodplain. One example of this would be the plan for the apartments in the proposed River Center complex, which would have only parking on the ground floor, lessening the likelihood of personal property damage.

While both teach on the UF faculty in the same field, May as a professor of geology and vice president for academic affairs and Cape as a senior lecturer in geology, the talk was their first joint professional presentation at UF. Given the interest in the issue, they plan to offer a public version of the talk in the near future.