A panel of ISU faculty discussed the contributing factors to the August flooding in Ames and the risks of similar events in the future.

The presentation, “Flooding in Ames: Problems and Prospects,” was mediated by Peter Orazem, city councilman. Each of the four panelists was allowed seven minutes to present his or her ideas regarding the flood.

William Gutowski, professor of synoptic meteorology and global climate change, talked about extreme precipitation caused by changes in humidity. He said that in recent studies Des Moines showed a 13 percent increase of moisture in the atmosphere.

“Humidity levels have been going up substantially,” Gutowski said.

Increased water in the atmosphere results in heavier rainfall, he said. This scenario was apparent in the August flood, in which a three-day rainfall caused the South Skunk River to rise more than 18 feet.

Gutowski said that besides the increase in moisture in the atmosphere, a warmer planet causes more energy for storms. The combination of these factors contributes to an increase in extreme weather.

“The amount of moisture that falls out of the sky is going to increase,” Gutowski said.

Kristie Franz, assistant professor of geological and atmospheric sciences, compared the Skunk River flood levels from the past 48 years and spoke of the statistical concept of a “100-year flood.”

“The 100-year flood is a flood that has a likelihood of occurring once every 100 years,” Franz said. The chance of this happening in any given year is 1 percent, while the chance of a 500-year flood occurring is 0.2 percent.

Using the historical records of a river, she is able to see the yearly peak flows — measured in cubic feet per second — and categorize them into three groups: flows that happen frequently, that happen sometimes or that happen rarely.

Iowa had a 100-year flood in 1996 and 2008 and a 500-year flood in 1993 and 2010.

Franz said the odds of two major floods occurring within a 20-year period are .07 percent.

Franz said this .07 percent is significantly higher than the odds of winning the Iowa Power Ball lottery.

She said people still buy lottery tickets and expect to win, but are surprised when a major flood occurs — even though the chances of a flood are greater.

“[The] take-home message … is that we have to expect floods to happen,” Franz said.

She said the climate and land use are changing, and the statistical estimates need to be updated. People should always be prepared for a larger-than-anticipated flood.

Bill Simpkins, professor of geological and atmospheric sciences, said Ames gets its water supply from upstream feeds, buried valleys, tributaries and the large amount of rainfall that builds on flat surfaces.

“Everything is interconnected,” Simpkins said.

Stephen Jones, extension civil engineer, spoke of flood management in terms of the risk and reliability in structure design. He defined risk as “the probability of being flooded.”

He said risk analysis can be used as a management or design tool to better evaluate, understand and communicate flood risk.

Jones said flood risks are the likelihood of experiencing floods and the chances that the flood protection measures will hold up during such events. This is combined with the consequences of any failure to protect people, property or environment.

“Only about 20 percent of people buy flood insurance in Iowa,” Jones said. “We need to educate business owners and homeowners. We cannot predict always exactly down to the decimal point what the [flood level] is going to be.”

During the August flood, 17 buildings on the ISU campus suffered flood damage, including Hilton Coliseum, Scheman Building and Lied Athletic Recreation Center. Flood-related problems also affected 42 other buildings.

“People who built these structures in the [1960s] were not thinking of climate change,” Gutowski said.

He said people need to consider the life expectancy of the buildings and realize structures that will inevitably be flooded again and again cannot last forever.

Jones described measures that can be taken for future flood management and protection, including dams, levees, reservoirs and floodwalls, as well as land-use planning and regulation, flood warning and flood-proofing.

Simpkins said the problem with implementing prevention and risk management is that there is uncertainty surrounding the issue; people are hesitant to make major decisions based on models they are unsure about.

“There are a lot of questions that need to be asked,” Simpkins said. “We have to look into what’s right for Ames.”