An Iowa State University researcher is hoping to develop a system for issuing long-term flood forecasts.

Chris Anderson, the assistant director of Iowa State University’s Climate Science Initiative, says he’s working with “quite a few people” to try to develop tools that will help identify specific locations where there’s a flood risk and what economic damage might occur.

“Not provide people with information that’s kind of vague, like ‘There’s a 1-in-100 chance of flooding,'” Anderson says.  “But instead put it in very concrete, everyday terms, as in ‘There’ll be very likely a loss of X amount of dollars because of building damage.'”

One big clue for long-term flood forecasting may be the changing water temperatures in the Pacific Ocean. “There are certain sea-surface temperature patterns in the Pacific Ocean that favor periods of drought and periods of very wet conditions,” he says. “And we appear to be in one that favors the wetter conditions and the question that has an unknown answer at this point is: when will that pattern reverse itself?”

A second key clue will be tracking the moisture in the Gulf of Mexico that’s pulled up by storm systems to fuel the thunderstorms that march across the Midwest.  A third clue: the moisture levels in the soil. “Once the soils become wet, that tends to enhance the amount of rainfall we receive from storms,” Anderson says. 

There’s a “scientific debate” underway, according to Anderson, to figure out which of those three main factors may be most important and how the soil moisture, moisture from the Gulf of Mexico and water temperatures in the Pacific interact to produce thunderstorms in the Midwest.

Anderson is considering the impact of heavy rainfall, too.  He’s calculating, for example, how soil absorbs a two-inch rain as opposed to a four-inch rain. “To figure out, at the higher rates, what fraction of that rainfall will actually not soak into the ground because it’s accumulating too quickly,” Anderson says.

Anderson suggests with flood events occuring more frequently over the past two decades, it’s important to develop new systems for gauging the potential for flooding as the old 100-year and 500-year flood models may be outdated. 

Anderson is one of several I.S.U. researchers examining the National Centers for Environmental Prediction’s “Climate Forecast System.”  Their study is financed by the National Oceanic and Atmospheric Administration