Eastern Iowa NASA project may sharpen flood predictions

Research hopes to gain more accurate measures of rainfall and satellite imagery


Editor’s note: One in a series of stories on flood protection, a topic that The Gazette considers a content priority for 2013.

The National Aeronautic and Space Administration plans to collect Iowa precipitation data this spring that could launch a new era of timely and accurate flood predictions.

The data will help scientists understand how satellite radar images relate to actual rainfall so they can more accurately predict rainfall amounts and flood events, said Vitold Krajewski, director of the Iowa Flood Center, which is partnering with NASA on the Iowa Flood Study project.

Asked if the research would lead to more accurate forecasts that could reduce the shock experienced by Cedar Rapids residents on June 13, 2008, when the Cedar River crested more than 6 feet higher than predicted, Krajewski replied: “Yes. Eventually.”

“This experiment will yield high-quality data that will also enable us to develop mathematical models of how water flows in the environment — data that could help the flood center design specific land-use practices that could reduce the height of future floods,” Krajewski said.

The instruments deployed in Eastern Iowa will provide accurate, high-resolution measurements of rainfall that will help calibrate satellite-based rainfall estimates, said Walt Petersen, an atmospheric scientist at the NASA facility in Wallops Island, Va.

“The main objective is to determine how well our satellite radar estimates precipitation amounts. The end game, on a global basis, is more accurate and timely prediction of floods,” Petersen said.

Using the highly accurate Iowa data, “we will test ourselves, eliminate uncertainties, fine-tune our methods, figure out what little parts of our algorithms may be off,” he said.

Eastern Iowa research

NASA, better known for its work in space, will be working on the ground with the Iowa Flood Center in three Eastern Iowa watersheds: The Cedar in Linn, Benton, Black Hawk, Grundy and Tama counties; the Iowa in Grundy, Marshall, Tama and Iowa counties; and the Turkey throughout its watershed.

NASA also will collaborate with the USDA Agricultural Research Service in the operation of 22 instrument sites along the South Fork of the Iowa River in Hamilton and Hardin counties.

The Cedar, Iowa and Turkey were among nine Iowa rivers that reached record crests in June 2008 and contributed to multibillion-dollar damages.

The instruments — including portable micro rain radars, rain gauges with soil moisture probes and units that measure the size, shape, speed and number of raindrops — will be deployed this month, with data collection slated for mid-April through mid-June.

Petersen said Iowa was selected as the initial site for the advanced research because of the presence of the Iowa Flood Center, the specific expertise of Krajewski and the relative flatness of its landscape.

New equipment

Sara Steussy, a research support coordinator at the flood center, said most of the instruments will be deployed in a line running roughly from Waterloo to Iowa City, with the most powerful portable radar unit situated southwest of Waterloo.

That radar unit will fill a gap in coverage of the four National Weather Service radars operating in Iowa, Petersen said.

A second cluster of about 20 rain gauges with soil moisture sensors and two smaller portable radars will be deployed in the Turkey River valley, Steussy said.

Petersen said most of the rain gauges will be deployed in pairs to maximize the accuracy of their readings. The gauges will form a dense network that will capture the geographic variability of rainfall, he said.

Satellite radar technology will undergo a major upgrade next year with the launch of a Global Precipitation Measurement Mission satellite that, in effect, will be a “flying physics lab,” Peterson said.

It will contain two radar units operating on different frequencies as well as a radiometer that will extract information about the physical properties of precipitation, he said.The Iowa Flood Study “reflects the enormous strides scientists are making in their ability to understand and predict weather-related events,” said state Sen. Rob Hogg, D-Cedar Rapids, a longtime advocate of measures to reduce the impact of future flooding in the state.

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