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Researcher's innovative floodplain maps help official response

When Jude Kastens was developing a new floodplain mapping model more than a decade ago as part of his doctoral dissertation at the University of Kansas, he aimed to address a critical information gap that often hindered officials during major flooding events: the lack of real-time, wide-area predictions for floodwater extent and depth.

​Dependable, detailed inundation estimates are vital for emergency managers to have enough situational awareness to quickly get the right resources and information to flood-impacted communities. In 2007, severe flooding in southeastern Kansas put a spotlight on the lack of timely, reliable projections for floodwater spread.

With heavy rains this spring (May 2019 was the wettest month ever recorded in Kansas), officials at the Kansas Water Office and Kansas Division of Emergency Management worked with Kastens, now a KU associate research professor with the Kansas Applied Remote Sensing Program at the Kansas Biological Survey, to get a more precise read on where floodwaters could rise to, based on his approach to integrating data from elevation maps, stream gauges and National Weather Service river stage forecasts.

“I worked with the Kansas Water Office in May,” Kastens said. “The ground was saturated, and the reservoirs were getting full, and with a lot more rain in the forecast, major flooding across central and eastern Kansas was looking imminent. Some years ago we’d developed this inundation library largely in collaboration with the Water Office and the Kansas GIS Policy Board but had never had the chance to put it through its paces in real time. It was based on the approach that I developed for my dissertation, and we had flood libraries for the greater eastern half of Kansas, based on the gauged stream network. For instance, if you drive south of Lawrence on Highway 59, you’ll see a USGS stream gauge box by the bridge over the Wakarusa River. There are about 200 gauges in Kansas that collect real-time stream stage information, and in times of flood, the National Weather Service provides stage forecasts several days out for a lot of these. We can take these data and map estimated current or future flooding, between gauges or around one.”

Kastens’ model (called FLDPLN, or “Floodplain”) maps potential inundation as a function of stage height using basic hydrologic principles and gridded elevation data. Because the approach requires so few inputs and little supervision, it has significant advantages for real-time mapping over existing methods such as the more precise but more complicated hydrodynamic models that FEMA uses to map 100-year floodplains.

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