Innovative Approach to Flood Mapping Supports Emergency Management, Water Officials

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.

Working with Kansas officials as historic rainfalls of 2019 threatened several areas of Kansas with flooding, mapping efforts were focused on three critical locations.

“We modeled the Neosho River south of John Redmond Reservoir in Coffey County down to Oklahoma, which is about a 100-mile stretch,” Kastens said. “We also modeled the Neosho and the Cottonwood rivers above John Redmond, centered around Emporia close to where those two rivers come together in Lyon County. The third area was around Salina, where flooding along the Saline River and Mulberry Creek was approaching historic levels.”

When John Redmond Reservoir just above Burlington on the Neosho River was nearly at capacity and the Army Corps of Engineers was planning the release of large volumes of water, Kastens’ efforts helped inform local leaders of the potential flooding extent — and they shared his flood maps with the public.

“Using projected discharge and stage information from the Corps, we modeled Neosho River flooding at Burlington and down through the rest of Coffey County,” Kastens said. “John Redmond was built by the Corps in the early 1960s to provide flood control along the Neosho, but the reservoir flood pool had reached capacity and needed to have some pressure released to avoid compromising the dam. With the Neosho already running high, city managers and commissioners had a lot of concern with how bad it was going to get because the Army Corps was going to have start releasing a very large quantity of water out of the reservoir. I made some maps using Corps projections supplied by the Kansas Water Office and also by the Coffey County GIS coordinator, Cara Mays. It helped greatly that Cara recently completed her master’s thesis at KU using the FLDPLN model to simulate the historic 1951 flood in Burlington, so she was well aware of its capabilities.”

Going forward, Kastens — who did a lot of this work