Understanding flood risk in White County: The result of land use and weather changes

Jesse J. Griffith

At the end of July, I had the privilege of presenting my research to Sparta Rotary Club on flood risk in White County and the Calfkiller Watershed. This presentation was based on my master’s thesis, “The Impact of Extreme Weather Patterns on Flood Risk and Mitigation in Rural Communities: A Case Study of the Calfkiller Watershed.” I am proud to share that I recently received my master’s degree from Tennessee Tech University for this work, which has focused on how land use change and weather patterns are shaping flood risk in our county.

White County has a long history of damaging floods. The Calfkiller River is notorious for flooding and has been increasing in frequency and magnitude over the past few years. More recently, in March 2021, the Calfkiller River reached over 20 feet, one of the highest crests ever recorded, causing major disruptions throughout the area. But these intense flooding events go back nearly 100 years to the 1920’s.

At the same time, White County’s landscape has been changing. Since 66% of White County is considered farmland, the Sparta community relies heavily on agriculture and farm production for our local economy. According to the USDA Census of Agriculture, White County has experienced an 18.7% decrease in total farming acres in 15 years. That means that our main source of revenue for the county is drastically decreasing.

In addition, new home construction has exploded in White County, with over 740 new homes being built since January 2020. As White County continues to grow and more farmland is replaced with roads, homes, and parking lots, the land loses some of its natural ability to absorb rainfall. Instead of soaking into the ground, more water runs off the surface, which increases flooding and puts added strain on infrastructure.

Combined with our county’s karst geology (i.e. soft limestone that creates sinkholes) and steep topography, this faster runoff increases the risk of flash flooding in both rural and urban areas. Without thoughtful planning and targeted investment in flood protection, this combination of expanding development and rural vulnerability will make future flood events even more damaging—especially as more intense storms come to our region.

For my thesis, I used Geographic Information System or GIS mapping and FEMA’s “HAZUS” disaster estimation software to simulate and model three flood scenarios across the county’s watershed: 0.5 feet, 1 foot, and 1.5 feet of flood water. Even at the lowest flood level, damages in White County could total nearly $46 million. This amount includes damage costs to housing, commercial, and government buildings, housing relocation, wage loss, and debris clean up. At 1.5 feet, that number could soar past $88 million. Critical infrastructure—including White County High School, multiple fire stations, and the Sparta Police Department—falls within these flood-prone zones.

One of the most important findings of my research is that FEMA’s current flood maps only cover the city limits of Sparta. This leaves out much of the Calfkiller Watershed, including rural communities like Doyle, Bon Air, and Cherry Creek. My analysis shows that these communities are still highly vulnerable, but they do not appear on FEMA’s maps. That means residents may not be aware of the risks or may struggle to qualify for flood insurance or mitigation assistance. FEMA’s maps focus mainly on the river channel itself, but my work looks at the whole watershed, including low-lying depressions and areas prone to runoff away from the river. This gives us a more complete picture of where water is likely to collect during a storm—and helps explain why certain neighborhoods or farms flood even when they aren’t next to the Calfkiller.

In sharing this with the Rotary Club, my message was simple: flooding may be a natural hazard, but disasters don’t have to be inevitable. Harnessing the power of GIS and flood risk mapping within our community planning can better inform emergency response teams and potentially save lives. It can also inform our farmers and local producers on low lying areas that are prone to stormwater pooling, which can influence where crops should and shouldn’t be planted. By updating our flood maps, planning more carefully where we build, and considering infrastructure solutions like restoring floodplains, zoning changes, and using permeable surfaces in new developments, we can reduce the risks to homes, farms, and businesses. With better information, we can also apply for state and federal funds to strengthen our community’s resilience. My hope is that this research sparks conversations about how to prepare for the next flood—before it arrives.