129-47 Modeling an April 2025 Flooding Event to Understand Central Kentucky Tributary Flooding

Abstract:

River flooding represents a substantial hazard in Kentucky, with multiple events occurring across the Commonwealth in the last five years. Kentucky River communities such as Beattyville experienced flooding in March 2021, and summer floods occurred in eastern Kentucky (2022) and western Kentucky (2023). In February and April 2025, statewide flooding was observed, and central Kentucky has experienced notable flash flooding twice in the summer of 2026. While high-order streams and large rivers are well studied, their tributaries are not often monitored. This study applied a modeling workflow using ArcGIS Pro and TUFLOW to replicate observed April 2025 flooding along Elk Lick Creek, a 5^th order tributary of the Kentucky River.

A default model was assembled using a digital elevation model and vegetation layer generated from 2014 statewide 5 ft lidar point cloud data. Slope angle and vegetation height thresholds were used to create a materials raster of the watershed, and the surface hydrology of each material class was characterized. Manning’s n values were assigned based on field observations, and single ring soil infiltration rates were directly measured where possible. TUFLOW’s global rainfall method was used to apply five-minute precipitation data from an on-site weather station to the study area. For comparison to the default model, two end-member models were run using no infiltration and estimated infiltration rates based on scaled relationships between material classes.

Model results indicate that soil infiltration rates can substantially impact possible downstream flood heights. The flood height predicted by the model with the highest infiltration values was nearly 6 m below the elevation of a mud line deposited during the April 2025 flood, and even in a scenario with no infiltration, the predicted flood height was ~3 m less than the observed flood. These results suggest that the observed mud deposits within the tributary were likely only possible due to substantial back flooding of the Kentucky River and offer new insights into the contribution of higher-order streams to flooding in upstream (often ungaged) watersheds.

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