265-7 Sediment Transport Dynamics in a Complex Fluviokarst System, South-Central Kentucky

Session: New Frontiers in Cave and Karst Science (Posters)

Poster Booth No.: 106

Presenting Author:

Sarah Arpin

Authors:

Arpin, Sarah M.¹, Hodelka, Bailee N.², Dortch, Jason M.³, Tobin, Benjamin W.⁴

(1) Kentucky Geological Survey, Lexington, KY, USA; Department of Earth & Environmental Sciences, University of Kentucky, Lexington, KY, USA, (2) Kentucky Geological Survey, Lexington, KY, USA; Department of Earth & Environmental Sciences, University of Kentucky, Lexington, KY, USA, (3) Kentucky Geological Survey, Lexington, KY, USA; Department of Earth & Environmental Sciences, University of Kentucky, Lexington, KY, USA, (4) National Cave and Karst Research Institute, Carlsbad, NM, USA; New Mexico Institute of Mining and Technology, Carlsbad, NM, USA,

Abstract:

Sediment, the most common pollutant in rivers and streams, also transports harmful contaminants including nutrients, pesticides, and pathogens. In fluviokarst systems, where surface water and groundwater are intricately linked, understanding sediment movement is essential for protecting aquifers. However, most studies focus only on suspended sediment and rely on models, limiting our understanding of sediment transport. This project focuses on Stillhouse Hollow, an isolated fluviokarst system in Mammoth Cave National Park. Here, karst springs form the headwaters of the basin’s two tributaries. In the eastern tributary, the current focus of this study, water flows over Big Clifty Sandstone and sinks into the underlying Girkin Limestone, reemerging at a spring upstream of the tributary confluence. By tracking sediment through this system, we aim to identify the primary factors driving suspended and bedload transport in karst terrain.

We established three monitoring sites: one at the spring outlet, one upstream in the dry surface channel, and one in a perennial reach atop the Big Clifty. Each site includes an In-Situ Aqua TROLL 600 multiparameter sonde and an Ian Benson-designed seismic impact plate. The sondes monitor stage, temperature, conductivity, and turbidity (a suspended sediment proxy), whereas the impact plates record bedload via vibrations from coarse sediments (>8 mm) moving across the streambed. Instrumentation was deployed in March 2025.

During a major flood event in April, 26.1 cm of rain fell in 96.5 hours at the Munfordville Mesonet station—more than twice the monthly average. Although one sonde and one impact plate were lost (from different sites), preliminary results show distinct site responses and confirm the viability of seismic impact plates under extreme conditions. Bedload at the surface reach responded immediately to rainfall, with sharp impact count increases. In contrast, the spring resurgence showed peak bedload after small storms but reduced response during larger events, suggesting sediment exhaustion and transport-limited behavior.

Future work will expand monitoring basin-wide and integrate turbidity, impact, reach scale, and grain size for statistical modeling. Since climate and land use changes strongly influence sediment transport dynamics, establishing baselines is critical for predicting and mitigating future sediment-driven threats to water quality, aquatic ecosystems, and flood risks in karst terrain. More broadly, these findings highlight how sediment availability and conduit storage govern threshold-driven bedload dynamics in karst systems.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9987

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