Author ORCID Identifier

https://orcid.org/0009-0009-1948-9612

Date Available

8-15-2025

Year of Publication

2025

Document Type

Master's Thesis

Degree Name

Master of Civil Engineering (MCE)

College

Engineering

Department/School/Program

Civil Engineering

Faculty

Dr. James Fox

Faculty

Dr. Mei Chen

Abstract

This thesis investigates the autogenic sediment transport regime in a low-gradient stream system in the inner bluegrass region of central Kentucky, USA The seasonality of sediment transport seasonality was not well addressed in prior research for baseflow and low flow periods, to our knowledge, due to the assumption that low flows do not account for considerable fluid transport capacity to move sediment. The hypothesis is that during the autogenic regime the sediment transport in the low-gradient system is being driven by geophysical, biogeochemical, and biological processes. We hypothesize that crayfish are one mechanical driver of sediment transport during these periods.

The research reported in this thesis relies on water quality sensor datasets collected by the author and colleagues, and the quality assurance quality control (QAQC), sensor maintenance, and calibration processes helped ensure that the data used in this thesis is robust. Sediment signal analyses assessed the turbidity data on a daily, seasonal, yearly, and multi-year time scales to see how the baseflow sediment signal was impacted; and the author carried out data analyses including sediment duration curves, empirical mode decomposition, and a diel trend analysis. A sediment continuity model based on shear stress was created to assess the impact that crayfish and the fluid impart on sediment transport.

Results of QAQC using the GCE Toolbox showed that between 55% and 95% of the recorded data was deemed suitable, based on the parameter, including pH, dissolved oxygen, temperature, turbidity, conductivity and nitrate. Results of visualization of the seasonality of autogenic turbidity within the watershed showed that there are seasonal periods when the sediment concentration in water is higher, including the early summer months, turbidity=16 NTU; (26.9 mg/L), as compared to low periods during winter months, turbidity=3 NTU; (11.2 mg/L). The sediment duration curve analyses showed that 25% of the load is from the autogenic sediment transport in the watershed. The autogenic regime is visually correlated with temperature and not discharge, leading us to believe that there is potentially a biological control of the sediment signal during this regime. The empirical mode decomposition results show that the best aggregation of the data is the daily aggregation, and the significant IMFs correspond to a six-month time scale that show the seasonal trend for the baseflow sediment transport. The diel trend analysis shows that crayfish move more sediment during the night than during the day, including 0.6 NTU (8.2 mg/L) higher in November and 2.3 NTU (10.3 mg/L) higher in June. The crayfish account for between 8% and 44% of the autogenic sediment transport depending on the month. The shear stress model shows that crayfish are an effective driver of sediment transport, but they still account for less sediment transport than the fluid sediment transport. The crayfish account for approximately 16% of the autogenic sediment transport in 2018, as compared to 84% of sediment transport attributed to fluid shearing.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2025.428

Funding Information

This study was supported by the National Science Foundation's Inclusive mentoring hub for enabling pathways from inner-city and rural Appalachian households to engineering in Kentucky and West Virginia Grant (no. 2217685) from 2022 until present.

This study was supported by the National Science Foundation's Sensing and Educating the Nexus to Sustain Ecosystems Grant (no. 1632888) from 2016 until 2021.

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