Semester of Graduation

Summer 2026

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

Louisiana estuaries are shaped by the interaction of freshwater inflow, tidal forcing, wind stress, and shallow bathymetry. The estuaries are highly sensitive to navigation dredging that alters hydraulic connectivity and saltwater intrusion. This thesis investigates Calcasieu Lake, a shallow estuary in southwestern Louisiana whose exchange with the Gulf of America is strongly controlled by the 15 m deep Calcasieu Ship Channel. A 30-m horizontal resolution ROMS hindcast was developed for the Calcasieu Lake domain for the 2014 to 2018 simulation period to quantify water level variability, salinity intrusion, and vertical stratification. Validation against NOAA, USGS, and CPRA observations showed strong skill for water level and temperature, with domain-averaged RMSE and correlation values of 0.092 m and 0.943 for water level, and 1.753°C and 0.957 for temperature respectively. Salinity showed lower but still useful skill for basin-scale analysis, with an average RMSE of 5.647 psu, a correlation of 0.636, and a positive bias of 2.834 psu.

The validated control run simulation shows that Calcasieu Lake is a strongly channel-controlled compound estuary. It exhibits a mean surface salinity of 15.2 psu, a mean bottom salinity of 16.4 psu, and an estuary-averaged column-maximum Brunt–Väisälä Frequency (BVF) of 54.4 cycles/h indicating moderate density stability within the estuary mask. Using the Venice System, both mean salinities fall within the mesohaline range. The basin-averaged Hansen-Rattray parameter (Φ = 0.0786) classifies the system as well mixed at the domain scale; however, the deep ship channel experiences episodic partially mixed to salt-wedge conditions during high-discharge or weak-mixing events. Sensitivity experiments for the 2015 simulation period identify river discharge as the dominant control on basin-scale salinity and stratification. Removing river inflow increases surface salinity by 112.5% and bottom salinity by 87.3%, while removing tides freshens the basin but strengthens stratification. Removing wind stress increases the Hansen-Rattray salinity parameter by 66.8%, density-normalized contrast by 78.1%, and BVF by 60.7%, confirming that wind primarily impacts vertical mixing. Direct rainfall has only a minor basin-scale effect. Finally, a CPRA-based dredging and reclamation scenario produces smaller but measurable responses, increasing surface salinity by 5.3%, bottom salinity by 5.0%, and intrusion length by up to 1.7% basin-wide, with local surface salinity anomalies exceeding 3 psu near Rabbit Island. These results provide a physics-based foundation for estuarine management, navigation planning, and restoration design in Calcasieu Lake.

Date

7-27-2026

Committee Chair

Xue, Zuo George

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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Available for download on Monday, March 01, 2027

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