Semester of Graduation

Summer 2026

Degree

Master of Science in Civil Engineering (MSCE)

Department

Civil and Environmental Engineering

Document Type

Thesis

Abstract

This study provides a volume-controlled numerical comparison of staggered circular and chevron marsh terrace geometries under sea-level rise and vegetation establishment. Three numerical models—Delft3D-FLOW (finite difference), Delft3D-Flexible Mesh (finite volume), and Adaptive Hydraulics (finite element)—are validated against two established morphological benchmark studies: the Gaussian hump test and the trench migration experiment. Following validation, Delft3D-FLOW is selected for the marsh terrace modeling simulations.

Staggered circular terraces in an idealized domain representative of shallow Louisiana coastal wetlands (500 m × 500 m, 2 m water depth) reduced the domain-mean significant wave height by 29.1% under current conditions, with a further 0.5% increase in wave attenuation following the addition of vegetation (Spartina alterniflora). Adding vegetation also cut domain-mean total sediment transport (bed load and suspended load) by 9.3%, showing nonlinear sensitivity of sediment transport to near-bed flow speed. A 0.3 m rise in sea level decreased the wave attenuation of circular terraces to 19.1%. Two chevron terrace designs were evaluated. An existing chevron design with 0.3 m freeboard achieved 72.8% wave attenuation under current conditions but dropped to 14.2% under 0.3 m sea-level rise as its crests were fully overtopped. A new chevron design (0.5 m freeboard) achieved 70.4% attenuation under current conditions and retained 69.8% under the same SLR scenario, as 0.2 m of freeboard remained above the raised water level. Vegetation had little impact on wave attenuation across all terrace geometries. This suggests that the chevron arm geometry creates a wave shadow beyond which additional vegetation drag provides no measurable benefit.

Date

7-17-2026

Committee Chair

Kees, Christopher E.

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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Available for download on Monday, July 16, 2029

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