Degree

Doctor of Philosophy (PhD)

Department

Geology and Geophysics

Document Type

Dissertation

Abstract

This study explores the use of shear-wave seismic reflection and electrical resistivity techniques to complement our understanding of seepage pore pressure variations and soil type estimation beneath earthen levees in the Mississippi River floodplain. The seasonal variations of water level in the river create changes in pore pressure in the adjacent aquifer, which can be detected using time-lapse shear-wave velocity analysis. The seismic reflection patterns during these pressure variations show changes in velocity that can be translated into changes in effective pressure, allowing us to distinguish between confined and leaky aquifers.

In addition, the integration of geophysical methods such as shear-wave seismic reflection and electrical resistivity tomography is used to determine the geomorphology of fluvial sediments and their impact on the hydraulic properties of the soil. Ridges and swales play a crucial role in altering the thickness of the overlying blanket layer, affecting the quality of the low permeability layer above the aquifer.

Finally, this study utilizes statistical and machine learning techniques such as least-squares surface fitting and random forest models to estimate soil type on the landside of a flood-protection levee using electrical resistivity values and S-wave velocities. Data from a floodplain point bar setting in Louisiana is used, where swale-filling clays separating sandy ridges deposits are the main surface features comprising the upper 10 meters of highly heterogeneous sediments.

Date

4-11-2023

Committee Chair

Lorenzo, Juan

DOI

10.31390/gradschool_dissertations.6086

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Available for download on Tuesday, April 01, 2025

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