Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Anna C. Linhoss

Committee Member

Adam Skarke

Committee Member

Padmanava Dash

Committee Member

Mohammadmehdi Armandei

Committee Member

Prem B. Parajuli

Date of Degree

8-6-2021

Original embargo terms

Complete embargo for 1 year

Document Type

Dissertation - Open Access

Major

Biological Engineering

Degree Name

Doctor of Philosophy

College

James Worth Bagley College of Engineering

Department

Department of Agricultural and Biological Engineering

Abstract

Coastal Louisiana U.S. is facing wetland loss caused mainly by geologic subsidence and sea-level rise. These losses are accelerated by human activities such as the creation of canals and waterways for gas and oil extraction. Wetland loss in coastal Louisiana has encouraged to the implementation of various wetland restoration techniques. Marsh terraces are a one restoration technique consisting of segmented berms of soil that are built in inland coastal ponds. They are designed to increase marsh area, dissipate wind driven waves, encourage marsh expansion, and possibly reduce shoreline erosion. Marsh terraces have been implemented for almost 30 years; however, little research has been conducted to determine their effectiveness at reducing wave energy. Therefore, the overall goal of this research is to find the most optimal terrace design at reducing significant wave height, and therefore wave energy. The specific objectives of this study are to 1) assess terrace performance and longevity over time, 2) simulate wave climates in marsh terrace sites and determine the effectiveness of marsh terraces for the reduction of wave energy, and 3) assess the effectiveness of different terrace designs at reducing significant wave height during low winds and cold front passages in coastal Louisiana. These objectives were accomplished through remote sensing and numerical wave modeling. This study found that there was more predominant deposition than erosion in 20 marsh terrace fields. The study also used a numerical model to simulate small, high frequency waves in two terrace sites, finding an agreement between modeled and observed data. Moreover, wave height was reduced in terrace sites compared to unterraced sites. Finally, it was found that the chevron design is the most optimal terrace design at reducing significant wave height in a variety of wind conditions. This study adds to our knowledge of marsh terrace performance. In this way, marsh terraces may be used as an effective restoration technique at reducing wave energy, not just in Louisiana, but throughout the Gulf Coast, the U.S., and other coasts worldwide that are facing wetland loss.

Sponsorship

National Academies of Sciences, Engineering and Medicine. Gulf Research Program. grant number 2000008944

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