Proceedings of the 2019 Mississippi Water Resources Conference

Year: 2019 Authors: Osorio R.J., Linhoss A., Dash P.

Coastal Louisiana is facing wetland loss and land cover change. Their marshes are drowning due to land subsidence and sea-level rise. Marsh terraces are one of the many techniques that can be applied for wetland restoration by reducing wave energy in the northern Gulf of Mexico. Marsh terraces are segmented ridges of soil that are built in inland, shallow coastal ponds. They are designed to increase marsh area, dissipate wind driven waves, and encourage marsh expansion. Marsh terraces have been implemented for almost 30 years; however little research has been conducted to determine their effectiveness.

The objective of this study was to assess the change in marsh terrace area over time through remote sensing and change detection analysis. This analysis was conducted using 1-meter resolution imagery from the National Agriculture Imagery program (NAIP) from 2003 until 2017 from five Louisiana coastal Parishes. Marsh terrace sites of at least 10-14 years old were selected randomly within each Parish. Results show more cumulative deposition than erosion in marsh terraces. These results also show that terraces, which have adjacent channels, and thereby an external supply of sediment, show more deposition compared to terraces within enclosed lakes. In the future, the results obtained from this study will be also related with terrace design and environmental factors to understand which features influence marsh terraces erosion or deposition, determine trends in marsh terrace performance and possibly understand which design is most effective when accomplishing their restoration goal.