Proceedings of the 2020 Mississippi Water Resources Conference

Year: 2020 Authors: Osorio R.J., Linhoss A., Sharke A., French J., Brasher M.

Wetland losses in the northern Gulf of Mexico are mainly due to subsidence, sea-level rise, and land erosion caused by wind driven waves. Marsh terracing is a relatively new coastal restoration technique implemented in Texas and Louisiana. Marsh terraces are segmented berms of soil that are built in inland, shallow coastal ponds. Marsh terraces are designed to create new marsh, reduce fetch and dissipate wind originated waves. Therefore, this restoration technique is hypothesized to slow down marsh platform erosion and pond expansion by reducing wave energy. 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 which terrace design (rectangular or chevron) is most effective at reducing wind driven wave energy. This analysis was conducted using the Simulating Waves Nearshore (SWAN) model. The model simulated wind waves at two terrace fields in coastal Louisiana. Simulations were based on real terrace field conditions with and without terraces. Model input parameters included bathymetry, water level, as well as wind and wave characteristics. Model validation was done using in-field measurements collected for 5 months at each study field by an acoustic anemometer (wind time series), four doppler profilers, and a wave buoy (wave data). Results help us to understand the dynamics of wave energy related to the erosive forces exerted in two different marsh terrace designs under different field environments and weather conditions. At the end of this project we expect to identify the most effective terrace design for reducing wave energy which is related to marsh erosion, leading to marsh creation within these wetlands.