Quantifying morphological changes driven by oyster reef breakwaters under different tidal and wave conditions

In recent years, the alarming trends associated with climate change, such as extreme weather events and sea level rise, have sparked an interest in shoreline protection in coastal areas, where approximately 80% of the global population is estimated to reside. Historically, to address this issue, non-living solutions (NLS), which are anthropogenic "grey" structures such as seawalls, breakwaters, or bulkheads, have been implemented. However, these solutions exacerbate erosion and degrade local ecosystems. As a result, there is a growing interest in nature-based solutions, such as oyster reefs. A wide body of research has discussed the morphological changes induced by breakwaters in wave-dominated conditions where tidal currents are often negligible. On the contrary, it is unclear how oyster reefs perform in estuarine environments, characterized by relatively small wave heights (typically the mean wave height is about 0.1 m), and significant tidal currents that play an important role in sediment resuspension and transport. Specifically, there is a need to comprehend the factors influencing sedimentation landward of an oyster reef, such as estuarine and reef geometry, along with local hydrodynamic conditions. This research project aims to fill knowledge gaps by answering this question and evaluating the effect of tidal currents, tidal variations in water level, tidal flat profile, and the geometry of oyster reefs on morphological changes along a marshy coastline protected by oyster reefs. For this analysis, a coupled Delft3D FLOW+SWAN numerical model has been used to run a set of simulations in a relatively short period, combining the various parameters mentioned earlier. This will allow the identification of configurations that will create more significant morphological changes. These configurations will be reproduced with a physical model study that will be carried out in 2025 in the large-scale Sediment Transport Facility at the Coastal Hydraulics Laboratory, Vicksburg, MS.