INTEGRATING OBSERVATIONS AND MODELS TO UNDERSTAND SEDIMENT DYNAMICS AT MASONBORO ISLAND, NC (Invited Presentation)

Masonboro Island, part of the National Estuarine Research Reserve (NERR) System, is an undeveloped barrier island located between two regularly nourished and developed islands in southeast North Carolina. It serves as crucial habitat for several federally threatened and listed species. While it remains undeveloped, the natural sediment dynamics supporting these habitats have been affected by human activities, such as the construction of jetties at the island's northern end and occasional sand placement on the ocean beach due to dredging in nearby inlets. Given the recent focus on beneficial use of dredged material to support local stakeholders, managers of Masonboro Island need an understanding of how sediment dynamics vary spatially and temporally. This understanding is essential for making informed decisions about whether, when, and where to advocate for sand placements on the island that could mitigate the vulnerability of ocean beach habitats and ensure that sediment can naturally replenish backbarrier marshes, critical for maintaining habitats as sea levels rise.

To support strategic planning, we have collected a comprehensive dataset including wave and meteorological conditions, storm-driven water levels, beach and dune topography from ground-based surveys and drone imagery, sediment composition, and volumes of sediment transported by wind. This synoptic dataset spans five years, collected at quarterly intervals, allowing us to quantify both intra-annual and inter-annual variability. It covers three significant hurricane events (Florence, Dorian, and Isaias) and the subsequent recovery periods, revealing substantial changes in the beachface that vary greatly across different parts of the island. Additionally, we have developed and validated numerical models to simulate storm-induced erosion, sediment transport along the shore, and the island's recovery driven by wind. In this overview, we will present the dataset and models, emphasizing key findings related to storm-induced coastal changes, modeling of overwash processes, and the observed recovery and growth rates of dunes following storm events.