Storm Surge and Wave Heights Impacts over Coastal Wetlands during Extreme Events: A Case-Study in the Albemarle-Pamlico Estuarine System

Coastal wetlands in the Albemarle-Pamlico Estuarine System (APES) are exposed to extreme water levels and wave height conditions during hurricanes. Although coastal wetlands are known to provide wave attenuation and flood risk reduction during smaller storms, their ability to attenuate waves and water level during major events like hurricanes is less certain. During large storms there may be a reduction in ecosystem services, in particular their ability to provide flood protection to coastal communities and infrastructure. In this study, a numerical modeling-based approach was developed for investigating coastal wetlands exposure to storm surge and waves during four major recent hurricanes. A high-resolution nearshore numerical mesh was developed and used in the two-way coupled ADCIRC+SWAN model, which was calibrated and validated for Hurricanes Irene, Matthew, Florence and Dorian. In order to assess the coastal wetland exposure, model outputs such as maximum water depth () and significant wave height () were combined with the coastal wetland vegetation from the National Wetland Inventory. Results showed that according to the estuary's geometry and the storm track, similar bimodal and bidirectional spatiotemporal flood patterns were observed in the APES, with most overland hydrodynamic conditions impacting western Pamlico Sound and varying portions of the Outer Banks. and were significantly higher over estuarine emergent vegetation when compared to other coastal wetlands, reaching of over 2 meters and of almost 1 meter. Although, did not decrease significantly as storm surge moved landward, sharp reductions in were simulated for all storms close to the marsh edges exhibiting strong wave reduction. Additionally, for both hurricanes Irene and Florence (particularly large storms with high wind speeds) high and lower propagated beyond the estuarine wetlands reaching palustrine woody vegetation hundreds of meters inland. Our findings serve as an initial evaluation of the expected hydrodynamic and waves conditions impacting coastal vegetation during extreme events, potentially supporting the implementation of coastal defenses by natural marshes management and engineering practices.