Coastal Wetlands Exposure to Storm Surge and Waves in the Albemarle-Pamlico Estuarine System during Extreme Events

Abstract

Coastal wetlands provide a series of ecosystem services, including flood risk reduction. However, the flood risk reduction from such a complex ecosystem is dependent on incoming extreme hurricane-driven hydrodynamic and wave conditions. This study develops a numerical modeling-based approach for investigating coastal wetlands exposure to storm surge and waves during hurricanes by combining maximum water depth (MWD) and significant wave height (MHs) model outputs with the National Wetland Inventory for the Albemarle-Pamlico Estuarine System. Results show that various hurricanes lead to similar bimodal and bidirectional spatiotemporal flood patterns as a function of the lagoon’s geometry and storm track, with most overland hydrodynamic extremes impacting western Pamlico Sound and the bayside-Outer Banks. Clear positive dependency between MWD and MHS were observed over most wetland classes, with significantly higher magnitudes over estuarine emergent vegetation. In contrast to MWD, sharp MHS attenuation was found as the water propagates inland, leading to high MWD but lower MHS eventually reaching palustrine woody vegetation hundreds of meters away from the coastline. Improved understanding of how storm surge dynamics move across the bays and through the different wetland types, demonstrates the importance of considering the bay-side flood impacts over the coastal vegetation. The spatially distributed MWD and MHS estimates, along with the temporal patterns identified through the use of the TMax, allow coastal managers and engineers to better understand where, when, and by how much, the estuarine APES wetlands are more likely to be exposed to high water depths and waves.