Natural and Nature-Based Coastal Defenses: Closing the Gap on the Potential Protection from Marshes in the US East Coast

Extreme weather events have consistently impacted coastal communities around the US and recent hurricane seasons have demonstrated the reoccurring threat that these storms have on coastal communities. Natural and nature-based features for coastal resilience are increasingly gaining popularity as an ecological engineering approach to protect coastal communities against flooding, wave energy, and erosion. However, there is still a considerable gap in accurately determining how coastal communities can safely and cost-effectively rely on natural and nature-based features for local-level resilience against flooding. While wave attenuation by coastal vegetation has been well documented in laboratory and numerical studies, fewer field-based datasets area available during extreme events. Here we present the results of field campaigns in the Chesapeake Bay and in the Outer Banks. In the former, based on a five year coastal flood monitoring campaign over natural marshes we provided support to the development of new theoretical insights towards the understanding of the potential of the marshes to attenuate wave energy and analytical expressions were derived quantifying the wave energy attenuation by these ecosystems based on vegetation characteristics and hydrodynamic conditions. In the latter site, we demonstrated that the analytical expressions developed in the Chesapeake Bay can also be applied to the Outer Banks environments and the documentation of field-based monitoring of storm surge and wave interaction with coastal vegetation. This research demonstrates a further understanding of the impacts of currents and rising sea level on wave attenuation by vegetation and the impacts of topo-bathymetric features in the attenuation capacity of the vegetation in medium energy environments (i.e. Chesapeake Bay), and in higher energy environments (i.e. Outer Banks). This presentation will demonstrate the improvement of a nearshore numerical model (XBeach) in representing the physical processes of different energy environments and improving the error and accuracies of the analytical expressions that were derived quantifying the wave energy attenuation. These field observations along with the modeling efforts provide encouraging results, validating the capacity of marshes to attenuate waves.