Evaluating the Efficacy of Natural and Nature-Based Features for Coastal Protection in the Chesapeake Bay

Coastal communities along the US mid-Atlantic region have been repeatedly impacted by storm surge causing severe economic losses. Among different alternatives to prevent flooding due to storm surge, natural and nature-based features, such as coastal marshes, are gaining importance as a form of coastal protection. In an effort to quantify their actual coastal protection services, we present the findings from an extensive field-based observation collection documenting storm surge and waves propagation over marshlands in the Chesapeake Bay, including major tropical cyclones since 2015 to date. Our study sites range from lower bay areas with semi-direct contact to the ocean (Eastern Shore of Virginia Wildlife Refuge, and Magothy Bay Natural Area Preserve) in Virginia, and mid-bay areas (Deal Island, Maryland). The field measurements documented the interaction of storm surges and waves with marshes by measuring hydrodynamic conditions in the field during extreme events (waves, currents and water levels), vegetation characteristics (stem height, stem diameter, and number of stems per square meter) and topo-bathymetric surveys. The field campaigns supported the development of new theoretical insights towards the understanding of the potential of the marshes to attenuate wave energy in the Chesapeake Bay. Thus, these field-based expressions quantified the wave energy attenuation capacity of these ecosystems during severe conditions and additionally, can predict wave attenuation based on vegetation characteristics and environmental conditions. The outcome of this study provides new practical quantitative guidelines for the adoption of nature-based strategies for coastal protection. For example, we observed that hurricane-induced waves can be efficiently attenuated by these natural features in less than 150 m. Furthermore, numerical models (XBeach) simulating wave propagation within a vegetation meadow were implemented and successfully validated. This investigation will also clarify uncertainties related to the integration of saltmarshes as a coastal protection service during storm events and the seasonal vegetation effects, providing decision makers a valuable tool to support the integration of natural solutions.