Potential of marshes to attenuate storm surge water level in the Chesapeake Bay

Abstract

AbstractStorm surges from tropical and extratropical storms frequently impact coastal communities globally. While the potential of natural and nature‐based features for coastal defenses has gained increased attention as a viable option for coastal flood protection, the lack of in situ measurements of storm surge attenuation has delayed their widespread utilization. We present the findings of a 3‐yr water level monitoring campaign that resulted in a large collection (52 flood events) of attenuation rates from marsh transects located in two natural preserves in the U.S. mid‐Atlantic region. Results show that the overall marsh attenuated water levels, exhibiting values up to 0.02 cm/m at Eastern Shore of Virginia National Wildlife Refuge (ES) and 0.03 cm/m at Magothy Bay Natural Preserve (MGB). In general, the greatest attenuation rates were observed at the marsh edge section. The reach close to the coastline revealed an amplification of the water level followed by water level attenuation toward the backside of the marsh. However, analyses of five major storms at ES demonstrated that, within each event, the ability of the upper marsh to attenuate water level decreased with higher inundation heights. Additionally, small spatial scales of the marsh platform, geomorphological features such as channels, elevated surrounding forests and levees seem to play a major role in reducing the attenuation rates provided by the marshes. These results indicate that, while this type of marshland would provide storm surge attenuation during low inundation heights, these ecosystems would be less effective attenuating higher water depths from extreme events.