We will evaluate whether naturally vegetated dunes are more resilient to storm surge and erosion than bare or planted human-made dunes. The gradual development of natural dunes over a long period typically leads to a complex structure, due to the combination of wave, wind, and ecological processes, such as root growth. The research team will explore the trade-offs between natural and human-made dunes.
Why We Care
Sand dunes are the first line of defense from flooding, and commonly protect coastal communities from waves and storm surge. Natural dunes develop slowly and have an internal stabilizing structure consisting of roots and fungi. This may enhance the overall strength of the dune, thereby reducing erosion from storms. However, not all sand dunes form naturally; they are increasingly being constructed artificially to enhance coastal protection and resilience.
Such constructed dunes generally lack vegetation, or have vegetation planted on top following construction. As a result, constructed dunes lack the organic “skeleton” of a natural dune, potentially leaving them less stable and more vulnerable to the impacts of storms and longer-term coastal changes. However, these same human-made dunes also allow for more active sediment transport, which can buffer wave impacts by reducing water levels during storm events and may recover faster after storms, creating conditions for constructed dunes to provide additional protective services over their natural counterparts.
What We Are Doing
We will explore the trade-offs between constructed and natural dunes across the outer banks of North Carolina to inform coastal management decisions. Our work will include collection and analysis of high-resolution mobile terrestrial lidar data sets to explore dune location, shape, and changes over time. The internal geological and biological makeup of the dune will be sampled through sediment coring and in-situ monitoring with a minirhizotron camera that facilitates internal dune observations to complement the remote sensing data. Rooting structure and mycorrhizal fungi will be identified within cores. The field observations will be integrated into numerical models aimed at quantifying the role of internal biomass in reducing impacts during storms and determining how that biomass alters the style and rate of scarping. The models that result from this work will allow for the exploration of specific applied research and coastal management questions related to dune management.
Benefits of Our Work
Improving our understanding of the response of natural and artificially built sand dunes to storms and sea level rise will allow coastal managers to more effectively assess alternative management strategies. This study will communicate findings on the trade-offs between using natural dune dynamics (e.g., possibly promoting internal stability through increased biomass from root growth) and constructing or nourishing dunes (e.g., having more sand, but less internal biomass). These trade-offs have a direct application to dune management decisions made by the project’s coastal management partners.
The project is led by the Coastal Geology Lab of the Virginia Institute of Marine Science, and is funded through the NCCOS Ecological Effects of Sea Level Rise Program. Project partners include the U.S. Army Corps of Engineers Engineer Research and Development Center–Field Research Facility, and Virginia Commonwealth University's Coastal Plant Ecology Lab.