Study shows how beach and dune nourishment can mitigate the long-term impacts of storms and sea-level rise on barrier islands

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On developed barrier islands, shore protection strategies such as beach and dune nourishment are used to reduce flooding, wave impact, and erosion during storm events. The effects and/or benefits of these actions are often considered temporary, thus requiring periodic maintenance or renourishment. Given limited budgets for coastal protection, it is important to make decisions around nourishment with consideration of how sand moves once it is placed, and how it provides protection into the future to the nourishment site and surrounding region. While most studies provide insight into the potential for nourishment to mitigate the short-term (i.e., < 10 years) impacts of storms, the ability of nourishment to mitigate the long-term effects of multiple storms and sea-level rise remains unknown.

Scientists at the USGS St. Petersburg Coastal and Marine Science Center, University of Georgia, Louisiana State University, The Water Institute of the Gulf, and the U.S. Army Corps of Engineers, funded by the USGS CMHRP and NOAA NCCOS, conducted research to assess the effectiveness of beach and dune nourishment on barrier island morphological resilience over decadal time scales. The study, published in the journal Water, focused on Dauphin Island, Alabama, a low-lying barrier island that has been severely impacted by extreme storm events. Integrated high-resolution models were used to simulate barrier island evolution, accounting for fair-weather conditions, storm-driven change, and post-storm dune recovery. The cumulative effects of beach and dune nourishment were assessed over a 30-year simulation period to determine how nourishment can influence barrier island resiliency over long time scales, including the effects of sea-level rise. Results showed that during stronger storms, nourishment reduced dune overtopping, allowing the island to maintain height and width, whereas the no-action (no nourishment) scenario resulted in island rollover (moving the island landward) but decreased island height. Nourishment was particularly effective in reducing erosion and breaching during back-to-back storms occurring in the same year. The results of this study provide insight into how beach and dune nourishment can improve morphological resilience by maintaining barrier island geometry and volume over decadal timescales. Future efforts assessing the dynamic effects of sea-level rise and the ability of nourishment to improve barrier island resiliency can benefit from this work.

To read the companion story at NCCOS, visit: "Evaluating the Long-term Effect of Nourishing Dauphin Island Beaches."

Read what else is new at the St. Petersburg Coastal and Marine Science Center.