A holistic approach to evaluating dune cores

Abstract

As population density increases in coastal counties, shoreline stabilization efforts continue to gain momentum to protect infrastructure. Although protection techniques vary from ‘soft’ to ‘hard’ engineering, this paper focuses on a ‘hybrid’ technique utilizing geotubes as artificial dune cores. Previous literature presents conflicting results on the efficacy and potential impacts of dune cores on a beach-dune system. Here we evaluate and quantify the geomorphic impacts following dune core installation and investigate their economic feasibility. This was completed by comparing five case studies: Sea Isle City, NJ; Bolivar Peninsula, TX; Grand Isle, LA; Santa Rosa Beach, FL; and Nantucket Island, MA. An economic assessment was completed to compare dune core installation costs and repairs to alternative shoreline hardening methods. LiDAR data were used to compare dune slope, beach width, and beach volume between digital transects adjacent to and in front of the dune core installations. Digital elevation models (DEMs) were generated to provide a holistic view of geomorphic change and to assess whether erosion occurred landward of the dune core. Results indicate that dune cores are an economically feasible option compared to alternative methods. Limitations include UV exposure, wave influence, and heavy winds. Morphologically, beach width was 29.1% wider in adjacent transects and dune slope was 39.1% steeper in front of the dune core. Beach volume was lower by an overall average of 23.4%. The findings from this study suggest that dune cores are a ‘hard’ or ‘grey’ protection method.