Coastal dune sustainability: Understanding dune morphology, stabilization, and erosion in the face of Superstorm Sandy
Worldwide, coastal areas are some of the most densely populated localities, despite their inherent geological instability and high vulnerability to the effects of climate change. Coastal dunes offer the strongest, most natural and most cost-effective protection to buffer these localities and are therefore paramount to creating and maintaining safe, well-fortified coastlines. In 2012, Superstorm Sandy devastated the northeast United States as the most destructive hurricane of the year and most economically impactful in decades. The storm presented an opportunity to examine how New Jersey’s largest continuous natural dune system responded to a major stochastic event. At Island Beach State Park, we quantified coastal dune erosion from Superstorm Sandy as a factor of pre-Sandy beach system characteristics: dune height, beach width, and the dominant plant species stabilizing the primary dune, native Ammophila breviligulata or invasive Carex kobomugi. We assessed erosion using a combination of GIS analyses of pre- and post-Sandy aerial images in conjunction with GPS mapping of vegetation distributions. We statistically analyzed our data in a multilevel nested model.
Dune loss from Superstorm Sandy varied based on the dominant plant species fronting the dune: native Ammophila breviligulata or invasive Carex kobomugi. Dunes fronted by C. kobomugi were better stabilized and thereby suffered less erosion from Sandy. Primary dune areas fronted by C. kobomugi were also taller pre-Sandy than those stabilized by A. breviligulata. There were differences in the beach widths between the dunes occupied by the different species and the water, and this may account for some differences in dune morphology. However, beach width was not a confounding factor in our analyses examining how erosion differed with the two species. Although C. kobomugi is known to reduce native diversity and abundance, the species may be beneficial for coastal protection. These findings are contrary to past anecdotal notions that dunes stabilized by C. kobomugi were more prone to breaching. Dunes are and will continue to be our most economical and most natural form of coastal defense. This study highlights factors that contribute to quantifying and improving dune sustainability. Lessons learned here from Superstorm Sandy have important applied implications for future coastal management decisions. Understanding the geomorphological factors affecting dune sustainability is imperative to maintaining coastal homes, habitats, and recreation areas.