ADAPTATION PATHWAY FOR A BARRIER ISLAND TO FUTURE HURRICANES

Stephanie Smallegan,Evan Mazur

doi:10.9753/icce.v36.papers.52

Abstract

The numerical model XBeach is used to simulate hydrodynamics and morphological change of Bay Head, NJ, which is located on a developed barrier island. Bay Head is fronted with a seawall buried beneath its dunes, and the seawall has been shown to mitigate damage due to storm surge and waves during Hurricane Sandy (2012). The objective of this study is to re-evaluate the effectiveness of the seawall in mitigating damage from a synthetic storm and sea level rise, and refine an adaptation pathway previously created for Bay Head. Utilizing the wave and surge data generated from the North Atlantic Coast Comprehensive Study, synthetic Storm 391 is simulated using XBeach. Model results show the seawall is overtopped by storm surge and waves, causing overwash and reducing dune heights. As sea levels rise, the backbarrier region of the barrier island is severely eroded and the seawall acts as a barrier preventing elevated bay water levels from freely flowing across the island and into the ocean, exacerbating sediment transport on the backbarrier. To fully evaluate the capabilities and limitations of the seawall in mitigating storm damage, additional synthetic storms need to be simulated and the results re-evaluated. This will, in turn, lead to a comprehensive, more robust adaptation pathway for Bay Head.

Highlights

6.5% of the world’s coastlines comprise barrier islands, totaling over 15,000 km in length (Stutz and Pilkey, 2001)
The purpose of this study is to evaluate the impacts of hurricanes and sea level rise on a developed barrier island using a morphodynamic numerical model
The analysis presented in Smallegan et al (2017) is further developed by simulating a synthetic storm in addition to Hurricane Sandy under future sea levels and re-evaluating the effectiveness of adaptation strategies, its buried seawall, in mitigating damage to the New Jersey barrier island during future storms

Summary

Introduction

6.5% of the world’s coastlines comprise barrier islands, totaling over 15,000 km in length (Stutz and Pilkey, 2001). These often narrow, low-lying landforms are exposed to wave and tidal action and are sensitive to changes in sea levels. During periods of high-energy seas and elevated water levels, such as during hurricanes, barrier islands can experience extreme morphological changes (Figure 1). These processes can be described using the four storm impact regimes as described by Sallenger (2000): the swash, collision, overwash and inundation regimes. Overwash (the onshore transport of sand from the dunes and beach) and inundation (completely submerged island; often a channel or inlet is created through the barrier island) are typically most destructive

Objectives

Results

Conclusion