Effects of Hard Stabilization on Dry Beach Width for New Jersey

Abstract

Disagreement exists over the role of seawalls and other forms of hard stabilization in degradation of recreational beaches. Potential detrimental effects of sea walls are categorized as placement loss, passive erosion and active erosion. In this study, however, the impact of hard stabilization is studied independently of the question of mechanism of beach degradation. Dry beach widths were measured for the open ocean coast of New Jersey in order to determine the relationship between hard stabilization structures and dry beach width. Beaches were classified as one of five types discriminating on the basis of: (1) shore-parallel structure such as seawalls and revetments, (2) shore-perpendicular structures such as groins and jetties, (3) shore-perpendicular groins with no sand offset on either side, and (4) no hard stabilization structures. Beaches with stabilization structures were statistically narrower than the unstructured beaches. Although most of the beaches with shore parallel structures also contained groins, they were classified as a Type I beach and had the narrowest average dry beach width of 9 m. Beaches with groins only (Type II and III) had an average width of 18 m. Unstructured beaches were significantly wider than those with hard structures, averaging 55 m in dry width. Although hard structures may have successfully protected upland property on the New Jersey shoreline, significant beach degradation has resulted from this approach to shoreline management.