The effects of seawalls on the beach: an extended literature review

A previous review by the author of the literature on the effects of seawalls on the beach is extended to include recent work and more thorough coverage of past studies. The present review covers approximately 100 technical papers on laboratory, field, and theoretical and conceptual studies published through mid-1988 and has three objectives: (1) to collect results of well-documented studies, (2) to summarize the state of knowledge on the seawall and beach interaction, and (3) to make recommendations for further study and field monitoring programs. It is concluded that beach change near seawalls, both in magnitude and variation, is similar to that on beaches without seawalls, if a sediment supply exists. Sediment volumes eroded by storms at beaches with and without seawalls are comparable, as are post-storm recovery rates. In addition, the shape of the beach profile after construction of a seawall is similar to the preconstruction shape if a sediment supply exists, showing the same number of bars with approximately the same volumes and relative locations. The form of the erosional response to storms at seawalls is typically different, however, with foreshore erosion that occurs on beaches without seawalls manifested as more localized toe scour and end effects of flanking and impoundment at seawalls. Limited evidence indicates that the subaqueous nearshore profile on a sediment-deficient coast with seawalls does not steepen indefinitely, but approaches an equilibrium configuration compatible with the coarser-grained particles comprising the bottom sediment.