Considerations in Using Bragg Reflection for Storm Erosion Protection

It has been suggested that Bragg reflection, the combined coherent wave reflection from a few low‐lying shore‐parallel bars, might be used to protect a beach against storm‐wave attack. Numerical models are used to examine two issues relating to the feasibility of this concept: the degree of erosion protection provided by reflecting a portion of the incident wave energy, and the degree of wave reflection that can be generated by a bar field of varying geometry. The results show that a Bragg‐reflection bar field must reflect about one‐quarter of the incident wave energy to provide a significant measure of storm erosion protection. Bar fields with uniform spacing are capable of producing the required magnitude of wave reflection, but lack sufficient bandwidth. Bandwidth can be increased by staggering the spacings between bars, however, this produces a concurrent decrease in wave‐reflection magnitude. Bragg‐reflection bar fields appear capable of providing a limited measure of storm erosion protection along U.S. Gulf Coast and Atlantic Coast beaches, but their bandwidth may be too limited for use along Pacific Coast beaches.