A nourished beach is a carefully designed engineering project with many positive synergistic effects, not a simple dump of sand on the berm. Unfortunately, many projects are perceived to have failed in a storm only because the dynamics and intent of the design are not fully understood.
Coastal engineers expect that large storms will transport some sand from the beach and dune to areas offshore when they take the brunt of storm waves. When the beach profile is lowered in this fashion and the material is dragged seaward, waves start to break further out and are weakened by the time they reach the shoreline. Cutting the wave energy effectively protects the dune and upland property from further erosion and decreases the severity of flooding.
Therefore a nourished beach with a sufficient amount of sand and a healthy dune may erode during a storm, but does so in place of more costly damages further onshore. Much of the sand transported to the nearshore will eventually return to the beach with the lower energy post-storm waves. Over time, however, a series of storms may transport enough sand outside of the sand-sharing system (the project area) to reduce the protective ability of the nourished beach. At this time, the project has reached its design life and re-nourishment is recommended.
So, the next time you’re out at your favorite beach (whether it’s nourished or natural) after a storm, think about what the surrounding area would look like had there not been enough sand in place to buffer the impacts of the storm. Often after a major storm, the cost of the eroded sand is small compared to the cost that would have been required to clean up rubble and repair damaged roads, houses and buildings.