Beach nourishment in Puget Sound: status, use, and habitat impacts

Beach nourishment is the purposeful addition of sediment to a beach. In Puget Sound, beach nourishment is used for a multitude of purposes including restoration, erosion control, and as mitigation for construction impacts or lost beach processes due to shoreline armoring. Regulators expressed a desire for a synthesis of the science surrounding beach nourishment’s effectiveness, particularly for mitigation purposes. Here we review data from peer-reviewed publications and gray literature on the use and effectiveness of beach nourishment. In our review we integrate regional expert opinions in cases where data may not exist. Further, we contextualize this synthesis with an analysis of permits that use beach nourishment in Puget Sound to understand how and where the practice is used. We found that beach nourishment is often a highly effective component of beach restoration practices, particularly when associated with the removal of hard armor. Beyond its use in restoration, beach nourishment is poorly studied for other purposes. The limited data that do exist suggest that beach nourishment performs poorly in maintaining beach conditions when associated with structures like hard armor. This is because hard armor deflects wave energy that evacuates sediment from a beach quickly and most nourishment applications occur too infrequently (usually only once) and in insufficient volumes (one or more orders of magnitude too low). However, it is unclear whether more frequent nourishment or higher volumes of nourishment would adequately address issues of using beach nourishment in front of hard armor. We discuss the implications of these findings for existing local, state, and national regulations and restoration efforts.