Suspended Sediment Concentrations Associated with a Beach Nourishment Project on the Northern Coast of New Jersey

The potential biological effects of elevated suspended sediment concentrations caused by beach nourishment activities are a commonly cited environmental concern; however, the spatial scope and magnitude of increases in total suspended sediment (TSS) levels are infrequently monitored. In this study, suspended sediment conditions were monitored for two nourishment events on the northern coast of New Jersey in 1997 and 1998. Samples were taken in the swash, surf, and nearshore zones near the discharge pipe and at reference areas both north and south of the fill sites. Sampling was also conducted after two major storms passed through the area in September 1999 (the remnants of Hurricanes Dennis and Floyd). For both nourishment events, swash zone suspended sediment concentrations were significantly higher at sites of active discharge and recently nourished stations than at unnourished stations; however, no differences in TSS concentrations were detected between nourished and unnourished stations in the surf zone and nearshore habitats during either nourishment event. Maximum bottom surf zone and nearshore TSS concentrations related to nourishment activities were 64 mg/L and 34 mg/L, respectively, compared with respective maximum bottom concentrations of 81 mg/L and 425 mg/L after storms. Background maximum bottom TSS concentrations in the surf and nearshore zones on unnourished portions of the beach were less than 20 mg/L. Elevated TSS concentrations associated with the active beach nourishment site were limited to within 400 m of the discharge pipe in the swash zone. More direct monitoring of TSS concentrations is needed to better understand the potential biological effects of beach nourishment activities.