Long-term sediment mobilization at a sandy inner shelf site, LEO-15

Nearly 2 years of wave and current observations are used to drive a calibrated bottom boundary layer model to examine sediment transport at the Long-term Ecosystem Observatory (LEO-15) located off of the southern coast of New Jersey. The multiyear record is of sufficient resolution to categorize sediment mobilization characteristics such as storm duration, frequency of occurrence, seasonal trends, and modes of transport at this shallow water sandy site. A total of 51 sediment transport events are identified within the 2 year timeframe. Thirty-two are categorized as winter events, and wintertime sediment transport constitutes 63% of the total for the 2 year period. In nearly all cases, bed load transport dominates the suspended load. The majority of the bed load transport is onshore due to wave asymmetries that lead to higher orbital velocities during the forward half of the wave cycle. For the remainder of events a bimodal wave spectrum is suspected to reverse the orbital velocity skewness leading to offshore transport. Suspended sediment transport is primarily directed alongshore toward the southwest, consistent with current patterns during northeasters. By including bed load transport, the net sediment transport for the 2 year period is directed primarily onshore and slightly alongshore toward the southwest.