Sediment Transport Processes Across a Rapidly Eroding Bare Dune

A scaled bare dune profile from Mantoloking, N.J. was constructed in the large wave flume at the NSF NHERI O.H. Hinsdale Wave Research Laboratory, Corvallis, OR., United States. Waves and water levels driven by Hurricane Sandy off the coast of Mantoloking were simulated to examine morphodynamic and hydrodynamic processes across the bare dune profile during an extreme storm. Sediment transport in the water column (suspended load), and in the sheet flow layer (bedload) were investigated. Acoustic Doppler profiling velocimeters (ADPVs) were used to measure near-bed flow velocities, conductivity concentration profilers (CCPs), and near-bed suspended sediment concentrations were obtained with optical backscatter sensors (OBSs). Offshore water surface elevations were measured by wave gauges (WGs) and non-intrusive ultrasonic distance meters quantified swash depths, instantaneous bed level progression, and free wave surface elevation shoreward the inner-surf zone. The collected data can be used to estimate sediment fluxes from the seaward berm slope to the dune front and associate them with the wave characteristics and the flow shape, the turbulence induced by the wave breaking in the nearshore, and the instantaneous bed elevation changes. The contribution of two different transport modes to the total sediment transport can be examined by comparing the suspended to the sheet flow layer fluxes. This is a unique dataset consisting of data in the swash zone during near-prototype storm conditions.