Measuring suspended sand transport using a pulse-coherent acoustic Doppler profiler

A simple method to derive sediment transport rates in the nearshore from Pulse-Coherent Acoustic Doppler Profilers (PC-ADP) is described. Measured sediment concentration profiles are compared with theoretically estimated concentration profiles and exhibit good agreement. Cross-shore and longshore sediment transport rates obtained during 5-6 week long deployments on the lower shoreface in 6-8 in water depth are compared with predictions from an energetics transport model. The two estimates agree to within 20% in the longshore direction while the cumulated cross-shore wave-dominated transport component is trending significantly less offshore for the measurements than for the model predictions. The measurements indicate that significant onshore sediment transport from the lower to the upper shoreface only occurs when waves are close to breaking.