Tracking sediment tracer in an Eulerian model

A field survey program was designed and a numerical hydrodynamic, wave, and sediment transport model was developed to investigate transport of dredged material placed in the nearshore area of an ocean dredged material disposal site (ODMDS) adjacent to the Coos Bay inlet, Oregon. The study focuses on the understanding of coastal hydrodynamic, wave, and sediment transport processes by deploying sediment tracer and simulating the release, movement, and pathways of the tracer under combined influence of wave, current, and wind conditions within and around the immediate vicinity of the inlet.

The measured data and the model results elucidate the magnitude and spatial patterns of ebb and flood currents and capture the tidal flushing of the estuarine system. The sediment mapping feature in the numerical model performs sediment tracer tracking and helps identify sediment transport pathways that corresponds to the specific wave, hydrodynamic, atmospheric, and environmental forcing conditions during the selected simulation period. Sediment tracer tracking by data sampling and model simulation indicates that the released sediment tracer in open ocean area moves towards the inlet entrance at the initial stage of the release. Although a small portion is settled down at the inlet navigation channel, most tracer becomes entrained in the tidal flow, is carried offshore by strong ebb currents, and deposited seaward of the navigation channel. Temporal variations of sediment tracer distributions show that wave and storm conditions drive tracer transport in the open coastal area, whereas sediment pathways are primarily controlled by tidal current inside the Coos Bay and at the inlet entrance. This sediment tracer transport around the inlet system was validated by distal samples collected along the mid-reach of ODMDS.