Observations and modeling of a tidal inlet dye tracer plume

Abstract

A 9 km long tracer plume was created by continuously releasing Rhodamine WT dye for 2.2 h during ebb tide within the southern edge of the main tidal channel at New River Inlet, NC on 7 May 2012, with highly obliquely incident waves and alongshore winds. Over 6 h from release, COAWST (coupled ROMS and SWAN, including wave, wind, and tidal forcing) modeled dye compares well with (aerial hyperspectral and in situ) observed dye concentration. Dye first was transported rapidly seaward along the main channel and partially advected across the ebb‐tidal shoal until reaching the offshore edge of the shoal. Dye did not eject offshore in an ebb‐tidal jet because the obliquely incident breaking waves retarded the inlet‐mouth ebb‐tidal flow and forced currents along the ebb shoal. The dye plume largely was confined to <4 m depth. Dye was then transported downcoast in the narrow (few 100 m wide) surfzone of the beach bordering the inlet at 0.3 m s−1 driven by wave breaking. Over 6 h, the dye plume is not significantly affected by buoyancy. Observed dye mass balances close indicating all released dye is accounted for. Modeled and observed dye behaviors are qualitatively similar. The model simulates well the evolution of the dye center of mass, lateral spreading, surface area, and maximum concentration, as well as regional (“inlet” and “ocean”) dye mass balances. This indicates that the model represents well the dynamics of the ebb‐tidal dye plume. Details of the dye transport pathways across the ebb shoal are modeled poorly perhaps owing to low‐resolution and smoothed model bathymetry. Wave forcing effects have a large impact on the dye transport.

An Experimental Evaluation of the Feasibility of Inferring Concentrations of a Visible Tracer Dye from Remotely Sensed Data in Turbid Rivers

“…The potential to map dispersion patterns via remote sensing was first demonstrated in coastal environments [6,7]. Clark et al [6] showed that passive optical image data could be used to estimate Rhodamine WT dye concentrations in the surf zone and identify eddies and other small-scale structures (on the order of 10 m) associated with the dispersion of a dye pulse.…”

Roles of Wind‐Driven Currents and Surface Waves in Sediment Resuspension and Transport During a Tropical Storm

“…COAWST consists of a mesoscale atmosphere model, a regional ocean model, a model for simulating surface waves, a sediment transport model, and a dynamic coupler to exchange data fields between the submodels. It has been used in a number of studies on sediment dynamics in coastal oceans, during both storm and nonstorm conditions (e.g., Feddersen et al, ; Kumar et al, ; Kumar & Feddersen, ; Olabarrieta et al, ; Sclavo et al, ).…”

“…COAWST consists of a mesoscale atmosphere model, a regional ocean model, a model for simulating surface waves, a sediment transport model, and a dynamic coupler to exchange data fields between the submodels. It has been used in a number of studies on sediment dynamics in coastal oceans, during both storm and nonstorm conditions (e.g., Feddersen et al, 2016;Kumar et al, 2015;Kumar & Feddersen, 2016;Olabarrieta et al, 2011;Sclavo et al, 2013). In our implementation of COAWST for Chesapeake Bay, we did not run the Weather and Research Forecasting model for the regional atmosphere and couple it to the ocean and wave models since wind speeds over fetch-limited Chesapeake Bay are challenging to predict.…”

X‐Band Radar Mapping of Morphological Changes at a Dynamic Coastal Inlet

“…Here we report on marine X‐band radar observations of the New River Inlet, North Carolina, utilized to observe morphological variability. The fieldwork was conducted during the Office of Naval Research (ONR) sponsored Inlets and Rivers Mouth Dynamics Departmental Research Initiative (RIVET‐I) experiment in May 2012 (e.g., Chen et al, ; Feddersen et al, ; MacMahan et al, ; Pianca et al, ; Rogowski et al, ; Spydell et al, ; Wargula et al, ; Zippel & Thomson, ). The work uses ensemble averages of continuous X‐band radar scans (42 rotations per minute) to delineate shoal positions within inlet.…”