Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Surf-zone integrated alongshore potential flux for oil-sand balls of varying sizes weighted by probability of wave scenario occurrence

Using observed wave conditions from NOAA buoy 42040 and Mathworks MATLAB software 2012A, the hourly wave buoy observations between 04/01/2010 and 08/01/2012 were each classified as falling into 1 of 80 wave scenarios defined by wave height and direction. For each scenario, a specific time step was identified in the record which was most representative of the other observations within the same wave height and direction bins based on both wave (height, period, and direction) and wind (speed and direction) characteristics. The characteristics of these scenarios, along with the percentage of observation in the record and the chosen representative time period, may be found in wave_scenarios.txt. The probability of occurrence for each wave scenario along with its characteristics and representative time periods were saved in MATLAB .mat format.

The D-Flow and D-Waves components of the Deltares Delft3D numerical model suite (version 4.00.01) were used to estimate bottom orbital velocity, peak period, peak wave direction, and east and north components of wind and wave-driven velocity for the offshore wave conditions corresponding to each scenario's representative time period (characteristics of which may be found in the included wave_scenarios.txt file) in each grid cell in the model domain. The wave model D-Waves, based on the Simulating WAves Nearshore (SWAN) model, is a 3rd generation phase-averaged numerical wave model which conserves wave energy subject to generation, dissipation, and transformation processes and resolves spectral energy density over a range of user-specified frequencies and directions. D-Wave was used in stationary mode. D-Flow solves the shallow water Navier Stokes equations and is run in 2-D depth-averaged mode, with linkage to D-Waves allowing the generation of wave-driven currents via wave radiation stress forcing. Default values for model parameters governing horizontal viscosity, bottom roughness, and wind drag were used. Neumann boundary conditions were used along the east, west, and south model boundaries with harmonic forcing set to zero. Model bathymetry was provided by the NOAA National Geophysical Data Center Northern Gulf Coast digital elevation map, referenced to NAVD88.
Significant wave height, dominant wave period, and wave direction were prescribed as D-Wave TPAR format files every 30 grid cells along the model boundary using results from the NOAA Wavewatch III 4' multi-grid model for a representative moment in time corresponding to the offshore wave conditions of the scenario, the specific time of which may be found in the included wave_scenarios.txt file. A JONSWAP (JOint NOrth Sea WAve Project) spectral shape was assumed at these boundary points. Wind forcing was provided using the archived WavewatchIII 4' winds, extracted from the NOAA GFS wind model, for this time. The D-Wave directional space covers a full circle with a resolution was 5 degrees (72 bins). The frequency range was specified as 0.05-1 Hz with logarithmic spacing. Bottom friction calculations used the JONSWAP formulation with a uniform roughness coefficient of 0.067 m2/s3. 3rd-generation physics are activated which accounts for wind wave generation, triad wave interactions and whitecapping (via the Komen et al parameterization). Depth-induced wave breaking dissipation is included using the method of Battjes and Janssen with default values for alpha (1) and gamma (0.73). Wave model outputs of bottom orbital velocity, peak period, and peak wave direction were extracted on the wave model grid, and current model outputs of east and north current velocity component were extracted and interpolated to the wave model grid (staggered points in relation to the current model grid).
NDBC observations from station 42012 for the representative scenario time periods were used to validate the wave model results.

Identify the spatial extent of the surf zone at each alongshore location using Mathworks MATLAB software (v2012A). The shoreline is identified from the gridded bathymetry as the cross-shore grid cell of minimum water depth at each alongshore transect. In areas where lagoons separate barrier islands and the mainland coast, the shoreline is considered along the seaward side of the barrier island only. The shoreline is not continuous due to interruptions at inlets. For each alongshore transect, the surf zone is defined as the area between the shoreline and the location of maximum wave height (found in a search area extending from the shoreline to the most offshore point of modeled depth-induced wave breaking dissipation). The extent of the surf zone (as indices into the grid at each alongshore location of the cross-shore position of the shoreline and seaward edge of the surf zone) was saved for all of the scenarios into a MATLAB .mat structure.

For each scenario, estimate the spatially variant potential flux for each SRB size class, characteristics of which may be found in the included SRB_classes.txt file. Calculations are performed in Mathworks MATLAB (v2012A). Potential flux is calculated for model output values (wave orbital velocity, peak period, and direction; depth-averaged current magnitude and direction; total water level from the model and bathymetry) using the Shield's parameter following the Soulsby-van Rijn approach described in Soulsby (1997). The direction of transport is identified is either positive (to the east) or negative (to the west) from the sign of the alongshore component of velocity (output u1 from the numerical model). The Shield's parameter is identified as a "high" critical stress value, corresponding to instances when an SRB of the identified size is within a uniform bed of similarly sized SRBs. Exposure above the bed, such as may occur with a single SRB on a sand band, reduces the critical shear stress value for incipient motion. Based on field observations of gravel and sand mixtures, a "medium" critical stress value is calculated from a constant non-dimensional Shields parameter of 0.02, and a "low" critical stress value is calculated from a constant non-dimensional Shields parameter of 0.01 (Andrews, 1983; Bottacin-Busolin et al, 2008; Fenton and Abbott, 1977; Wiberg and Smith, 1987; Wilcock, 1998). Each of these three threshold values are saved in MATLAB .mat format.
The same individual who completed this processing step completed all additional processing steps.
References:
Andrews, E.D. (1983). Entrainment of gravel from naturally sorted riverbed material. Geo. Soc. Amer. Bull. (94), 1225-1231.
Bottacin-Busolin, A., Tait, S.J., Marion, A., Chegini, A., Tregnaghi, M. (2008). Probabilistic description of grain resistance from simultaneous flow field and grain motion measurements. Water Resources Res. (44), WO9419.
Fenton, J.D., Abbott, J.E. (1977). Initial movement of grains on a stream bed: the effect of relative protusion. Proc. R. Soc. Lond. A. (352), 523-537.
Soulsby, R., 1997. Dynamics of Marine Sands, a Manual for Practical Applications. Thomas Telford Publications, London.
Wibert, P.L., Smith, J.D. (1987). Calculations of the Critical Shear Stress for Motion of Uniform and Heterogenous Sediments. Water Resources Res. (23), 1471-1480.
Wilcock, P.R. (1998). Two-Fraction Model of Initial Sediment Motion in Gravel-Bed Rivers. Science (280), 410-412.

For each scenario, integrate the alongshore potential flux at each alongshore location over the cross-shore region identified as surf zone in the previous processing step for this scenario. The 2D potential flux (in m3/m/s) is multiplied times the cross-shore width of each grid cell (in m, corresponding to half the distance from each grid cell to the grid cell to the north plus half the distance from the grid cell to the grid cell to the south) to obtain the flux (in m3/s) at that grid cell. This value is then summed over all of the cross-shore locations at that alongshore location and multiplied by SRB density (2107 kg/m3) to obtain the surf-zone integrated alongshore potential flux (in kg/s) at each alongshore location. The surf-zone integrated alongshore potential flux is then smoothed with a 2-km Hanning window filter to remove small-scale structure likely associated with model noise. These values are saved in Matlab .mat format.

For each grid cell, calculate the average surf-zone integrated alongshore potential flux from the surf-zone integrated alongshore potential flux for each scenario, weighted by the percent observation of that scenario in the time period of 04/01/2010 to 08/01/2012 (see wave_scenarios.txt).

Exported the values for each alongshore point from MATLAB format into an ArcGIS shapefile using the Mathworks MATLAB Mapping Toolbox (v2012A). The shapefile is written with the "shapewrite" command. Because MATLAB does not assign a projection, the projection corresponding to the projection associated with the bathymetry used in the numerical models is added in ArcCatalog 9.3. The file was then quality checked in ArcMap to insure values were properly exported to the shapefile from MATLAB.

Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog.

Keywords section of metadata optimized by correcting variations of theme keyword thesauri and updating/adding keywords.

Added keywords section with USGS persistent identifier as theme keyword.