Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Ratio of wave- and current-induced shear stress to critical values for oil-sand ball and sediment mobilization

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Frequently-anticipated questions:

What does this data set describe?

Title:
Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Ratio of wave- and current-induced shear stress to critical values for oil-sand ball and sediment mobilization
Abstract:
The U.S. Geological Survey has developed a method for estimating the mobility and potential alongshore transport of heavier-than-water sand and oil agglomerates (tarballs or surface residual balls, SRBs). During the Deepwater Horizon spill, some oil that reached the surf zone of the northern Gulf of Mexico mixed with suspended sediment and sank to form sub-tidal mats. If not removed, these mats can break apart to form SRBs and subsequently re-oil the beach. A method was developed for estimating SRB mobilization and alongshore movement. A representative suite of wave conditions was identified from buoy data for April, 2010, until August, 2012, and used to drive a numerical model of the spatially-variant alongshore currents. Potential mobilization of SRBs was estimated by comparing combined wave- and current-induced shear stress from the model to critical stress values for several sized SRBs. Potential alongshore flux of SRBs was also estimated to identify regions more or less likely to have SRBs deposited under each scenario. This methodology was developed to explain SRB movement and redistribution in the alongshore, interpret observed re-oiling events, and thus inform re-oiling mitigation efforts.
Supplemental_Information:
This data layer is a subset of USGS Open-File Report 2012-1234, Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance. It is part of a set of data layers describing mobility for a range of wave climate scenarios. The specific wave conditions for this layer are indicated by the file name (of format Hh_Dd_mobile), and in attributes in the shapefile, and may be found by comparing the scenario name (Hh_Dd) to the look-up table included in the GIS zip file, wave_scenarios.txt. SRB class and sediment properties may be found in the look-up table included in the GIS zip file, SRB_casses.txt.
  1. How should this data set be cited?

    Dalyander, P. Soupy , Long, Joseph W. , Plant, Nathaniel G. , and Thompson, David, 2012, Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Ratio of wave- and current-induced shear stress to critical values for oil-sand ball and sediment mobilization: Open-File Report (OFR) 2012-1234, U.S. Geological Survey, Coastal and Marine Geology Program, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL.

    Online Links:

    This is part of the following larger work.

    Plant, Nathaniel G. , Long, Joseph W. , Dalyander, P.Soupy, and Thompson, David, 2012, Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Open-File Report (OFR) 2012-1234, U.S. Geological Survey, Coastal and Marine Geology Program, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -88.716961
    East_Bounding_Coordinate: -85.412528
    North_Bounding_Coordinate: 30.690796
    South_Bounding_Coordinate: 29.400356

  3. What does it look like?

    model_bathymetry.jpg (JPEG)
    Graphic showing the numerical model domain over which analysis is conducted.

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 01-Apr-2010
    Ending_Date: 01-Aug-2012
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: vector digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      Indirect_Spatial_Reference: Gulf of Mexico
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • G-polygon (661210)

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.01 m
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?

    Hh_Dd_mobility
    Ratio of wave- and current-induced shear stress to critical values for oil-sand ball and sediment mobilization for specific wave scenarios (Source: USGS)

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    Scenario_H
    Scenario wave height number (e.g., "h" in Hh_Dd, see wave_scenarios.txt) (Source: USGS)

    Range of values
    Minimum:1
    Maximum:5
    Units:non-dimensional
    Resolution:1

    Scenario_D
    Scenario wave direction number (e.g., "d" in Hh_Dd, see wave_scenarios.txt) (Source: USGS)

    Range of values
    Minimum:1
    Maximum:16
    Units:non-dimensional
    Resolution:1

    sediment
    Unitless ratio of the combined wave- and current-induced shear stress to the critical stress for 300 micron quartz sand calculated from the Shield's parameter. Values greater than one indicate sand is likely mobilized under the wave conditions associated with this scenario. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB1_high
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 1 (see SRB_classes.txt) calculated from the Shield's parameter. The Shield's parameter is a relatively high critical stress estimate and does not account for a reduced critical stress due to potential SRB exposure above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB1_med
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 1 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.02. This critical stress estimate is a mid-range value accounting for a reduced critical stress due to some exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB1_low
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 1 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.01. This critical stress estimate is a low value accounting for a reduced critical stress due to exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB2_high
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 2 (see SRB_classes.txt) calculated from the Shield's parameter. The Shield's parameter is a relatively high critical stress estimate and does not account for a reduced critical stress due to potential SRB exposure above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB2_med
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 2 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.02. This critical stress estimate is a mid-range value accounting for a reduced critical stress due to some exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB2_low
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 2 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.01. This critical stress estimate is a low value accounting for a reduced critical stress due to exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB3_high
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 3 (see SRB_classes.txt) calculated from the Shield's parameter. The Shield's parameter is a relatively high critical stress estimate and does not account for a reduced critical stress due to potential SRB exposure above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB3_med
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 3 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.02. This critical stress estimate is a mid-range value accounting for a reduced critical stress due to some exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB3_low
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 3 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.01. This critical stress estimate is a low value accounting for a reduced critical stress due to exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB4_high
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 4 (see SRB_classes.txt) calculated from the Shield's parameter. The Shield's parameter is a relatively high critical stress estimate and does not account for a reduced critical stress due to potential SRB exposure above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB4_med
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 4 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.02. This critical stress estimate is a mid-range value accounting for a reduced critical stress due to some exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB4_low
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 4 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.01. This critical stress estimate is a low value accounting for a reduced critical stress due to exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB5_high
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 5 (see SRB_classes.txt) calculated from the Shield's parameter. The Shield's parameter is a relatively high critical stress estimate and does not account for a reduced critical stress due to potential SRB exposure above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB5_med
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 5 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.02. This critical stress estimate is a mid-range value accounting for a reduced critical stress due to some exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB5_low
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 5 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.01. This critical stress estimate is a low value accounting for a reduced critical stress due to exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB6_high
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 6 (see SRB_classes.txt) calculated from the Shield's parameter. The Shield's parameter is a relatively high critical stress estimate and does not account for a reduced critical stress due to potential SRB exposure above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB6_med
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 6 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.02. This critical stress estimate is a mid-range value accounting for a reduced critical stress due to some exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

    SRB6_low
    Unitless ratio of the combined wave- and current-induced shear stress for this scenario to the critical stress for SRB class 6 (see SRB_classes.txt) calculated from a non-dimensional Shield's parameter of 0.01. This critical stress estimate is a low value accounting for a reduced critical stress due to exposure of the SRB above the seafloor. (Source: USGS)

    Range of values
    Minimum:0
    Maximum:100
    Units:non-dimensional
    Resolution:0.01

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    P. Soupy Dalyander
    U.S. Geological Survey
    Oceanographer
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    (508) 548-8700 x2290 (voice)
    (508) 457-2310 (FAX)
    sdalyander@usgs.gov

Why was the data set created?

This GIS layer contains an estimate of the ratio of combined wave- and current- induced shear stress in the shallow northern Gulf of Mexico (Alabama and portion of the Florida coast) for a single set of wave conditions to the critical stress of surface residual balls (SRB) of various sizes and local sediment. Values greater than one indicate the threshold for incipient motion is exceeded, and the SRB or sediment is likely mobilized. This output is based on numerical model output of wave and circulation patterns for a given wave height scenario, corresponding to a particular set of offshore wave conditions at NOAA NDBC buoy 42040. The specific wave conditions for a given shapefile are indicated by the file name (of format Hh_Dd_mobile) and may be found by comparing the scenario name (Hh_Dd) to the look-up table included in the GIS zip file, wave_scenarios.txt. Characteristics of SRB classes and the sediment properties used may be found in the look-up table included in the GIS zip file, SRB_casses.txt. This data layer is intended to show regions of likely mobilization for intended use by individuals in SRB mitigation attempting to explain redistribution or burial of SRBs under specific wave conditions.

How was the data set created?

  1. From what previous works were the data drawn?

    NOAA GFS (source 1 of 2)
    NOAA National Centers for Environmental Prediction (NCEP), 20110601, NOAA/NCEP Global Forecast System (GFS) Atmospheric Model: NOAA National Centers for Environmental Prediction, Camp Springs, MD.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Wind speed data at 10 m above the sea surface from the NOAA Global Forecast System (GFS) 0.5 degree model is interpolated by NOAA to the 4' Wavewatch3 grid and archived. These archived data are used to drive the numerical wave and circulation model that creates estimated of bottom shear stress.

    NOAA WW3 (source 2 of 2)
    NOAA National Centers for Environmental Prediction (NCEP, 20121001, NOAA/NWS/NCEP 4' Wavewatch III Operational Wave Forecast: NOAA National Centers for Environmental Prediction, Camp Springs, MD.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Boundary conditions for the wave model were provided by the 4' NOAA/NWS/NCEP Wavewatch III operational ocean wave forecast.

  2. How were the data generated, processed, and modified?

    Date: 2012 (process 1 of 4)
    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 this scenario Hh_Dd (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.

    Person who carried out this activity:

    Joseph W. Long
    U.S. Geological Survey
    Oceanographer
    600 4th Street S
    St. Petersburg, FL 33701
    USA

    (727) 803-8747 x3024 (voice)
    (727) 803-2032 (FAX)
    jwlong@usgs.gov

    Data sources used in this process:
    • NOAA GFS
    • NOAA WW3

    Data sources produced in this process:

    • DELFT3D

    Date: 2012 (process 2 of 4)
    Use the wave model and current model results to calculate the bottom shear stress within each model grid cell using Mathworks MATLAB software (v2012A). The wave-current stress was calculating following the method of Soulsby (1995) to parameterize four methods giving good overall performance for estimating wave-current stress, based on original formulations by Grant and Madsen (1979), Fredsøe (1984), Huynh-Thanh and Temperville (1991), and Davies et al. (1998). The combined wave-current stress for the individual components of wave and current stress was calculated for hydrodynamic model output following the method prescribed in Soulsby (1997) for each of the four methods. The mean value of the four methodologies was used to estimate the combined wave-current shear stress for the hydrodynamic scenario. Wave direction, bottom orbital velocity, and period, and depth-averaged current magnitude and direction, required for this calculation, are calculated internally by the model. The roughness used is 1/12 the diameter of the SRB or sediment being analyzed, following Soulsby (1997). Stress values are saved in MATLAB .mat format.

    The same individual who completed this processing step completed all additional processing steps.

    References: Davies, A.G., Soulsby, R.L., King, H.L. (1988). A numerical model of the combined wave and current bottom boundary layer. J. Geophys. Res. 93, 491-508.

    Fredsøe, J. (1984). Turbulent boundary layer in wave-current motion. J. Hydraul. Eng. ASCE (110), 1103-1120.

    Grant, W.D., Madsen, O.S. (1979). Combined wave and current interaction with a rough bottom. J. Geophys. Res. (84), 1797-1808.

    Huynh-Thanh, S., Temperville, A. (1991). A numerical model of the rough turbulent boundary layer in combined wave and current interaction, in Sand Transport in Rivers, Estuaries, and the Sea, eds. R. L. Soulsby and R. Bettess, pp 93-100. Balkema, Rotterdam.

    Soulsby, R.L. (1995). Bed shear-stresses due to combined waves and currents, in Advances in Coastal Morphodynamics, eds. M.J.F. Stive, H.J. de Vriend, J. Fredsøe, L. Hamm, R.L. Soulsby, C. Teisson and J.C. Winterwerp, pp. 4-20 and 3-23. Delft Hydraulics, Netherlands.

    Soulsby, R.L. (1997). Dynamics of Marine Sands. Thomas Telford Publications: London, 249 pp.

    Person who carried out this activity:

    P. Soupy Dalyander
    U.S. Geological Survey
    Oceanographer
    384 Woods Hole Road
    Woods Hole, MA 02540
    USA

    (508) 548-8700 x2290 (voice)
    (508) 457-2310 (FAX)
    sdalyander@usgs.gov

    Data sources used in this process:
    • DELFT3D

    Data sources produced in this process:

    • WC STRESS

    Date: 2012 (process 3 of 4)
    Estimate the critical shear stress for 300 micron quartz sediment and 6 SRB size classes and take the ratio of the combined wave-current stress to this critical value at each grid point. The specific characteristics for the sediment and SRB classes may be found in the included SRB_classes.txt file. Calculations are performed in Mathworks MATLAB (v2012A). Critical stress thresholds are calculated using the Shield's parameter following Soulsby (1997) and saved in MATLAB .mat format. In the case of SRBs, 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). Because the in-situ sediment is assumed to be of a relatively uniform size, a single critical stress value based on the Shields parameter is used.

    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.

    Data sources used in this process:

    • WC STRESS

    Data sources produced in this process:

    • RATIO

    Date: 2012 (process 4 of 4)
    Export the values for each grid cell from MATLAB format into an ArcGIS shapefile using the Mathworks MATLAB Mapping Toolbox (v2012A). Land grid cells are not exported to Arc. 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.

    Data sources used in this process:

    • RATIO

  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    The attributes in this data layer corresponds to the ratio of combined wave-current shear stress to the critical stress value for surface residual balls (SRBs) and sediment of a particular size and density (specific parameters may be found in the included SRB_classes.txt files) for the wave conditions of Hh_Dd, characteristics of which may be found in the included wave_scenarios.txt file. Statistical values will vary if a different numerical model is used for the hydrodynamics, or if a different method is used in calculating wave-current stress or critical stress.

  2. How accurate are the geographic locations?

    Numerical models are used in the generation of hydrodynamic conditions used in creating this data layer. Because the overall horizontal accuracy of the data set depends on the accuracy of the model, the underlying bathymetry, forcing values used, and so forth, the spatial accuracy of this data layer cannot be meaningfully quantified.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    This statistic was calculated at all locations (wet grid cells) where model output exists. Because of differences between the scenarios, not all grid cells may be included in all scenarios. The statistic was calculated for a particular scenario (Hh_Dd), the characteristics of which may be found in the included wave_scenarios.txt file, and for sediment and various classes of SRBs, the characteristics of which may be found in the included SRB_classes.txt file. The bottom shear stress was calculated from wave and current estimates generated with Delft3D, and would vary if different models were used or if different model inputs (such as bathymetry, forcing winds, and boundary conditions) or parameterizations were chosen. Calculated currents were depth-averaged and therefore the calculated mobility values are expected to be most valid in well-mixed regions, e.g., the surf zone. Mobility estimates would vary for different size or density objects and/or if a different formulation for calculating the critical stress value is used.

  5. How consistent are the relationships among the observations, including topology?

    No duplicate features are present. All polygons are closed, and all lines intersect where intended. No undershoots or overshoots are present.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
Use_Constraints:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.

  1. Who distributes the data set? (Distributor 1 of 1)

    P. Soupy Dalyander
    U.S. Geological Survey
    Oceanographer
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    (508) 548-8700 x2290 (voice)
    (508) 457-2310 (FAX)
    sdalyander@usgs.gov

  2. What's the catalog number I need to order this data set?

    Hh_Dd_mobility.shp: ratio of combined wave- and current-induced shear stress for Hh_Dd scenario to critical stress for sediment and various size SRBs (see SRB_classes.txt). NOTE: Specific layer name indicates the scenario (Hh_Dd) for the layer, with specific characteristics given in the included wave_scenarios.txt.

  3. What legal disclaimers am I supposed to read?

    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials.

    Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    These data are available in Environmental Systems Research Institute (ESRI) shapefile format. The user must have ArcGIS or ArcView 3.0 or greater software to read and process the data file. In lieu of ArcView or ArcGIS, the user may utilize another GIS application package capable of importing the data. A free data viewer, ArcExplorer, capable of displaying the data is available from ESRI at www.esri.com.

Who wrote the metadata?

Dates:
Last modified: 11-Dec-2012
Metadata author:
U.S. Geological Survey
c/o P. Soupy Dalyander
Oceanographer
384 Woods Hole Role
Woods Hole, MA 02543-1598
USA

(508) 548-8700 x2290 (voice)
(508) 457-2310 (FAX)
sdalyander@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.8.25 on Tue Dec 11 11:52:10 2012