SAB_mobile_freq: U.S. Geological Survey calculated recurrence interval of sediment mobility at select points in the South Atlantic Bight for May 2010 to May 2011 (point shapefile, Geographic, WGS84)

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Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator: P. Soupy Dalyander
Publication_Date: 2012
Title:
SAB_mobile_freq: U.S. Geological Survey calculated recurrence interval of sediment mobility at select points in the South Atlantic Bight for May 2010 to May 2011 (point shapefile, Geographic, WGS84)
Edition: 1.0
Geospatial_Data_Presentation_Form: vector digital data
Series_Information:
Series_Name: Database
Publication_Information:
Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA
Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
Online_Linkage:
<http://woodshole.er.usgs.gov/project-pages/mobility/ArcData/SAB_mobile_freq.zip>
Larger_Work_Citation:
Citation_Information:
Originator: P.S. Dalyander
Originator: B. Butman
Originator: C.R. Sherwood
Originator: R.P. Signell
Publication_Date: 2012
Title:
U.S. Geological Survey Sea Floor Stress and Sediment Mobility Database
Edition: 1.0
Series_Information:
Series_Name: Database
Publication_Information:
Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA
Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
Online_Linkage: <http://woodshole.er.usgs.gov/project-pages/mobility/index.html>
Description:
Abstract:
The U.S. Geological Survey has been characterizing the regional variation in shear stress on the sea floor and sediment mobility through statistical descriptors. The purpose of this project is to identify patterns in stress in order to inform habitat delineation or decisions for anthropogenic use of the continental shelf. The statistical characterization spans the continental shelf from the coast to approximately 120 m water depth, at approximately 5 km resolution. Time-series of wave and circulation are created using numerical models, and near-bottom output of steady and oscillatory velocities and an estimate of bottom roughness are used to calculate a time-series of bottom shear stress at 1-hour intervals. Statistical descriptions such as the median and 95th percentile, which are the output included with this database, are then calculated to create a two-dimensional picture of the regional patterns in shear stress. In addition, time-series of stress are compared to critical stress values at select points calculated from observed surface sediment texture data to determine estimates of sea floor mobility.
Purpose:
This GIS layer contains an estimate of the recurrence interval of sediment mobility at select points in the South Atlantic Bight. This output is based on numerical models of wave and circulation used to estimate bottom shear stress over an approximately one year time frame, which is subsequently compared to critical stress values estimated from observed surface sediment texture data. This data layer is primarily intended to show the overall distribution of sediment mobility on large spatial scales, and should be used qualitatively. Intended users include scientific researchers and the coastal and marine spatial planning community.
Supplemental_Information:
This data layer is a subset of the U.S. Geological Survey Sea Floor Stress and Sediment Mobility database, and contains the recurrence interval of sediment mobility at select points in the South Atlantic Bight. Gridded stress value (found in other layers) are calculated by interpolating wave model results to the current model grid, which may result in some water grid cells from the current model being removed and not included with the output polygons if they partially overlap land cells in the wave model. Sediment mobility statistics (such as recurrence interval) are calculated using wave and current model results at the location of the sample, therefore it is possible in some cases for a sediment mobility statistic to be calculated although it lies within a polygon with no output value, because that specific location may be within a water cell in both models while the containing current grid cell overlaps land in the wave model elsewhere in the cell.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20100501
Ending_Date: 20110501
Currentness_Reference: ground condition
Status:
Progress: Planned
Maintenance_and_Update_Frequency: As needed
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -81.816673
East_Bounding_Coordinate: -74.501671
North_Bounding_Coordinate: 38.498329
South_Bounding_Coordinate: 24.408331
Keywords:
Theme:
Theme_Keyword_Thesaurus: General
Theme_Keyword: bottom shear stress
Theme_Keyword: U.S. Geological Survey
Theme_Keyword: USGS
Theme_Keyword: Woods Hole Coastal and Marine Science Center
Theme_Keyword: WHCMSC
Theme_Keyword: Coastal and Marine Geology Program
Theme_Keyword: CMGP
Theme_Keyword: wave
Theme_Keyword: current
Theme_Keyword: SWAN
Theme_Keyword: ROMS
Theme_Keyword: Grant-Madsen
Theme_Keyword: Coastal and marine spatial planning
Theme_Keyword: CMSP
Theme_Keyword: sea floor habitat
Theme_Keyword: sediment mobility
Theme_Keyword: recurrence interval
Theme:
Theme_Keyword_Thesaurus: ISO 9115 Topic Category
Theme_Keyword: oceans
Theme_Keyword: oceans and estuaries
Theme_Keyword: oceans and coastal
Theme_Keyword: geoscientificInformation
Place:
Place_Keyword_Thesaurus: General
Place_Keyword: South Atlantic Bight
Place_Keyword: U.S. East Coast
Place_Keyword: Chesapeake Bay
Place_Keyword: United States
Place_Keyword: North America
Place_Keyword: Atlantic Ocean
Place_Keyword: Cape Canaveral
Place_Keyword: Florida Keys
Place_Keyword: Pamlico Sound
Place_Keyword: Outer Banks
Stratum:
Stratum_Keyword_Thesaurus: General
Stratum_Keyword: seafloor
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.
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: P. Soupy Dalyander
Contact_Organization: U.S. Geological Survey
Contact_Position: Oceanographer
Contact_Address:
Address_Type: mailing and physical address
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Country: USA
Contact_Voice_Telephone: (508) 548-8700 x2290
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: sdalyander@usgs.gov
Browse_Graphic:
Browse_Graphic_File_Name:
<http://woodshole.er.usgs.gov/project-pages/mobility/images/mobility_website_browse_sab_freq.jpg>
Browse_Graphic_File_Description:
Image displaying estimated recurrence interval of sediment mobility at select points in the South Atlantic Bight.
Browse_Graphic_File_Type: JPEG
Native_Data_Set_Environment:
Microsoft Windows Vista Version 6.1 (Build 7601) Service Pack 1; ESRI ArcCatalog 9.3.1.1850
Cross_Reference:
Citation_Information:
Originator: U.S. Geological Survey
Publication_Date: 2012
Title:
Documentation of the U.S. Geological Survey Sea Floor Stress and Sediment Mobility Database
Edition: 1.0
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 2012-1137
Publication_Information:
Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA
Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
Online_Linkage: <http://pubs.usgs.gov/of/2012/1137/>

Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
Each attribute in this data layer covers a specific time period of interest. The attributes include winter (December - February), spring (March - May), summer (June - August), fall (September - November), and the entire year. Each of these attributes was calculated from model output spanning May, 2010 to May, 2011. Statistical values will vary somewhat if calculated from model parameters covering a different time period, or if a different numerical model is used to estimate the time-series of waves and circulation used in calculating the time-series of bottom shear stress. Critical stress values are based on estimates made from observed surface sediment texture data, and would vary somewhat if different texture data and/or a different model of critical shear stress calculation was used.
Logical_Consistency_Report:
No duplicate features are present. All polygons are closed, and all lines intersect where intended. No undershoots or overshoots are present.
Completeness_Report:
All model output values were used in the calculation of this statistic. The statistic was calculated for the date range of May, 2010 to May, 2011, and would potentially vary somewhat if performed on a different time period. The underlying time-series of bottom shear stress was calculated from wave and current estimates generated with numerical models, and would vary if different models are used or if different model inputs (such as bathymetry or forcing winds) or parameterizations were chosen. Critical shear stress values used to estimate sediment mobility are based on observed surface sediment texture data, and mobility results would vary if different sediment texture data and/or a different model of critical shear stress were used.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Numerical models are used in the generation of time-series of bottom shear stress 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, and forcing values used, and so forth, the spatial accuracy of this data layer cannot be meaningfully quantified. These maps are intended to provide a qualitative and relative regional assessment of sea floor mobility at select points; users are advised not to use the data set to estimate mobility quantitatively at any specific geographic location, or to extrapolate mobility estimates to points not included in the database.
Lineage:
Source_Information:
Source_Citation:
Citation_Information:
Originator: NOAA National Centers for Environmental Prediction (NCEP)
Publication_Date: 20110601
Title: NOAA/NCEP Global Forecast System (GFS) Atmospheric Model
Publication_Information:
Publication_Place: Camp Springs, MD
Publisher: NOAA National Centers for Environmental Prediction
Online_Linkage: <http://nomads.ncdc.noaa.gov/data.php>
Type_of_Source_Media: online
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20100401
Ending_Date: 20110601
Source_Currentness_Reference: publication date
Source_Citation_Abbreviation: NOAA GFS
Source_Contribution:
The NOAA Global Forecast System (GFS) 0.5 degree model was used to provide wind speed data at 10 m above the sea surface to drive the numerical wave model used to generate bottom orbital wave velocities for calculations of a time-series of bottom shear stress.
Source_Information:
Source_Citation:
Citation_Information:
Originator: NOAA National Centers for Environmental Prediction (NCEP)
Publication_Date: 20110601
Title: NOAA/NCEP North American Mesoscale (NAM) Atmospheric Model
Publication_Information:
Publication_Place: Camp Springs, MD
Publisher: NOAA National Centers for Environmental Prediction
Online_Linkage: <http://nomads.ncdc.noaa.gov/data.php>
Type_of_Source_Media: online
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20100401
Ending_Date: 20110601
Source_Currentness_Reference: publication date
Source_Citation_Abbreviation: NOAA NAM
Source_Contribution:
The NOAA North American Mesoscale (NAM) model was used to provide wind speed data at 10 m above the sea surface to drive the numerical wave model used to generate bottom orbital wave velocities for calculations of a time-series of bottom shear stress.
Source_Information:
Source_Citation:
Citation_Information:
Originator: North Carolina State University
Publication_Date: 2012
Title:
South Atlantic Bight and Gulf of Mexico Circulation Nowcast/Forecast (SABGOM N/F)
Publication_Information:
Publication_Place: Raleigh, NC
Publisher: North Carolina State University
Online_Linkage: <http://omglnx6.meas.ncsu.edu/sabgom_nfcast/>
Type_of_Source_Media: CD-ROM
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20100501
Ending_Date: 20110501
Source_Currentness_Reference: publication date
Source_Citation_Abbreviation: SABGOM
Source_Contribution:
The North Carolina State University (NCSU) SABGOM model was used to provide estimates of near-bed current velocity used for calculating the time-series of bottom shear stress.

The SABGOM hydrodynamic model (<http://omglnx6.meas.ncsu.edu/sabgom_nfcast/>) is operated by North Carolina State University as a quasi-operational nowcast/forecast system in the Southeast Coastal Ocean Observing Regional Association (SECOORA, <http://secoora.org/>), part of the U.S. Integrated Ocean Observing System (<http://www.ioos.gov>). The underlying circulation model is the Regional Ocean Modeling System (ROMS; <http://www.myroms.org>), a finite-difference, hydrostatic, primitive equation ocean model that solves for the free surface elevation and three dimensional flow patterns, temperature, and salinity.

The SABGOM configuration of ROMS has 5 km horizontal resolution and 36 layers in vertical terrain-following coordinates. Ocean open boundary values are from a global forecast that uses the HYbrid Coordinate Ocean Model (HyCOM) with assimilation of satellite and in situ data with the Navy Coupled Ocean Data Assimilation (NCODA) system. Tidal harmonic boundary variability is determined from a regional tidal model.

The datafiles for the time period used in this analysis were acquired directly from Dr. Ruoying He of NCSU.

Source_Information:
Source_Citation:
Citation_Information:
Originator: NOAA National Centers for Environmental Prediction (NCEP)
Publication_Date: 20110601
Title: NOAA/NWS/NCEP Global Wavewatch III Operational Wave Forecast
Publication_Information:
Publication_Place: Camp Springs, MD
Publisher: NOAA National Centers for Environmental Prediction
Online_Linkage: <http://polar.ncep.noaa.gov/waves/index2.shtml>
Type_of_Source_Media: online
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20100401
Ending_Date: 20110601
Source_Currentness_Reference: publication date
Source_Citation_Abbreviation: NOAA WW3
Source_Contribution:
Boundary conditions for the wave model were provided by the global NOAA/NWS/NCEP Wavewatch III operational ocean wave forecast.
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey
Publication_Date: 2011
Title:
ECSTDB2011.xls: U.S. Geological Survey East Coast Sediment Texture Database (2011)
Edition: 2.2
Geospatial_Data_Presentation_Form: spreadsheet
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 2005-1001
Publication_Information:
Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA
Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
Other_Citation_Details:
At the time the data were taken for this study, the surficial sediment texture data had been updated to include samples analyzed through January, 2011.
Online_Linkage:
<http://pubs.usgs.gov/of/2005/1001/data/surficial_sediments/ecstdb2011.xls>
Online_Linkage: <http://pubs.usgs.gov/of/2005/1001/htmldocs/datacatalog.htm>
Larger_Work_Citation:
Citation_Information:
Originator: L.J. Poppe
Originator: S.J. Williams
Originator: V.F. Paskevich
Publication_Date: 2005
Title:
USGS East-Coast Sediment Analysis: Procedures, Database, and GIS Data
Edition: 1.0
Geospatial_Data_Presentation_Form: spreadsheet
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 2005-1001
Publication_Information:
Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA
Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
Online_Linkage: <http://pubs.usgs.gov/of/2005/1001/>
Type_of_Source_Media: online
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2011
Source_Currentness_Reference: publication date
Source_Citation_Abbreviation: USGS ECSTD
Source_Contribution:
Critical stress threshold values were calculated from surface sediment texture data found in the U.S. Geological Survey East-Coast Sediment Texture Database
Process_Step:
Process_Description:
The WavewatchIII (WW3) numerical wave model (v3.14) was run on both a global 30' and regional North Atlantic 10' grid. The global grid is identical to the one used by the NOAA WW3 forecast system, whereas the regional grid is based on the NOAA WW3 grid but was modified slightly to remove parts of the "do not compute" mask at the outer boundaries where output was needed to pass to the nested, higher resolution grid. WW3 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. The model was identically configured to the multi-grid system set-up used by the NOAA WW3 operational forecast (more information at <http://polar.ncep.noaa.gov/waves/index2.shtml>), and was rerun purely to generate full spectra boundary conditions at the boundaries of the higher resolution nested domain. Wind forcing was provided at 3-hour resolution from the NOAA North American Mesoscale (NAM) model (12 km resolution) over its domain, with the rest of the domain (outside the NAM grid) provided by the NOAA Global Forecasting System (GFS) model at 0.5 degree resolution.
Source_Used_Citation_Abbreviation: NOAA GFS
Source_Used_Citation_Abbreviation: NOAA NAM
Source_Used_Citation_Abbreviation: NOAA WW3
Process_Date: 2012
Source_Produced_Citation_Abbreviation: WW3
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: P. Soupy Dalyander
Contact_Organization: U.S. Geological Survey
Contact_Position: Oceanographer
Contact_Address:
Address_Type: mailing and physical address
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Country: USA
Contact_Voice_Telephone: (508) 548-8700 x2290
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: sdalyander@usgs.gov
Process_Step:
Process_Description:
The Simulating WAves Nearshore (SWAN) numerical wave model (version 40.81, modified for proper calculation of RMS bottom orbital velocity and for output of bottom wave direction) was used to create a time-series of bottom orbital velocity, bottom representative period, and bottom wave direction over the one year time period of May, 2010 - May, 2011 in each grid cell in the model domain. The wave model SWAN 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. Although stress calculations were only performed over the spatial extent of the hydrodynamic model, SWAN was run over a larger spatial scale. The model domain consists of seven overlapping regular numerical model grids that follow the eastern and Gulf of Mexico coasts of the United States at approximately 3.5 km resolution. The model was run for April 2010 using the default SWAN initial condition formulation for a non-stationary run, e.g., a JONSWAP spectrum from prescribed initial wind conditions, to develop initial conditions for the one year study period (May 2010 to May 2011).

Full spectra boundary conditions at each model ocean boundary point are interpolated from the output of the regional 10' Wavewatch III model, updated every hour. Wind forcing was provided at 3-hour resolution from the NOAA North American Mesoscale (NAM) model (12 km resolution) over its domain, with forcing at the most offshore portions of the grid (outside the NAM grid) provided by the NOAA Global Forecasting System (GFS) model at 0.5 degree resolution. The SWAN directional resolution was 6 degrees (60 bins), determined via sensitivity analysis as the coarsest (and hence least computationally expensive) resolution that does not result in the "Garden-Sprinkler Effect" (GSE), wherein swell traveling over large distances inaccurately disintegrates into non-continuous wave fields as a result of frequency and directional discretization. The minimum frequency bin should be set to a value less than 0.7 times the lowest expected peak frequency and the maximum frequency bin should be set at least 2.5-3 times the highest expected peak frequency expected. In order to determine appropriate values, the peak periods from 43 NDBC buoys throughout the wave model domain were analyzed (when available) over the one year period of the study, yielding 297,533 hourly observations. The 99th and 1st percentiles of peak period were 15 s and 3 s, corresponding to frequencies of 0.07 Hz and 0.33 Hz, noting that these values may be biased by buoy limits of detection at high and low frequencies. The frequency range was therefore specified as 0.04-1 Hz. SWAN was allowed to internally determine the frequency resolution as one tenth of each frequency bin for best performance of the discrete interaction approximation (DIA) method of nonlinear 4-wave interactions, resulting in 34 frequency bins. Bottom friction calculations used the Madsen formulation with a uniform roughness length scale of 0.05 m. This value was selected for the best comparison of model output and buoy observations within the domain, and does not correspond to physical roughness values or the bottom roughness used in stress calculations. Wind generation and whitecapping parameterizations follow the modified Komen approach prescribed by Rogers et al. (2003), which reduces inaccurate attenuation of swell energy by whitecapping. Wave model outputs of bottom orbital velocity, bottom representative period, and bottom wave direction were output hourly and interpolated onto the SABGOM model grid.

The same person that conducted this processing step conducted each subsequent processing step.

References:

Rogers, W.E., Hwang, P.A., Wang, D.W., 2003. Investigation of Wave Growth and Decay in the SWAN Model: Three Regional-Scale Applications. J. Phys. Oceanogr. 33, 366-389.

Source_Used_Citation_Abbreviation: NOAA GFS
Source_Used_Citation_Abbreviation: NOAA NAM
Source_Used_Citation_Abbreviation: WW3
Process_Date: 2011
Source_Produced_Citation_Abbreviation: SWAN WEST ATL
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: P. Soupy Dalyander
Contact_Organization: U.S. Geological Survey
Contact_Position: Oceanographer
Contact_Address:
Address_Type: mailing and physical address
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Country: USA
Contact_Voice_Telephone: (508) 548-8700 x2290
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: sdalyander@usgs.gov
Process_Step:
Process_Description:
Use observed surficial sediment texture data to estimate the critical shear stress at those points where sediment texture data are available. Calculations are performed in Mathworks MATLAB (v2011A). The texture data includes the distribution of sediment over grain size classes ranging from -5 to 11 phi, ranging from gravel through sand and silt to clay. Texture observations are first classified as cohesive or non-cohesive based on the fraction of clay: if the clay fraction exceeds 7.5%, the sample is deemed cohesive, if less than or equal to 7.5% the sample is non-cohesive. Critical stress thresholds for non-cohesive sediment mixtures are calculated from the median grain size following Soulsby (1997). Because a variety of unavailable parameters influence the critical shear stress for cohesive sediments, a value of 0.1 Pa is used for all samples identified as cohesive. Although the density of sediment in the South Atlantic Bight can vary, analysis determined that the resultant variability in critical stress is small compared to the influence of particle size, and an assumed density value of 2650 kg/m3 (quartz) was used to allow inclusion of samples lacking composition information. Critical stress values, median grain sizes, and classifications as cohesive or non-cohesive at each location are saved in MATLAB .mat format. Additional information may be found in Dalyander et al. (2012).

References:

Dalyander, P.S., Butman, B., Sherwood, C.R., and Signell, R.P. (2012). Documentation of the U.S. Geological Survey Seafloor Stress and Sediment Mobility Database. USGS OFR 2012-1137.

Soulsby, R., 1997. Dynamics of Marine Sands, a Manual for Practical Applications. Thomas Telford Publications, London.

Source_Used_Citation_Abbreviation: USGS ECSTD
Process_Date: 2011
Source_Produced_Citation_Abbreviation: USGS ECSTD MAT
Process_Step:
Process_Description:
Use the wave model and current model results to calculate the time series of bottom shear stress at each point for which sediment texture data are available using Mathworks MATLAB software (v2011A). Bottom shear stress estimates are made following Grant-Madsen (GM) (Madsen, 1994), from the estimated bottom orbital velocities and bottom wave periods generated with SWAN, and near-bed current estimates from the ESPreSSO hydrodynamic model. The GM approach relies on an eddy viscosity turbulence closure model and formulates the wave stress, current stress, and combined wave-current bottom stress as functions of a representative bottom wave orbital velocity, representative bottom wave period, current flow at some reference height, the angle between wave and current propagation, and bottom roughness. Full details of the GM formulation may be found elsewhere (Glenn, 1983; Glenn and Grant, 1987; Grant and Madsen, 1979, 1982, 1986; Madsen, 1994; Madsen et al., 1988).

Wave direction, bottom orbital velocities, and bottom periods are calculated internally by the wave model. Near-bed current magnitude and direction are taken from the hydrodynamic model, with the reference height taken as the distance from the cell vertical midpoint to the seabed. GM requires that the current velocity be taken above the wave boundary layer (WBL) but within the log-profile current velocity layer. If the thickness of the WBL calculated using GM exceeds of one or more of the deepest grid cells, the current estimate and associated reference height are used from the deepest grid cell at each location where the reference height exceeds the width of the WBL. An estimate must be used for the maximum reference height where the log-profile velocity layer assumption is valid. As discussed in Grant and Madsen (1986), the thickness of the log-profile layer based on laboratory experiments is approximately 10% of the current boundary layer thickness (Clauser, 1956). Because tidal currents, storm currents, and mean flow have a boundary layer thickness on the order of magnitude 10's of meters (Goud, 1987), a maximum value for reference height is set as 5 m.

The GM bottom boundary layer model also requires a value for bottom roughness. For the mobility estimates, it is the skin friction acting on the particles, and not the total bottom shear stress, which is the relevant parameter. For that reason, observed sediment texture data from the USGS East Coast Sediment Texture Database (v2.2) are used to calculate the bottom roughness at each point for which they are available. For non-cohesive samples (see definition in Process Step 2), the median grain size is used as the roughness. For cohesive samples a roughness of 62.5 micrometers, which has a critical stress based on Soulsby (1997) of 0.1 Pa, is used.

References:

Clauser, F.H., 1956. The turbulent boundary layer. Adv. Appl. Mech. 4, 1-51.

Madsen, O.S., 1994. Spectral wave-current bottom boundary layer flows, Proceedings 24th Conf. Coastal Eng., pp. 384-398.

Glenn, S.M., 1983. A Continental Shelf Bottom Boundary Layer Model: The Effects of Waves, Currents, and a Moveable Bed. Dissertation, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, Cambridge, MA, 237 pp.

Glenn, S.M., Grant, W.D., 1987. A suspended sediment stratification correction for combined wave and current flows. J. Geophys. Res. 92, 8244-8264.

Goud, M.R., 1987. Prediction of Continental Shelf Sediment Transport Using a Theoretical Model of the Wave-Current Boundary Layer. Dissertation, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, Cambridge, MA, 211 pp.

Grant, W.D., Madsen, O.S., 1986. The continental-shelf bottom boundary-layer. Annu. Rev. Fluid Mech. 18, 265-305.

Grant, W.D., Madsen, O.S., 1982. Movable bed roughness in unsteady oscillatory flow. J. Geophys. Res. 87, 469-481.

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

Madsen, O.S., 1994. Spectral wave-current bottom boundary layer flows, Proceedings 24th Conf. Coastal Eng., pp. 384-398.

Madsen, O.S., Poon, Y., Graber, H.C., 1988. Spectral wave attenuation by bottom friction: theory, Proceedings 21st Int. Conf. Coast. Eng., pp. 492-504.

Soulsby, R., 1997. Dynamics of Marine Sands, a Manual for Practical Applications. Thomas Telford Publications, London.

Source_Used_Citation_Abbreviation: SWAN WEST ATL
Source_Used_Citation_Abbreviation: SABGOM
Source_Used_Citation_Abbreviation: USGS ECSTD MAT
Process_Date: 2011
Source_Produced_Citation_Abbreviation: STRESS TSERIES
Process_Step:
Process_Description:
Calculate the recurrence interval of sediment mobility by year and season in Mathworks MATLAB software (v2011A) by comparing the critical stress value at each point location where sediment texture data are available to the time series of combined wave-current stress at that location. A bed mobility event was identified by exceedance of the critical stress threshold for at least 2 hours, with no minimum separation time between events. The recurrence interval is calculated as the length of the time period (in days) of interest (e.g., year or season) divided by the number of events during that time period. These values are saved in MATLAB .mat format.
Source_Used_Citation_Abbreviation: STRESS TSERIES
Source_Used_Citation_Abbreviation: USGS ECSTD MAT
Process_Date: 2011
Source_Produced_Citation_Abbreviation: RECURR
Process_Step:
Process_Description:
Export the point values from MATLAB format into an ArcGIS shapefile using the Mathworks MATLAB Mapping Toolbox (v2011A). In some cases, data may exist during parts of the year and not others (for example, if no events are observed in a particular time period, resulting in a non-realistic recurrence interval of infinity); in this case, the statistic is calculated and included for the season where model output exist, and a missing data value of -9999 is used for seasons where no valid statistic can be calculated. A geographic data structure is created in MATLAB with the following fields: Geometry ('Point'), Lon (the longitude at the point), Lat (the latitude at the point), Winter (the statistic calculated for December, January, and February), Spring (the statistic calculated for March, April, and May), Summer (the statistic calculated for June, July, and August), and Fall (the statistic calculated for September, October, and November). The shapefile is then 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.
Source_Used_Citation_Abbreviation: RECURR
Process_Date: 2011

Spatial_Data_Organization_Information:
Indirect_Spatial_Reference: South Atlantic Bight
Direct_Spatial_Reference_Method: Vector
Point_and_Vector_Object_Information:
SDTS_Terms_Description:
SDTS_Point_and_Vector_Object_Type: Entity point
Point_and_Vector_Object_Count: 1498

Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Geographic:
Latitude_Resolution: 0.000001
Longitude_Resolution: 0.000001
Geographic_Coordinate_Units: Decimal degrees
Geodetic_Model:
Horizontal_Datum_Name: D_WGS_1984
Ellipsoid_Name: WGS_1984
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.257224

Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: SAB_mobile_freq
Entity_Type_Definition: Shapefile Attribute Table
Entity_Type_Definition_Source: Esri
Attribute:
Attribute_Label: FID
Attribute_Definition: Internal feature number.
Attribute_Definition_Source: Esri
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label: Shape
Attribute_Definition: Feature geometry.
Attribute_Definition_Source: Esri
Attribute_Domain_Values:
Unrepresentable_Domain: Coordinates defining the features.
Attribute:
Attribute_Label: Year
Attribute_Definition:
This value is the recurrence interval of sediment mobility at point locations calculated for the one year time period of May 1, 2010 through April 30, 2011. The NODATA value is -9999.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.2834
Range_Domain_Maximum: 365
Attribute_Units_of_Measure: days
Attribute_Measurement_Resolution: 0.0001
Attribute:
Attribute_Label: Winter
Attribute_Definition:
This value is the recurrence interval of sediment mobility at point locations calculated for the period of December 1, 2010 through February 28, 2011. The NODATA value is -9999.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.2932
Range_Domain_Maximum: 90
Attribute_Units_of_Measure: days
Attribute_Measurement_Resolution: 0.0001
Attribute:
Attribute_Label: Spring
Attribute_Definition:
This value is the recurrence interval of sediment mobility at point locations calculated for the period of March 1, 2011, through April 30, 2011, and May, 2010. The NODATA value is -9999.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.2874
Range_Domain_Maximum: 91.9583
Attribute_Units_of_Measure: days
Attribute_Measurement_Resolution: 0.0001
Attribute:
Attribute_Label: Summer
Attribute_Definition:
This value is the recurrence interval of sediment mobility at point locations calculated for the period of June 1, 2010, through August 31, 2010. The NODATA value is -9999.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.2659
Range_Domain_Maximum: 92
Attribute_Units_of_Measure: days
Attribute_Measurement_Resolution: 0.0001
Attribute:
Attribute_Label: Fall
Attribute_Definition:
This value is the recurrence interval of sediment mobility at point locations calculated for the period of September 1, 2010, to November 30, 2010. The NODATA value is -9999.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.2809
Range_Domain_Maximum: 91
Attribute_Units_of_Measure: days
Attribute_Measurement_Resolution: 0.0001

Distribution_Information:
Distributor:
Contact_Information:
Contact_Person_Primary:
Contact_Person: P. Soupy Dalyander
Contact_Organization: U.S. Geological Survey
Contact_Position: Oceanographer
Contact_Address:
Address_Type: mailing and physical address
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Country: USA
Contact_Voice_Telephone: (508) 548-8700 x2290
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: sdalyander@usgs.gov
Resource_Description:
Downloadable Data: Sea Floor Stress and Sediment Mobility Database, Recurrence Interval of Sediment Mobility for the South Atlantic Bight (SAB_mobile_freq)
Distribution_Liability:
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.

Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: SHP
Format_Version_Number: 3.3
Format_Specification: Esri shapefile
Format_Information_Content:
WinZip archive file containing the shapefile components. The WinZip file also includes FGDC compliant metadata.
File_Decompression_Technique: WinZip 12.0 archive
Transfer_Size: 0.040
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name:
<http://woodshole.er.usgs.gov/project-pages/mobility/south_atl_bight.html>
Network_Resource_Name:
<http://woodshole.er.usgs.gov/project-pages/mobility/ArcData/SAB_mobile_freq.zip>
Network_Resource_Name: <http://woodshole.er.usgs.gov/project-pages/mobility/index.html>
Fees: None
Technical_Prerequisites:
These data are available in 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.

Metadata_Reference_Information:
Metadata_Date: 20121217
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: P. Soupy Dalyander
Contact_Position: Oceanographer
Contact_Address:
Address_Type: mailing and physical address
Address: 384 Woods Hole Role
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Country: USA
Contact_Voice_Telephone: (508) 548-8700 x2290
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: sdalyander@usgs.gov
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Time_Convention: local time
Metadata_Access_Constraints: None
Metadata_Use_Constraints: None
Metadata_Extensions:
Online_Linkage: <http://www.esri.com/metadata/esriprof80.html>
Profile_Name: ESRI Metadata Profile

Generated by mp version 2.8.25 on Mon Dec 17 13:21:09 2012