Projected Seafloor Elevation Change and Relative Sea Level Rise Near St. Croix, U.S. Virgin Islands 25, 50, 75, and 100 Years from 2014

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Frequently anticipated questions:


What does this data set describe?

Title:
Projected Seafloor Elevation Change and Relative Sea Level Rise Near St. Croix, U.S. Virgin Islands 25, 50, 75, and 100 Years from 2014
Abstract:
The U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center conducted research to quantify bathymetric changes near Buck Island and St. Croix, U.S. Virgin Islands. Changes in seafloor elevation were calculated using historical bathymetric point data from the 1980s (see Yates and others, 2017a) and light detection and ranging (lidar)-derived data acquired in 2014 (NOAA, 2015) using methods outlined in Yates and others (2017b). An elevation change analysis between the 1980s and 2014 data was performed to quantify and map historical impacts to seafloor elevation and to determine elevation-change statistics for 12 habitat types found near St. Croix. Annual elevation-change rates were calculated for each elevation-change data point. Seafloor elevation-change near St. Croix was projected 25, 50, 75 and 100 years from 2014 using these historical annual rates of elevation change. Water depth was projected 25, 50, 75 and 100 years from 2014 using historical rates of annual elevation change plus 2014 local sea level rise (SLR) data from the National Oceanic and Atmospheric Administration (NOAA).
Supplemental_Information:
Elevation measurements were collected over St. Croix and St. Thomas using the National Aeronautics and Space Administration (NASA) Experimental Advanced Airborne Research Lidar (EAARL) system, a pulsed laser ranging system mounted onboard an aircraft to measure ground elevation, vegetation canopy, and coastal topography. The system uses high-frequency laser beams directed at the Earth's surface through an opening in the bottom of the aircraft's fuselage. The laser system records the time difference between emission of the laser beam and the reception of the reflected laser signal in the aircraft. For more information, see the NOAA metadata file available at, https://www.fisheries.noaa.gov/inport/item/48140. Relative sea level rise (RSLR) trend data were retrieved from the NOAA Tides and Currents portal via Station 9751401 at Lime Tree Bay, Virgin Islands (NOAA, 2020).
  1. How might this data set be cited?
    Yates, Kimberly K., and Fehr, Zachery W., 20220321, Projected Seafloor Elevation Change and Relative Sea Level Rise Near St. Croix, U.S. Virgin Islands 25, 50, 75, and 100 Years from 2014:.

    This is part of the following larger work.

    Yates, Kimberly K., and Fehr, Zachery W., 20220321, Projected Seafloor Elevation Change and Relative Sea Level Rise Near St. Croix, U.S. Virgin Islands 25, 50, 75, and 100 Years from 2014: U.S. Geological Survey data release doi:10.5066/P9ZPZXKF, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -64.649510
    East_Bounding_Coordinate: -64.429511
    North_Bounding_Coordinate: 17.840630
    South_Bounding_Coordinate: 17.749476
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1981
    Ending_Date: 2114
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: Tabular and vector digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set.
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 20
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -63.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.6096
      Ordinates (y-coordinates) are specified to the nearest 0.6096
      Planar coordinates are specified in METERS
      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is GRS_1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: Virgin Islands Vertical Datum of 2009
      Altitude_Resolution: 0.2
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    The detailed attribute descriptions for the elevation change data, projected elevation change analysis, and habitat definitions are provided in the included data dictionaries (DataDictionary_Shapefile_STC.pdf, DataDictionary_HabitatTypes_STC.pdf, and DataDictionary_ElevationChangeAnalysis_STC.pdf). These metadata are not complete without these files.
    Entity_and_Attribute_Detail_Citation:
    The entity and attribute information were generated by the individual and/or agency identified as the originator of the dataset. Please review the rest of the metadata record for additional details and information.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Kimberly K. Yates
    • Zachery W. Fehr
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Kimberly K. Yates
    Southeast Region: ST. PETE COASTAL & MARINE SC
    Research Oceanographer
    600 4Th Street South
    St. Petersburg, FL
    United States

    727-502-8059 (voice)
    kyates@usgs.gov

Why was the data set created?

These data were used to generate projected elevation-change and water depth values surrounding St. Croix, Virgin Islands for twelve habitat types located within the study area.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 2020 (process 1 of 6)
    Step 1: Seafloor elevation change analyses were performed using methods described in Yates and others (2017b). The STC_ElevationChange.csv file was downloaded from Yates and others (2017a) data release and was imported into ArcMap 10.7 to create a point shapefile named STC_SeafloorElevationChangePoints.shp. Original column headers in the .csv data were too long for shapefile attribute names, so attributes were either renamed or deleted if not required. The historical sounding elevation data corrected for SLR, 2014 lidar elevation data, longitude, latitude, and hydrographic sheet information attributes were renamed to HistE_SLRc, 2014_elev, POINT_X, POINT_Y, and Survey, respectively. A new attribute was added to this shapefile and named 'Rate' and values were populated in the field by using the Field Calculator and the following expression: Rate = [Diff_m]/(2014-[Year]), where [Diff_m] is the elevation difference between the historical hydrographic data and modern lidar data and [Year] is the attribute value containing the hydrographic survey collection year.
    Date: 2020 (process 2 of 6)
    Step 2: The habitat shapefile used in this analysis was downloaded from NOAA's National Centers for Coastal Ocean Science Data Collection site (NOAA, 2001). The original shapefile, stc_fin.shp, was renamed to STC_Habitat.shp. The elevation-change dataset extended beyond the bounds of the available habitat data. An additional polygon was incorporated into the shapefile during an edit session to account for this discrepancy. The additional polygon was given the 'Unclassified' habitat class in the 'TYPE' attribute field. The 'TYPE' attribute was used in this analysis, which had the most similar definition to other US coral reef habitat maps. The habitat shapefile was then exported as STC_Habitat_UnclassifiedAdded.shp. Further information on the attributes and their definitions can be found in the DataDictionary_HabitatTypes_STC.pdf file in the STC_HabitatShapefile.zip download file
    Date: 2020 (process 3 of 6)
    Step 3: Additional fields were added to the attribute table to represent projected elevations (N_e) based on elevation change rates, projected elevation change (N_e_diff) based on N_e elevations, projected water depth (N_WDepth) after accounting for RSLR and projected elevation change, and relative sea level rise (N_RSLR) based on NOAA SLR rates and projected elevation change rates, where N represents the number of years projected from the collection date of the most recent bathymetry used in the analysis: 25_e, 50_e, 75_e, 100_e, 25_e_diff, 50_e_diff, 75_e_diff, 100_e_diff, 25_WDepth, 50_WDepth, 75_WDepth, 100_WDepth, 25_RSLR, 50_RSLR, 75_RSLR, and 100_RSLR. The Field Calculator was used to populate values for each of these attributes using the following equations: N_e = [2014_elev]+(N*[Rate]), N_e_diff = [N_e]-[2014_elev], N_WDepth = Abs([2014_elev]+(N*[Rate]))+(N*0.00229), and N_RSLR = (N*0.00229)–[N_e_diff]. The shapefile was then exported as STC_ProjectedElevationChangePoints_25yr_50yr_75yr_and_100yr_from_2014.shp. Further information on the attributes and their definitions can be found in the DataDictionary_Shapefile_STC.pdf file in the STC_ProjectedElevationChangePoints_25yr_50yr_75yr_and_100yr_from_2014.zip download file.
    Date: 2020 (process 4 of 6)
    Step 4: A visual inspection of the projected elevation change data and comparison to existing aerial imagery was conducted and erroneous elevation change points were removed using methods of Yates et al., 2017b. Additional points were identified for visual inspection and potential removal using the select features tool and a demarcating Rate value of +/- 0.20 m per year in ArcMap 10.7. Any point that was subaerial at the 100-year water depth projection (100_WDepth) was also selected and removed. These points were assumed to be due to substantial sediment transport events such as landslides and slumps that occur on these dynamic shorelines. Satellite imagery and topographic maps from various time periods were used in determining likely landslide and slump activity at these points.
    Date: 2020 (process 5 of 6)
    Step 5: Elevation change statistics were determined for each habitat type using the XYZ points from the STC_ProjectedElevationChangePoints_25yr_50yr_75yr_and_100yr_from_2014.shp shapefile. The "Select Layer by Location (Data Management)" tool was used to extract points within or on the boundary of a specific habitat type by using the following parameters: Input Feature Layer: STC_ProjectedElevationChangePoints_25yr_50yr_75yr_and_100yr_from_2014.shp shapefile; Relationship: INTERSECT; Selecting Features: STC_Habitat_UnclassifiedAdded.shp shapefile; Search Distance: left blank; and Selection type: NEW_SELECTION. The Seafloor Elevation Change Analysis Tool (SECAT) was created to automate the process, since these steps had to be repeated for 12 habitat types under 5 different scenarios: one between historical hydrographic data and contemporary lidar data (diff_m), and one for each N_e_diff attribute. Elevation change statistics were compiled by habitat type into the following comma-separated values (CSV) files: STC_Historical.csv, STC_25e.csv, STC_50e.csv, STC_75e.csv, and STC_100e.csv. Entries that do not have a large enough sample size to compute statistics display "N/A" in the associated cell. These statistics can be found in STC_ProjectedSECAT.zip. For more information on SECAT and its capabilities see Zieg and Zawada (2021). Further information on the attributes and their definitions can be found in the DataDictionary_HabitatTypes_STC.pdf and DataDictionary_ElevationChangeAnalysis_STC.pdf files in the STC_ProjectedSECAT.zip download file.
    Date: 2020 (process 6 of 6)
    Step 6: Maps were rendered for each projected change attribute calculated in Step 3. Maps appended in ‘N_e_diff' depict projected elevation change at each point N years into the future. Projected RSLR maps that consider projected elevation change analyses were developed using separate symbology palettes and were appended ‘N_RSLR,’ respectively. All maps are available within the STC_ProjectionMaps.zip download file.
  3. What similar or related data should the user be aware of?
    Yates, Kimberly K., Zawada, David G., Smiley, Nathan A., Tiling-Range, Ginger, and Resnick, Jessica P., 20170308, Seafloor elevation change in Maui, St. Croix, St. Thomas, and the Florida Keys: U.S. Geological Survey data release doi:10.5066/F7WQ01W0, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

    Online Links:

    Other_Citation_Details: 2017a
    Yates, Kimberly K., Zawada, David G., Smiley, Nathan A., and Tiling-Range, Ginger, 20170420, Divergence of seafloor elevation and sea level rise in coral reef ecosystems: Biogeosciences, Munich, Germany.

    Online Links:

    Other_Citation_Details: 2017b
    Zieg, Jonathan A., and Zawada, David G., 20210211, Seafloor elevation change analysis tool: U. S. Geological Survey, St. Petersburg, Florida.

    Online Links:

    NOAA Office for Coastal Management (OCM), 20150725, EAARL-B submerged topography - Saint Croix and Saint Thomas, U.S. Virgin Islands, 2014: NOAA, Charleston, South Carolina.

    Online Links:

    NOAA Tides & Currents, 20200801, Lime Tree Bay, VI - station ID: 9751401: NOAA, Washington, D.C..

    Online Links:

    NOAA National Ocean Service (NOS), 20010319, Polygon shapefiles - St Croix: NOAA Coastal Services Center, Charleston, South Carolina.

    Online Links:


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

  1. How well have the observations been checked?
    Digital elevation maps were visually inspected by cross-checking them with other contemporary, overlapping datasets such as satellite and airborne imagery and/or other digital elevation maps in Esri ArcGIS for identification of anomalous elevations or data inconsistencies.
  2. How accurate are the geographic locations?
    Raw elevation measurements have been determined to be within 1 meter (m) in horizontal accuracy.
  3. How accurate are the heights or depths?
    The nominal vertical elevation accuracy expressed as the root mean square error (RMSE) for the point elevation data is 13.5 centimeters (cm).
  4. Where are the gaps in the data? What is missing?
    This dataset is considered complete for the information presented, as described in the abstract section. Users are advised to read the rest of the metadata record and Yates and others (2017b) for additional details.
  5. How consistent are the relationships among the observations, including topology?
    Data cover the area specified for this project, without any known issues.

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. The U.S. Geological Survey requests to be acknowledged as originator of these data in future products or derivative research.
  1. Who distributes the data set? (Distributor 1 of 1)
    Kimberly K. Yates
    Southeast Region: ST. PETE COASTAL & MARINE SC
    Research Oceanographer
    600 4Th Street South
    St. Petersburg, FL
    United States

    727-502-8059 (voice)
    kyates@usgs.gov
  2. What's the catalog number I need to order this data set?
  3. What legal disclaimers am I supposed to read?
    Although these data have been processed successfully on a computer system at the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The USGS shall not be held liable for improper or incorrect use of the data described or contained herein. Any use of trade, firm, or product 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?

Who wrote the metadata?

Dates:
Last modified: 21-Mar-2022
Metadata author:
Kimberly K. Yates
Southeast Region: ST. PETE COASTAL & MARINE SC
Research Oceanographer
600 4Th Street South
St. Petersburg, FL
United States

727-502-8059 (voice)
kyates@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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