Timbalier Islands, Gulf Side Transects

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Frequently-anticipated questions:

What does this data set describe?

    Title: Timbalier Islands, Gulf Side Transects
    The U.S. Geological Survey (USGS), in cooperation with the Coastal Research Laboratory in the Department of Geology and Geophysics at the University of New Orleans (UNO) and the Center for Coastal Energy and Environmental Resources at Louisiana State University (LSU), is investigating the processes of coastal erosion and wetland loss in Louisiana (Sallenger and others, 1987; Sallenger and Williams 1989; Penland and others, 1992).

    Building on the USGS Louisiana Barrier Island Study (Williams and others, 1992), this data layer depicts the shore-normal transects used to measure shoreline change.

    The Timbalier Islands are located about 100 km south-southwest of New Orleans. This barrier island shoreline is 30 km long and extends east from Cat Island Pass to Raccoon Pass. The Timbalier Islands represent a flanking barrier island system developed from the reworking and erosion of an abandoned distributary of the Lafourche delta complex within the Mississippi River delta plain (Penland and others, 1988). Island evolution is driven by predominant longshore sediment transport and storm overwash, causing the island arc to migrate to the north and west. The present configuration of the Timbalier Islands consists of Timbalier Island to the west, Timbalier Shoal, and East Timbalier Island to the east. Timbalier Shoal, located between the two islands within Little Pass Timbalier, is a transient area of moving sand, which is subaerial for some periods of measurement. The Gulf shoreline of East Timbalier Island has been armored by a rock seawall with a second seawall constructed landward in an attempt to protect oil and gas facilities on the bayside.

    In order to quantify shoreline changes since January 21, 1988, new vertical aerial mapping photography was acquired on December 9, 1996 The methods and transects used by McBride and others (1992) were used to insure data compatibility of the new measurements and analysis

    To evaluate change in the shoreline position, shore-normal transects were constructed at approximately 15-second intervals of longitude or latitude depending on shoreline orientation. Isles Dernieres, Bayou Lafourche and Plaquemines barrier systems (east-west shroelines) were analyzed using 15-second (about 404 m) intervals of longitude, while the Chandeleur Islands (north-south shorelines) were examined by using 15-second (about 462 m) intervals of latitude. Measurements of shoreline movement and change in island width were taken along transects perpendicular to the composite shoreline trend. Average rates of movement and area change were calculated by dividing absolute measurements by elapsed time (year, month, and day - where available.) Shoreline change maps were procuded to determine the spatial and temporal distribution of shoreline movement (magnitude, direction, and rate of change) and document geomorphologic evolution. (McBride and others, 1992).

  1. How should this data set be cited?

    Reid, Jamey M. , 2003, Timbalier Islands, Gulf Side Transects: U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Field Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Williams, S.J., Reid, J.M., Cross, V., and Polloni, C., 2003, Coastal Erosion and Wetland Change in Louisiana: Selected USGS Products: Digital Data Series DDS-79, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Field Center Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -90.550444
    East_Bounding_Coordinate: -90.200499
    North_Bounding_Coordinate: 29.097626
    South_Bounding_Coordinate: 29.035206

  3. What does it look like?

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

    Calendar_Date: 1996
    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?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • String (85)

    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 0.000000. Longitudes are given to the nearest 0.000000. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.

  7. How does the data set describe geographic features?


    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Feature geometry. (Source: ESRI)

    Coordinates defining the features.







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?

    University of New Orleans
    c/o Paul Connor, Jr
    Dept. of Geology & Geophysics, Pontchartrain Institute, CRM Bldg. Room 343
    New Orleans, LA 70148

    (504) 280-1030 (voice)
    (504) 280-4022 (FAX)

Why was the data set created?

To release data that was originally intended to be published in a paper atlas in a digital format.

To up-date the shoreline change analysis by McBride and others (1992) and Penland and others (1998) for the Isles Dernieres to 1996.

How was the data set created?

  1. From what previous works were the data drawn?

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

    (process 1 of 2)
    The projection was defined as UTM and converted to Geographic NAD 83.

    Person who carried out this activity:

    U.S. Geological Survey
    c/o Jamey M. Reid
    IT Specialist (Data Management)
    Woods Hole Field Center
    Woods Hole, MA 025453-1598

    (508) 548-8700 x 2204 (voice)
    (508) 457-2310 (FAX)

    (process 2 of 2)
    Metadata was created for the new shapefile.

    Person who carried out this activity:

    U.S. Geological Survey
    c/o Jamey M. Reid
    IT Specialist (Data Management)
    Woods Hole Field Center
    Woods Hole, MA 025453-1598

    (508) 457-2204 (voice)
    (508) 457-2310 (FAX)

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

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

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

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

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: None

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

    U.S. Geological Survey
    c/o S. Jeffress Williams
    Woods Hole Field Center
    Woods Hole, MA 02543-1598

    (508) 457-2383 (voice)
    (508) 457-2310 (FAX)

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

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    Although this data set has been used by the U.S. Geological Survey (USGS), no warranty, express or implied, is made by the USGS as to the accuracy of the data and/or related materials. 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.

  4. How can I download or order the data?

Who wrote the metadata?

Last modified: 25-Jul-2003

Metadata author:
U.S. Geological Survey
c/o Jamey M. Reid
IT Specialist (Data Management)
Woods Hole Field Center
Woods Hole, MA 025453-1598

(508) 548-8700 x 2204 (voice)
(508) 457-2310 (FAX)

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

Metadata extensions used:

Generated by mp version 2.7.3 on Wed Aug 06 09:23:46 2003