Long-Term Shoreline Change Rates for Texas Generated at a 50m Transect Spacing, 1850-2001

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Frequently-anticipated questions:

What does this data set describe?
    Title:
    Long-Term Shoreline Change Rates for Texas Generated at a 50m Transect Spacing, 1850-2001
    Abstract:
    Rates of long-term and short-term shoreline change were generated in a GIS with the Digital Shoreline Analysis System (DSAS) version 2.0, an ArcView extension developed by the USGS in cooperation with TPMC Environmental Services. The extension is designed to efficiently lead a user through the major steps of shoreline change analysis. This extension to ArcView contains three main components that define a baseline, generate orthogonal transects at a user-defined separation along the coast, and calculate rates of change (linear regression, endpoint rate, average of rates, average of endpoints, jackknife).

  1. How should this data set be cited?

    Morton, Robert, and Miller, Tara, 2004, Long-Term Shoreline Change Rates for Texas Generated at a 50m Transect Spacing, 1850-2001: Open-File Report 2004-1089, U.S. Geological Survey, Coastal and Marine Geology Program, U.S. Geological Survey, Center for Coastal and Watershed Studies, St. Petersburg, FL.

    Online Links:

    This is part of the following larger work.

    Morton, Robert, Miller, Tara, and Moore, Laura, 2004, National Assessment of Shoreline Change: Part 1, Historical Shoreline Changes and Associated Coastal Land Loss Along the U.S. Gulf of Mexico: Open-File Report 2004-1043, U.S. Geological Survey, Coastal and Marine Geology Program, U.S. Geological Survey, Center for Coastal and Watershed Studies.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -97.399265
    East_Bounding_Coordinate: -93.905885
    North_Bounding_Coordinate: 29.700235
    South_Bounding_Coordinate: 25.955955

  3. What does it look like?

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

    Calendar_Date: 2003
    Currentness_Reference: publication date

  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 (10640)

    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 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?

    tx_transects_lt

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    ID
    Transect feature number. (Source: DSAS)

    Range of values
    Minimum:1
    Maximum:2131

    BASELNID
    Baseline segment from which the transect is generated. (Source: DSAS)

    Range of values
    Minimum:1
    Maximum:9

    TIMESTMP
    Date and time the rate calculation was generated. (Source: DSAS)

    A date and time stamp that is automatically generated by DSAS.

    AUTOGEN
    Indicates whether the transect was autogenerated or manually generated. (Source: DSAS)

    ValueDefinition
    1Transect was automatically generated by DSAS.
    No value givenTransect was manually generated or edited by user.

    STARTX
    X starting position of the transect in UTM meters. (Source: DSAS)

    Range of values
    Minimum:207119
    Maximum:793334

    STARTY
    Y starting position of the transect in UTM meters. (Source: DSAS)

    Range of values
    Minimum:2872286
    Maximum:3282949

    ENDX
    X ending position of the transect in UTM meters. (Source: DSAS)

    Range of values
    Minimum:205937
    Maximum:792247

    ENDY
    Y ending position of the transect in UTM meters. (Source: DSAS)

    Range of values
    Minimum:2872093
    Maximum:3285965

    AZIMUTH
    The transect's horizontal angular distance from north. (Source: DSAS)

    Range of values
    Minimum:0
    Maximum:360

    POINTCNT
    Number of shoreline intersections in the rate calculation. (Source: DSAS)

    Range of values
    Minimum:4
    Maximum:4

    LRR
    Linear regression rate. (Source: DSAS)

    Range of values
    Minimum:-9.2
    Maximum:14.9
    Units:meters per year (m/yr)

    R2_LRR
    Correlation coefficient (r^2). (Source: DSAS)

    Range of values
    Minimum:0
    Maximum:1

    SE_LRR
    Standard error of the estimate. (Source: DSAS)

    Range of values
    Minimum:0.0
    Maximum:1074.6
    Units:meters (m)

    CI90_LRR
    Standard error of the slope at a 90% confidence level. (Source: DSAS)

    Range of values
    Minimum:0.0
    Maximum:78.3
    Units:meters per year (m/yr)

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?

    U.S. Geological Survey, Center for Coastal and Watershed Studies
    600 4th Street South
    St. Petersburg, FL 33701
    USA

    (727) 803-8747 (voice)
    (727) 803-2032 (FAX)

    Hours_of_Service: Monday through Friday, 8 a.m. to 5 p.m., Eastern Standard Time

Why was the data set created?
Historical shoreline change is considered to be a crucial element in studying the vulnerability of the national shoreline. These data are used in a shoreline change analysis for the USGS National Assessment Project.

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 1)
    A baseline was manually constructed seaward of, and parallel to, the trend of shorelines representing four general time periods (1800s, 1920s-1930s, 1970s, and 1998-2002). Using DSAS, transects were generated with a spacing of 50m and transect-shoreline intersection points were saved to a separate layer. Transects were manually eliminated to prevent calculation of rates in areas where less than four shorelines were intersected.

    Long-term rates of shoreline change, in units of m/yr, were calculated at each transect using linear regression applied to all four shoreline positions from the earliest (1800s) to the most recent (derived from lidar). Linear regression was selected because it has been shown to be the most statistically robust quantitative method when a limited number of shorelines are available and it is the most commonly applied statistical technique for expressing shoreline movement and estimating rates of change. Uncertainties for the long-term rates are also reported in units of m/yr and represent a 90% confidence interval for the slope of the regression line. This means with 90% statistical confidence that the true rate of shoreline change falls within the range defined by the reported value plus or minus the error value. The variability around the trend reflects both measurement and sampling errors. Short-term rates of shoreline change, in units of m/yr, were calculated using the endpoint method comparing the 1970s and most recent shoreline positions.

    Person who carried out this activity:

    U.S. Geological Survey, Center for Coastal and Watershed Studies
    600 4th Street South
    St. Petersburg, FL 33701
    USA

    (727) 803-8747 (voice)
    (727) 803-2032 (FAX)

    Hours_of_Service: Monday through Friday, 8 a.m. to 5 p.m., Eastern Standard Time
  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?

  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:
Public domain data from the U.S. government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information.

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

    U.S. Geological Survey, Center for Coastal and Watershed Studies
    600 4th Street South
    St. Petersburg, FL 33701
    USA

    (727) 803-8747 (voice)
    (727) 803-2032 (FAX)

    Hours_of_Service: Monday through Friday, 8 a.m. to 5 p.m., Eastern Standard Time
  2. What's the catalog number I need to order this data set?

    USGS Open-File Report 2004-1089

  3. What legal disclaimers am I supposed to read?

    Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, these data and information are provided with the understanding that they are not guaranteed to be usable, timely, accurate, or complete. Users are cautioned to consider carefully the provisional nature of these data and information before using them for decisions that concern personal or public safety or the conduct of business that involves substantial monetary or operational consequences. Conclusions drawn from, or actions undertaken on the basis of, such data and information are the sole responsibility of the user.

    Neither the U.S. Government nor any agency thereof, 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 data, software, information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights.

    Trade, firm, or product names and other references to non-USGS products and services are provided for information only and do not constitute endorsement or warranty, express or implied, by the USGS, USDOI, or U.S. Government, as to their suitability, content, usefulness, functioning, completeness, or accuracy.

  4. How can I download or order the data?

Who wrote the metadata?
Dates:
Last modified: 06-Apr-2004

Metadata author:
U.S. Geological Survey, Center for Coastal and Watershed Studies
c/o Tara Miller
600 4th Street South
St. Petersburg, FL 33701
USA

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

Hours_of_Service: Monday through Friday, 8 a.m. to 5 p.m., Eastern Standard Time
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

Metadata extensions used:

Generated by mp version 2.7.33 on Tue Apr 06 14:21:00 2004