Alabama: transects with long-term (LT) shoreline change rate calculations

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Frequently anticipated questions:

What does this data set describe?

Title:
Alabama: transects with long-term (LT) shoreline change rate calculations
Abstract:
The U.S. Geological Survey (USGS) maintains shoreline positions for the United States coasts from various historical sources, such as aerial photographs or topographic surveys, and contemporary sources, such as lidar-point clouds and digital elevation models. Shorelines are compiled in a Geographic Information System (GIS) and analyzed in the USGS Digital Shoreline Analysis System (DSAS) software to calculate rates of change. Keeping a record of historical shoreline positions is an effective method to monitor change over time, enabling scientists to identify areas most susceptible to erosion or accretion. These data can help coastal managers understand which areas of the coast are vulnerable to change. The shoreline positions and shoreline change rates provide actionable information to homeowners, coastal communities, and managers of public and private properties to improve resiliency for coastal hazards.
  1. How might this data set be cited?
    Kratzmann, Meredith G., 20260622, Alabama: transects with long-term (LT) shoreline change rate calculations: data release DOI:10.5066/P1JE2KSO, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Kratzmann, Meredith G., Farris, Amy S., and Weber, Kathryn M., 2026, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2020s for the coast of Alabama: data release DOI:10.5066/P1JE2KSO, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    suggested citation: Kratzmann, M.G., Farris, A.S., and Weber, K.M., 2026, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2020s for the coast of Alabama: U.S. Geological Survey data release, https://doi.org/10.5066/P1JE2KSO.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -88.335542
    East_Bounding_Coordinate: -87.518227
    North_Bounding_Coordinate: 30.291621
    South_Bounding_Coordinate: 30.218328
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/69e2b046b66b0195694c11e9?name=AL_rates_LT.png&allowOpen=true (PNG)
    Map view of data. Green lines indicate the extent of the long-term (century-scale) shoreline change rates for Alabama.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2026
    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 (1510)
    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 0.0000001. Longitudes are given to the nearest 0.0000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257224.
  7. How does the data set describe geographic features?
    AL_rates_LT.shp
    Transects and shorelines were used to generate intersection points and shoreline change rate transects. These attributes are for long-term rates in Alabama. (Source: U.S. Geological Survey)
    FID
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: Esri) Feature type.
    baselineid
    Unique identification number of the baseline segment starting at 1. If baselineid= 0 no transects will be generated. Used by DSAS to determine transect ordering alongshore if multiple baseline segments exist. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:4
    transorder
    Number assigned by DSAS based on the ordering of transects from baseline start to baseline end. (Source: U.S. Geological Survey)
    Range of values
    Minimum:37
    Maximum:1819
    length
    Length of feature in meter units. (Source: Esri)
    Range of values
    Minimum:489.76
    Maximum:1593.94
    Units:meters
    tcd
    The total cumulative distance (TCD) is the measure in meters alongshore from the start of the baseline segment with an identifier of 1 and measured sequentially alongshore to the end of the final baseline segment. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1800
    Maximum:90900
    Units:meters
    shrcount
    Number of shorelines used to compute shoreline change metrics. (Source: U.S. Geological Survey)
    Range of values
    Minimum:5
    Maximum:32
    lrr
    A linear regression rate-of-change statistic was calculated by fitting a least-squares regression line to all shoreline points for a particular transect, using shoreline position plotted against shoreline date. Any shoreline points that are referenced to HWL were adjusted by the proxy-datum bias distance (meters) along the transect to correct for the offset between proxy-based HWL and datum-based MHW shorelines. The best-fit regression line is placed so that the sum of the squared residuals (determined by squaring the offset distance of each data point from the regression line and adding the squared residuals together) is minimized. The linear regression rate is the slope of the line. The rate is reported in meters per year with positive values indicating accretion (shoreline advance, seaward movement) and negative values indicating erosion (shoreline retreat, landward movement). (Source: U.S. Geological Survey)
    Range of values
    Minimum:-4.15
    Maximum:10.05
    Units:meters per year
    lr2
    The R-squared statistic, or coefficient of determination, is the proportion of variance in the data that is explained by a regression. It is a dimensionless index that ranges from 1.0 to 0.0 and measures how successfully the best-fit line accounts for variation in the data. The smaller the variability of the residual values around the regression line relative to the overall variability, the better the prediction (and closer the R-squared value is to 1.0). (Source: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:0.96
    lci90
    The standard error of the slope with confidence interval describes the uncertainty of the reported rate. The LRR rates are determined by a best-fit regression line for the shoreline data at each transect. The slope of this line is the reported rate of change (in meters/year). The confidence interval (LCI) is calculated by multiplying the standard error of the slope by the two-tailed test statistic at the user-specified 90 percent confidence. This value is often reported in conjunction with the slope to describe the confidence of the reported rate. For example: LRR = 1.2 LCI90 = 0.7 could be reported as a rate of 1.2 (+/-) 0.7 meters/year. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.06
    Maximum:3.15
    Units:meters
    lse
    This quantity is the standard error of the regression, also known as the standard error of the estimate. To calculate it, the distance between each data point and the regression line is calculated. These distances are squared then summed. The sum is divided by the number of data points minus two. The square root is taken of the result. (Source: U.S. Geological Survey)
    Range of values
    Minimum:6.26
    Maximum:404.83
    Units:meters
    epr
    The end point rate is calculated by dividing the distance of shoreline movement by the time elapsed between two shorelines, the oldest and most recent only. The rate is reported in meters per year with positive values indicating accretion (shoreline advance, seaward movement) and negative values indicating erosion (shoreline retreat, landward movement). (Source: U.S. Geological Survey)
    Range of values
    Minimum:-3.92
    Maximum:12.50
    Units:meters per year
    eprunc
    Describes the uncertainty of the reported end point rate (EPR) in meters. The shoreline uncertainties for the two positions used in the end point calculation are each squared then added together (summation of squares). The square root of the summation of squares is divided by the number of years between the two shorelines. This result is reported as the confidence of the end point rate calculation (eprunc). (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.06
    Maximum:0.36
    Units:meters
    nsm
    The net shoreline movement (NSM) is the distance in meters between the oldest and the most recent shorelines. (Source: U.S. Geological Survey)
    Range of values
    Minimum:-590.94
    Maximum:1067.54
    Units:meters
    sce
    The shoreline change envelope (SCE) value represents the greatest distance that covers all the shorelines intersected by a transect. The value for SCE is always positive, as the metric is based on magnitude, not direction. (Source: U.S. Geological Survey)
    Range of values
    Minimum:33.27
    Maximum:1171.93
    Units:meters
    nb_lrr
    A linear regression rate-of-change statistic as described in the attribute lrr but without the proxy-datum bias correction applied (nb= no bias applied). (Source: U.S. Geological Survey)
    Range of values
    Minimum:-4.12
    Maximum:10.09
    Units:meters per year
    nb_lr2
    The R-squared statistic, or coefficient of determination, as described in the attribute lr2 but for nb_ (no bias applied) rates. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:0.96
    nb_lci90
    The 90 percent confidence interval as described in the attribute lci90 but for nb_ (no bias applied) rates. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.07
    Maximum:3.15
    Units:meters
    nb_lse
    The standard error as described in the attribute LSE but for nb_ (no bias applied) rates. (Source: U.S. Geological Survey)
    Range of values
    Minimum:6.84
    Maximum:404.75
    Units:meters
    nb_epr
    The end point rate as described in the attribute epr but for nb_ (no bias applied) rates. (Source: U.S. Geological Survey)
    Range of values
    Minimum:-3.92
    Maximum:12.57
    Units:meters per year
    nb_eprunc
    The uncertainty of the end point rate (EPR) as described in the attribute epr but for nb_ (no bias applied) rates. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.06
    Maximum:0.36
    Units:meters
    nb_nsm
    The net shoreline movement (NSM) is the distance in meters between the oldest and the most recent shorelines (no bias applied). (Source: U.S. Geological Survey)
    Range of values
    Minimum:-586.45
    Maximum:1072.28
    Units:meters
    nb_sce
    The shoreline change envelope (SCE) value represents the greatest distance that covers all the shorelines intersected by a transect (no bias applied). (Source: U.S. Geological Survey)
    Range of values
    Minimum:30.11
    Maximum:1176.66
    Units:meters
    Entity_and_Attribute_Overview:
    The entity and attribute information provided here describes the tabular data associated with long-term shoreline change rates for Alabama. Please review the individual attribute descriptions for detailed information. All calculations for length are in meter units, NAD_1983_2011_UTM_Zone_16N.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Meredith G. Kratzmann
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Meredith G. Kratzmann
    384 Woods Hole Road
    Woods Hole, MA
    USA

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

Why was the data set created?

Shoreline positions were compiled for Alabama from the mid-1800s through the 2020s and were used to calculate long-term (century-scale) shoreline change rates using the Digital Shoreline Analysis System (DSAS) software developed by the U.S. Geological Survey. A reference baseline was used as the originating point for the orthogonal transects cast by the DSAS software. The transects intersect each shoreline, establishing measurement points which provide location and time information used to calculate rates of change. Rate calculations were computed using DSAS version 6.1.

How was the data set created?

  1. From what previous works were the data drawn?
    AL_baseline (source 1 of 3)
    Kratzmann, Meredith G., 2026, Alabama: baseline generated to calculate shoreline change rates in Kratzmann, M.G., Farris, A.S., and Weber, K.M., 2026, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2020s for the coast of Alabama: U.S. Geological Survey data release, https://doi.org/10.5066/P1JE2KSO: data release DOI:10.5066/P1JE2KSO, U.S. Geological Survey, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details:
    The first link is to the larger work, the second link is to the baseline dataset.
    Type_of_Source_Media: digital data
    Source_Contribution:
    Baseline segments for Alabama (part of this same data release https://doi.org/10.5066/P1JE2KSO) are used by DSAS to cast measurement transects.
    AL_shorelines (source 2 of 3)
    Kratzmann, Meredith G., and Farris, Amy S., 2026, Alabama: shorelines (1849-2022) used to calculate shoreline change rates in Kratzmann, M.G., Farris, A.S., and Weber, K.M., 2026, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2020s for the coast of Alabama: U.S. Geological Survey data release, https://doi.org/10.5066/P1JE2KSO: data release DOI:10.5066/P1JE2KSO, U.S. Geological Survey, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details:
    The first link is to the larger work, the second link is to the shorelines dataset.
    Type_of_Source_Media: digital data
    Source_Contribution:
    Shoreline data for Alabama (part of this same data release https://doi.org/10.5066/P1JE2KSO).
    AL_bias (source 3 of 3)
    Kratzmann, Meredith G., and Farris, Amy S., 2026, Alabama: bias feature containing proxy-datum bias information used in shoreline change rate calculations in Kratzmann, M.G., Farris, A.S., and Weber, K.M., 2026, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2020s for the coast of Alabama: U.S. Geological Survey data release, https://doi.org/10.5066/P1JE2KSO: data release DOI:10.5066/P1JE2KSO, U.S. Geological Survey, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details:
    The first link is to the larger work, the second link is to the bias feature dataset.
    Type_of_Source_Media: digital data
    Source_Contribution:
    Bias feature for Alabama (part of this same data release https://doi.org/10.5066/P1JE2KSO) used by DSAS to calculate rates that account for the offset between proxy-based HWL/WDL and datum-based MHW shorelines.
  2. How were the data generated, processed, and modified?
    Date: 2026 (process 1 of 5)
    Overview of the workflow used to calculate shoreline change rates and intersection points as part of the shoreline change analysis using DSAS v6.1: 1) Transects were generated at 50-meter spacing using a manually created baseline and shorelines compiled for Alabama (see source citations in the shorelines metadata file); 2) Manual edits to transects performed; 3) Transects and shorelines were used to generate intersection points and calculate rates of change. The following process steps describe these actions.
    For more details on the DSAS software, please visit: https://www.usgs.gov/centers/whcmsc/science/digital-shoreline-analysis-system-dsas
    This and the following process steps were performed by the same person: Meredith Kratzmann. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Meredith Kratzmann
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    Date: 2026 (process 2 of 5)
    DSAS v6.1 was used to create transect features using the baseline and shorelines shapefiles for Alabama. Input parameters: shoreline layer = Shorelines_AL, baseline layer= Baseline_AL, transect spacing= 50 meters, transect length= 1500 meters, smoothing distance= 2000 meters, clip transects to shoreline extent= unchecked. File produced= AL_transects_ALL. Some transects were manually edited for length, moved, or deleted in an edit session using standard editing tools in ArcGIS Pro 3.5.5. Edited transect shapefile was renamed= AL_transects. Data sources used in this process:
    • Baseline_AL
    • Shorelines_AL
    Data sources produced in this process:
    • AL_transects
    Date: 2026 (process 3 of 5)
    To calculate long-term (LT) shoreline change rates, Alabama shorelines from 1849 to 2022 were utilized with the DSAS-generated transects to create shoreline intersect points and perform rate calculations. Input parameters: shoreline layer= Shorelines_AL, transects layer= AL_transects, bias feature= AL_bias, date range= full range (all shorelines), shoreline intersection threshold= 2, calculate= EPR (end point rate), LRR (linear regression rate), NSM (net shoreline movement), SCE (shoreline change envelope), confidence interval=90%, create DSAS summary report= checked. Shapefiles produced= al_transects_intersect_20260114_141331, al_transects_rates_20260114_141331. Data sources used in this process:
    • Shorelines_AL
    • AL_transects
    • AL_bias
    Data sources produced in this process:
    • al_transects_intersect_20260114_141331
    • al_transects_rates_20260114_141331
    Date: 2026 (process 4 of 5)
    The rates were exported from DSAS in shapefile format using the Export Data tool and renamed= AL_rates_LT. Data sources used in this process:
    • al_transects_rates_20260114_141331
    Data sources produced in this process:
    • AL_rates_LT
    Date: 2026 (process 5 of 5)
    The rates shapefile was projected in ArcGIS Pro v3.5.5 > Geoprocessing > Data Management Tools > Projections and Transformations > Project. Parameters: Input Coordinate System - NAD_1983_2011_UTM_Zone_16N; Output Coordinate System - GCS_WGS_1984; transformation = WGS_1984_(ITRF08)_To_NAD_1983_2011.
  3. What similar or related data should the user be aware of?
    Henderson, Rachel E., Farris, Amy S., Kratzmann, Meredith G., Bartlett, Marie K., Ergul, Ayhan, McAndrews, John, Cibaj, Raison, Zichichi, Jessica L., Himmelstoss, Emily A., and Thieler, E. Robert, 2026, Digital Shoreline Analysis System version 6.1: software release version 6.1.177, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Use the first link to access the publication page. The second link is to the current version of DSAS (v6.1). The third link directs to the DSAS project page.

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

  1. How well have the observations been checked?
    The attributes of this dataset are based on the field requirements of the Digital Shoreline Analysis System and were automatically generated by the software during the generation of the transect layer or during the calculation of shoreline change rates.
  2. How accurate are the geographic locations?
    The uncertainty of the linear regression rate is estimated by the elements lr2, lse and lci90. See the attribute definition of each for more information.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This dataset contains the transects automatically generated by the DSAS software application that were used to calculate long-term (century-scale) shoreline change rates for the region. Additional transects may have been generated but did not meet the required number of shorelines or time period requirements.
  5. How consistent are the relationships among the observations, including topology?
    These data were generated using DSAS v6.1. The transects automatically generated by the software were visually inspected along with the shoreline data prior to rate calculations. Sometimes transect positions were manually edited to better represent an orthogonal position to the general trend of the shorelines.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints No access constraints. Please see 'Distribution Information' for details.
Use_Constraints These data are marked with a Creative Commons CC0 1.0 Universal License. These data are in the public domain and do not have any use constraints. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. These data were automatically generated using the DSAS v6.1 software application. 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. These data are not to be used for navigation.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Federal Center, Building 810, MS 302
    Denver, CO
    USA

    1-888-275-8747 (voice)
  2. What's the catalog number I need to order this data set? The dataset contains the polyline rates of shoreline change data, (SHP and other shapefile components), browse graphic, and the FGDC CSDGM metadata.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.
  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 a polyline shapefile format. The user must have software to read and process the data components of a shapefile.

Who wrote the metadata?

Dates:
Last modified: 22-Jun-2026
Metadata author:
Meredith G. Kratzmann
U.S. Geological Survey
384 Woods Hole Road
Woods Hole, MA
USA

508-548-8700 (voice)
508-457-2310 (FAX)
Contact_Instructions:
The metadata contact email address is a generic address in the event the person is no longer with USGS.
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P1JE2KSO/AL_rates_LT_metadata.faq.html>
Generated by mp version 2.9.51 on Mon Jun 22 16:21:27 2026