Shoreline change rates (long-term, 1800s-2010s) for the Long Island Sound coastal region using the Digital Shoreline Analysis System version 5.1

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Frequently anticipated questions:

What does this data set describe?

Title:
Shoreline change rates (long-term, 1800s-2010s) for the Long Island Sound coastal region using the Digital Shoreline Analysis System version 5.1
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 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. This data release, and other associated products, represents an expansion of the USGS national-scale shoreline database to include Long Island Sound (LIS) covering coastal areas in New York and Connecticut. 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 in Long Island Sound.
  1. How might this data set be cited?
    Henderson, Rachel E., and Kratzmann, Meredith G., 20250922, Shoreline change rates (long-term, 1800s-2010s) for the Long Island Sound coastal region using the Digital Shoreline Analysis System version 5.1: data release DOI:10.5066/P1TKEDFX, 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.

    Henderson, Rachel E., Kratzmann, Meredith G., Farris, Amy S., Lentz, Erika E., and Himmelstoss, Emily A., 2025, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2010s for the coast of Long Island Sound, New York and Connecticut: data release DOI:10.5066/P1TKEDFX, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    suggested citation: Henderson, R.E., Kratzmann, M.G., Farris, A.S., Lentz, E.E., and Himmelstoss, E.A., 2025, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2010s for the coast of Long Island Sound, New York and Connecticut: U.S. Geological Survey data release, https://doi.org/10.5066/P1TKEDFX
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -73.817326
    East_Bounding_Coordinate: -71.861386
    North_Bounding_Coordinate: 41.342565
    South_Bounding_Coordinate: 40.798362
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/67bfb0c1d34e8876fcbfc9ce?name=LIS_rates_LT.jpg&allowOpen=true (JPEG)
    Long Island Sound long-term shoreline change, yellow markers indicate data extent.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2025
    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 (6334)
    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?
    LIS_rates_LT.shp
    Transects were automatically generated by DSAS at a 90 degree angle to the user-specified baseline using a smoothing algorithm to maintain roughly parallel transects that are orthogonal with respect to the baseline. These attributes are for long-term rates in Long Island Sound (LIS). (Source: U.S. Geological Survey)
    FID
    Internal feature number used as a unique identifier of an object within a table primarily used in shapefiles. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: Esri) Feature type.
    TransectID
    A unique identification number for each transect. Values may not increment sequentially alongshore. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:6348
    BaselineID
    Unique identification number of the baseline segment. 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:64
    GroupID
    Optional field to aggregate transects on the basis of physical variations alongshore. The values, 1 (south coast) or 2 (north coast), were pulled from the baseline file Group_ID. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:2
    TransOrder
    Assigned by DSAS based on ordering of transects along the baseline. Used to allow user to sort transect data along the baseline from baseline start to baseline end. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1
    Maximum:6335
    Azimuth
    Assigned by DSAS to record the azimuth of the transect measure in degrees clockwise from North. If a transect position has been adjusted during the editing process, the azimuth value in the attribute table is updated automatically. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:360
    Units:degrees
    ShrCount
    Number of shorelines used to compute shoreline change metrics. (Source: U.S. Geological Survey)
    Range of values
    Minimum:2
    Maximum:8
    TCD
    The Total Cumulative Distance (TCD) is the measure in meters along shore from the start of the baseline segment with an ID=1 and measured sequentially alongshore to the end of the final baseline segment. (Source: U.S. Geological Survey)
    Range of values
    Minimum:200.04
    Maximum:483735.66
    Units:meters
    SCE
    The shoreline change envelope (SCE) reports a distance (in meters), not a rate. The SCE value represents the greatest distance among all the shorelines that intersect a given 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:0.08
    Maximum:300.02
    Units:meters
    NSM
    The net shoreline movement (NSM) is the distance between the oldest and the youngest shorelines for each transect, therefore, units are in meters. Positive values indicate accretion (seaward movement) and negative values indicate erosion (landward movement). . (Source: U.S. Geological Survey)
    Range of values
    Minimum:-300.02
    Maximum:262.31
    Units:meters per year
    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 (seaward movement) and negative values indicating erosion (landward movement). (Source: U.S. Geological Survey)
    Range of values
    Minimum:-6.25
    Maximum:3.35
    Units:meters per year
    EPRunc
    Describes the uncertainty of the reported end point rate 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:0.09
    Maximum:1.25
    Units:meters
    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. 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 (seaward movement) and negative values indicating erosion (landward movement). A LRR value of 9999 in the attribute table means that value is Null. This scenario occurs when ShrCount = 2 and there are not enough data points to calculate a linear regression rate. (Source: U.S. Geological Survey)
    ValueDefinition
    9999Null value
    Range of values
    Minimum:-2.47
    Maximum:3.33
    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). A LR2 value of 9999 in the attribute table means that LR2 is Null. This scenario occurs when ShrCount = 2 and there are not enough data points to calculate a linear regression rate. (Source: U.S. Geological Survey)
    ValueDefinition
    9999Null value
    Range of values
    Minimum:0
    Maximum:1
    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 point minus two. The square root is taken of the result. A LSE value of 9999 in the attribute table means that LSE is Null. This scenario occurs when ShrCount = 2 and there are not enough data points to calculate a linear regression rate. (Source: U.S. Geological Survey)
    ValueDefinition
    9999Null value
    Range of values
    Minimum:0
    Maximum:104.4
    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 (also called the standard deviation) 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. An LCI90 value of 9999 in the attribute table means that LCI90 is Null. This scenario occurs when ShrCount = 2 and there are not enough data points to calculate a linear regression rate. (Source: U.S. Geological Survey)
    ValueDefinition
    9999Null value
    Range of values
    Minimum:0
    Maximum:6.0
    SHAPE_Leng
    Length of feature in meter units (UTM zone 18N) (Source: Esri)
    Range of values
    Minimum:52.86836
    Maximum:276.991923
    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 Long Island Sound. Please review the individual attribute descriptions for detailed information. All calculations for length are in meter units and were based on the UTM zone 18N NAD83 projection.
    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)
    • Rachel E. Henderson
    • 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: Rachel E. Henderson
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    rehenderson@usgs.gov

Why was the data set created?

Shoreline positions were compiled for Long Island Sound from the late 1800s through 2010s and were used to calculate shoreline change rates using the Digital Shoreline Analysis System (DSAS) software developed by the U.S. Geological Survey. Long-term (NY: 83 years, CT: 133 years) shoreline change rates for the Long Island Sound coastal region are included in this dataset. 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 5.1.

How was the data set created?

  1. From what previous works were the data drawn?
    LIS_baseline (source 1 of 2)
    Henderson, Rachel E., and Kratzmann, Meredith G., 2025, Baseline for the Long Island Sound coastal region generated to calculate shoreline change rates using the Digital Shoreline Analysis System version 5.1 in Henderson, R.E., Kratzmann, M.G., Farris, A.S., Lentz, E.E., and Himmelstoss, E.A., 2025, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2010s for the coast of Long Island Sound, New York and Connecticut: U.S. Geological Survey data release, https://doi.org/10.5066/P1TKEDFX: data release DOI:10.5066/P1TKEDFX, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, 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 is to the baseline dataset.
    Type_of_Source_Media: digital data
    Source_Contribution:
    Baseline segments (part of this same data release https://doi.org/10.5066/P1TKEDFX) are used by DSAS to cast transects from which shoreline changes can be measured.
    LIS_shorelines (source 2 of 2)
    Henderson, Rachel E., and Kratzmann, Meredith G., 2025, Shorelines for the Long Island Sound coastal region used in shoreline change analysis: Connecticut (1883-2016) and New York (1931-2014) in Henderson, R.E., Kratzmann, M.G., Farris, A.S., Lentz, E.E., and Himmelstoss, E.A., 2025, National Shoreline Change—A GIS compilation of vector shorelines and associated shoreline change data from the 1800s to the 2010s for the coast of Long Island Sound, New York and Connecticut: U.S. Geological Survey data release, https://doi.org/10.5066/P1TKEDFX: data release DOI:10.5066/P1TKEDFX, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, 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 is to the shorelines dataset.
    Type_of_Source_Media: digital data
    Source_Contribution:
    Shoreline data for Long Island Sound (part of this same data release https://doi.org/10.5066/P1TKEDFX). Note the range of shoreline dates will vary by location.
  2. How were the data generated, processed, and modified?
    Date: 2025 (process 1 of 6)
    Overview of the workflow used to calculate shoreline change rates and intersection points as part of the Long Island Sound (LIS) shoreline change analysis using DSAS v5.1: 1) Transects were created at 50 meter spacing along shore using a manually created baseline, and shorelines compiled for Long Island Sound (see source citations); 2) Transect features and shorelines were used to generate shoreline intersection points and calculate rates of change; 3) Manual edits performed; 4) Data exported to shapefiles and; 5) Data updated to geographic WGS. Unless otherwise noted, process steps were performed by Rachel E. Henderson. Person who carried out this activity:
    Rachel E. Henderson
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    rehenderson@usgs.gov
    Date: 2025 (process 2 of 6)
    1) DSAS v5.1 was used to create interim transect features (stored in a personal geodatabase) to calculate long-term shoreline change rates. DSAS input parameters used: shoreline layer = LIS_Shorelines, baseline layer= LIS_Baseline, baseline group field=DSAS_group, transect spacing=50 meters, search distance=300 meters, shoreline intersection=seaward. File produced and saved to personal geodatabase = LIS_Trans_LT. Some transects were manually edited for length, moved, or deleted in an edit session using standard editing tools in ArcMap v10.8. For additional details on these parameters, please see the DSAS User Guide or visit the USGS website at: https://www.usgs.gov/centers/whcmsc/science/digital-shoreline-analysis-system-dsas. Data sources used in this process:
    • LIS_baseline
    • LIS_shorelines
    Data sources produced in this process:
    • LIS_Trans_LT
    Date: 2025 (process 3 of 6)
    2) To calculate long-term (LT) shoreline change rates, the entire range of shorelines from 1883 to 2016 were utilized with the DSAS-generated transects to create shoreline intersect points and shoreline change calculations stored as rate transects. Depending on the available data, the shorelines used for analysis may include those referenced to the datum-based mean high water (MHW), or a proxy-based feature such as the high water line (HWL). Input parameters used: shoreline layer= LIS_shorelines, shoreline date field=Date_, shoreline uncertainty field name=Uncy, the default accuracy=10 meters, shoreline intersection=seaward, transect layer= LIS_Trans_LT, stats calculations=all, shoreline threshold=0, confidence interval=90%. Files produced and saved to personal geodatabase = LIS_Trans_LT_rates, LIS_Trans_LT_intersects. Data sources used in this process:
    • LIS_shorelines
    • LIS_Trans_LT
    Data sources produced in this process:
    • LIS_Trans_LT_intersects
    • LIS_Trans_LT_rates
    Date: 2025 (process 4 of 6)
    3) Google Earth and other orthophoto mosaics were used to identify areas of rocky/bedrock coastlines and areas with significant anthropogenic modification. Rate transects and intersects in these areas were removed from the analysis using editing tools in ArcMap, while results in sandy areas were retained. Before exporting data, all null values were converted to the value 9999, as ArcGIS automatically changes Null values to zero values when converting from a feature class to a shapefile, which is problematic when presenting rates of change.
    Date: 2025 (process 5 of 6)
    4) The rate feature class was exported to a shapefile in ArcMap v10.8 by right-clicking the transect layer > data > export data. File renamed LIS_rates_LT. Data sources used in this process:
    • LIS_Trans_LT_rates
    Data sources produced in this process:
    • LIS_rates_LT
    Date: 2025 (process 6 of 6)
    5) The exported rate shapefile was projected in ArcGIS Pro v3.5.57366 > Geoprocessing > Data Management Tools > Project. Parameters: input projection - NAD83 UTM zone 18N ; output projection- geographic coordinates (WGS 84); transformation = WGS_1984_(ITRF00)_To_NAD_1983. Person who carried out this activity:
    Meredith G. Kratzmann
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    mkratzmann@contractor.usgs.gov
  3. What similar or related data should the user be aware of?
    Himmelstoss, Emily A., Farris, Amy S., Henderson, Rachel E., Kratzmann, Meredith G., Ergul, Ayhan, Zhang, Ouya, Zichichi, Jessica L., and Thieler, E. Robert, 2021, Digital Shoreline Analysis System (version 5.1): U.S. Geological Survey Software: software release version 5.1, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Use the first link to access the version of the software used (v5.1). The second link is to the current version of DSAS (v6.0). The third link directs to the DSAS project page.
    Himmelstoss, Emily A., Henderson, Rachel E., Kratzmann, Meredith G., and Farris, Amy S., 2021, Digital Shoreline Analysis System (version 5.1) User Guide: Open-File Report 2021-1091, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Use the first link to access the user guide. The second 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 performed by the software.
  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 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.#### add information about locations (such as Masons Island south of Mystic) where shoreline type was rocky/developed
  5. How consistent are the relationships among the observations, including topology?
    These data were generated using DSAS v5.1. 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 v5.1 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)
    sciencebase@usgs.gov
  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. The USGS or the U.S. Government shall not be held liable for improper or incorrect use of the data described and/or contained herein.
  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-Sep-2025
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)
whsc_data_contact@usgs.gov
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_P1TKEDFX/LIS_rates_LT_metadata.faq.html>
Generated by mp version 2.9.51 on Wed Sep 24 10:44:34 2025