Shorelines for the Long Island Sound coastal region used in shoreline change analysis: Connecticut (1883-2016) and New York (1931-2014)

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Frequently anticipated questions:

What does this data set describe?

Title:
Shorelines for the Long Island Sound coastal region used in shoreline change analysis: Connecticut (1883-2016) and New York (1931-2014)
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 informaitoin 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. 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.
Supplemental_Information:
Cross-referenced citations are applicable to the dataset as a whole. Additional citations are located within individual process steps that pertain specifically to the method described in that step.
  1. How might this data set be cited?
    Henderson, Rachel E., Kratzmann, Meredith G., and Farris, Amy S., 20250922, Shorelines for the Long Island Sound coastal region used in shoreline change analysis: Connecticut (1883-2016) and New York (1931-2014): 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: -73.817423
    East_Bounding_Coordinate: -71.852907
    North_Bounding_Coordinate: 41.343788
    South_Bounding_Coordinate: 40.787171
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/67bfb060d34e8876fcbfc9c9?name=LIS_shorelines.jpg&allowOpen=true (JPEG)
    Map view of data, blue line indicates the linear extent of the shorelines.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date:
    Ending_Date: 2016
    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 (6081)
    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_84.
      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_shorelines
    Shorelines for coastal Long Island Sound used in shoreline change analysis. (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.
    OBJECTID
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Date_
    Date of shoreline position; date of survey as indicated on source material. A default date of 07/01 was assigned to shorelines where only the year was known (month and day unknown). Using July, the mid-point month of the calendar year, minimizes the potential offset to the actual shoreline date by a maximum of six months. (Source: U.S. Geological Survey) Date of the shoreline in mm/dd/yyyy
    Uncy
    Estimate of shoreline position uncertainty in meters. Actual shoreline position is within the range of this value (plus or minus, meters). The historic shoreline uncertainty values incorporate measurement uncertainties associated with mapping methods and materials for historical shorelines, the geographic registration of shoreline position, and shoreline digitizing. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.57
    Maximum:11.7
    Source
    Agency that provided shoreline feature or the data source used to digitize shoreline feature. (Source: U.S. Geological Survey) Name of the agency where shoreline data was aquired from. See lineage for all data source citations.
    Source_b
    Type of data used to create shoreline. (Source: U.S. Geological Survey)
    ValueDefinition
    Aerial PhotographyShoreline derived from Aerial Photography
    Lidar - contour methodShoreline derived from lidar data (contour extraction method)
    Lidar - profile methodShoreline derived from lidar data (profile extraction method)
    NOAA T-SheetShoreline derived from NOAA Topographic Survey Sheets (T-Sheet)
    Year_
    Four-digit year of shoreline (Source: U.S. Geological Survey)
    Range of values
    Minimum:1883
    Maximum:2016
    Default_D
    Differentiates between shorelines that have known month and day attributes and those that use the default value of 07/01 when only the year is known. (Source: U.S. Geological Survey)
    ValueDefinition
    0Shoreline month and day are known.
    1Shoreline month and day are unknown and default value of 07/01 was used.
    DSAS_type
    Shoreline type field used to specify the datum to which the shoreline is referenced. (Source: U.S. Geological Survey)
    ValueDefinition
    MHWMean High Water (datum-based shoreline).
    HWLHigh Water Line (proxy-based shoreline).
    STATE
    Abbreviation of the State that the shoreline data lie within. (Source: U.S. Geological Survey)
    ValueDefinition
    NYNew York
    CTConnecticut
    Contour
    Value of average MHW elevation (meters above NAVD88) that was used to extract the contour shoreline from DEM or point cloud data. The value is different based on the average MHW for different areas of Long Island Sound. A value of 9999 in the attribute table means the value is null, in this case 9999 values are present for shorelines not extracted with a MHW value (t-sheet and air photo sources). (Source: U.S. Geological Survey)
    ValueDefinition
    9999Null value
    Range of values
    Minimum:0.4
    Maximum:1.0
    SRCE_INFO
    Information regarding source data used to digitize shoreline feature. (Source: U.S. Geological Survey) Character string of length 50
    County
    County that the shoreline data lie within. (Source: U.S. Geological Survey) Character string of length 25
    Shape_Leng
    Length of shoreline in meter units (UTM zone 18N NAD 83). (Source: U.S. Geological Survey, Woods Hole Science Center)
    Range of values
    Minimum:0.006
    Maximum:15035.860
    Entity_and_Attribute_Overview:
    The entity and attribute information provided here describes the tabular data associated with the dataset. Please review the individual attribute descriptions for detailed information.
    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
    • Amy S. Farris
  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?

This dataset includes shoreline positions compiled from existing and new data sources for Long Island Sound (LIS) in New York and Connecticyt from the 1800s to the 2010s. Historical shorelines were compiled from a variety of sources including NOAA Topographic Survey Sheets (T-sheets), aerial photography, and lidar data. New York (NY): New York shorelines span 83 years ranging from 1931 to 2014. Shorelines were compiled from NOAA T-sheets, aerial photography (NOAA Continually Updated Shoreline Product (CUSP)), and lidar (USGS, NOAA, Capital Region Council of Governments (CRCOG), New York State Department of Environmental Conservation (NYSDEC), and U.S. Army Corps of Engineers (USACE)). Connecticut (CT): Connecticut shorelines span 133 years ranging from 1883 to 2016. Shorelines were compiled from topographic survey sheets (NOAA, University of Connecticut (UCONN)) and lidar (USGS, NOAA, UCONN, CRCOG, USACE, and the Federal Emergency Management Agency (FEMA)).
New York and Connecticut shoreline datasets were merged into one shapefile for Long Island Sound. Historical shoreline positions serve as easily understood features that can be used to describe the movement of beaches through time. Long-term (LT) and short-term (ST) shoreline change rates were generated using the Digital Shoreline Analysis System (DSAS) version 5.1. DSAS uses a measurement baseline method to calculate rate-of-change statistics. Transects are cast from the reference baseline to intersect each shoreline, establishing measurement points used to calculate shoreline change rates.

How was the data set created?

  1. From what previous works were the data drawn?
    T-sheet shorelines (source 1 of 12)
    National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Unknown, Scanned National Ocean Service (NOS) Coastal Survey Maps (also known as Topographic Survey sheets, or T-sheets): National Oceanic and Atmospheric Administration, Washington, D.C..

    Online Links:

    Other_Citation_Details:
    T-sheet and shoreline data from the 1930s to the 1980s were downloaded in 2023. NOAA 1800s-era T-sheets and shorelines were also downloaded but did not pass quality assurance standards and were not used in the analysis.
    Type_of_Source_Media: digital data
    Source_Contribution:
    T-sheets used for QA/QC of NOAA-digitized 1930s-1980s shorelines and/or used as data source to digitize shorelines.
    CT 1800s UCONN (source 2 of 12)
    O’Brien, Kevin, Stocker, Joel, Barrett, Juliana, and Hyde, Bruce, 2014, Analysis of Shoreline Change in Connecticut: University of Connecticut (UCONN), Storrs, CT.

    Online Links:

    Other_Citation_Details:
    Shorelines from the 1800s published by UCONN were included in the dataset for the state of CT only. The study was a cooperative effort between the Connecticut Department of Energy and Environmental Protection (DEEP), the Connecticut Sea Grant (CT Sea Grant), and the University of Connecticut Center for Land Use Education and Research (UCONN-CLEAR). The shorelines were obtained directly from the authors as the website links were broken at the time of request (March 2022).
    Type_of_Source_Media: digital data
    Source_Contribution: Shorelines for CT 1883-1887 included in the analysis.
    CT 2004 PTS (source 3 of 12)
    NOAA Office for Coastal Management (NOAA/OCM), 20060814, 2004 Connecticut Coastline Lidar Mapping: Office for Coastal Management, Charleston, SC.

    Online Links:

    Other_Citation_Details:
    Point cloud data were downloaded for the entire area of coverage from New Haven to Old Saybrook, CT. Downloaded 05/01/2024.
    Type_of_Source_Media: digital data
    Source_Contribution:
    The elevation data were downloaded as a point cloud (.laz) for extraction of datum-based shoreline (profile/contour).
    2004-2006 CUSP shorelines (source 4 of 12)
    National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Unknown, NOAA NGS Continually Updated Shoreline Product (CUSP): Office for Coastal Management, Charleston, SC.

    Online Links:

    Other_Citation_Details:
    CUSP (N40W075) shoreline for 09/06/2005 derived from aerial photography. Data downloaded 2024. Site accessed 9/15/2025.
    Type_of_Source_Media: digital data
    Source_Contribution:
    The NOAA CUSP shoreline was used to supplement locations where fewer than 3 shorelines were available for analysis. In areas where sufficient data (historical and lidar) were available, CUSP was not used.
    CT 2006 DEM (source 5 of 12)
    Federal Emergency Management Agency (FEMA) and NOAA Office for Coastal Management, 20130401, 2006 Federal Emergency Management Agency (FEMA) Topographic LiDAR: Connecticut Coastline Survey: Office for Coastal Management, Charleston, SC.

    Online Links:

    Other_Citation_Details:
    DEM data were downloaded for the entire area of coverage from Port Chester, NY to Pawcatuck, CT with a large data gap in the area of Old Saybrook, CT. Downloaded 2-meter DEM. Projection was NAD 1983 UTM Zone 18N referenced to the North American Vertical Datum of 1988 (NAVD88). Data accessed and downloaded 05/01/2024.
    Type_of_Source_Media: digital data
    Source_Contribution:
    The elevation data were downloaded as DEM tiles for extraction of datum-based shoreline (profile/contour).
    CT 2012 DEM (source 6 of 12)
    US Army Corps Of Engineers (USACE) and NOAA Office for Coastal Management, 20130101, 2012 USACE Post Sandy Topographic LiDAR: Coastal Connecticut: Office for Coastal Management, Charleston, SC.

    Online Links:

    Other_Citation_Details:
    DEM data were downloaded for the entire area of coverage from Port Chester, NY to Pawcatuck, CT. Downloaded 1-meter DEM. Projection was NAD 1983 UTM Zone 18N referenced to the North American Vertical Datum of 1988 (NAVD88). Data accessed and downloaded 05/01/2024. Dataset credit: USACE, St. Louis District.
    Type_of_Source_Media: digital data
    Source_Contribution:
    The elevation data were downloaded as DEM tiles for extraction of datum-based shoreline (profile/contour).
    CT 2016 PTS (source 7 of 12)
    Capital Region Council of Governments (CRCOG) and NOAA Office for Coastal Management, 20171020, 2016 CRCOG Lidar: Connecticut Statewide: Office for Coastal Management, Charleston, SC.

    Online Links:

    Other_Citation_Details:
    Point cloud data were downloaded for the entire area of coverage from Port Chester, NY to Pawcatuck, CT. Downloaded 05/01/2024.
    Type_of_Source_Media: digital data
    Source_Contribution:
    The elevation data were downloaded as a point cloud (.laz) for extraction of datum-based shoreline (profile/contour).
    CT-NY 2011 PTS (source 8 of 12)
    U.S. Geological Survey, 20130501, 2011 USGS Lidar: Northeast (NY to ME).

    Online Links:

    Other_Citation_Details:
    Point cloud data were downloaded for areas of New York from Oyster Bay to Kings Point, and for Connecticut from Port Chester to Stratford Point. Downloaded 05/01/2024.
    Type_of_Source_Media: digital data
    Source_Contribution:
    The elevation data were downloaded as a point cloud (.laz) for extraction of datum-based shoreline (profile/contour).
    NY 2012 PTS (source 9 of 12)
    Capital Region Council of Governments and NOAA Office for Coastal Management, 20121101, 2011 - 2012 New York State Department of Environmental Conservation (NYSDEC) Lidar: Coastal New York (Long Island and along the Hudson River): Office for Coastal Management, Charleston, SC.

    Online Links:

    Other_Citation_Details:
    Point cloud data were downloaded for Port Chester, NY to Pawcatuck, CT. (Coverage not downloaded includes other portions of Long Island, NY) Downloaded 05/01/2024. Data set credit: New York State Department of Environmental Conservation (NYSDEC)
    Type_of_Source_Media: digital data
    Source_Contribution:
    The elevation data were downloaded as a point cloud (.laz) for extraction of datum-based shoreline (profile/contour).
    NY EAST 2012 DEM (source 10 of 12)
    US Army Corps Of Engineers (USACE) and NOAA Office for Coastal Management, 20130501, 2012 USACE NCMP Lidar: Post-Sandy (NJ, NY): Office for Coastal Management, Charleston, SC.

    Online Links:

    Other_Citation_Details:
    DEM data were downloaded for the area of coverage from Port Chester, NY to Oyster Bay, NY. Downloaded 2-meter DEM. Projection was NAD 1983 UTM Zone 18N referenced to the North American Vertical Datum of 1988 (NAVD88). Data set credit: US Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of Expertise (JALBTCX). Data downloaded 5/2024. Site accessed 9/15/2025.
    Type_of_Source_Media: digital data
    Source_Contribution:
    The elevation data were downloaded as DEM tiles for extraction of datum-based shoreline (profile/contour).
    NY WEST 2012 DEM (source 11 of 12)
    US Army Corps Of Engineers (USACE) and NOAA Office for Coastal Management, 20130501, 2012 USACE NCMP Post-Sandy Topobathy Lidar: Long Island, NY: Office for Coastal Management, Charleston, SC.

    Online Links:

    Other_Citation_Details:
    DEM data were downloaded for portions of Long Island near Mattituck and Orient Point, NY. Downloaded 1-meter DEM. Projection was NAD 1983 UTM Zone 18N referenced to the North American Vertical Datum of 1988 (NAVD88). Data set credit: US Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of Expertise (JALBTCX). Data downloaded 5/2024. Site accessed 9/15/2025.
    Type_of_Source_Media: digital data
    Source_Contribution:
    The elevation data were downloaded as DEM tiles for extraction of datum-based shoreline (profile/contour).
    NY 2014 PTS (source 12 of 12)
    US Army Corps Of Engineers (USACE) and NOAA Office for Coastal Management, 20130501, 2014 USGS CMGP Lidar: Post Sandy (Long Island, NY): Office for Coastal Management, Charleston, SC.

    Online Links:

    Other_Citation_Details:
    Point cloud data were downloaded for Port Washington, NY to Orient Point, NY. (Coverage not downloaded includes other portions of Long Island, NY) Downloaded 05/01/2024.
    Type_of_Source_Media: digital data
    Source_Contribution:
    The elevation data were downloaded as a point cloud (.laz) for extraction of datum-based shoreline (profile/contour).
  2. How were the data generated, processed, and modified?
    Date: 2023 (process 1 of 14)
    Historical shoreline data for Long Island Sound were downloaded from NOAA along with corresponding T-sheets for quality checking and editing the digitized shorelines. Shoreline data from T-sheets are proxy-based shorelines that represent the high-water line (HWL) at the time of survey. T-sheet shorelines were downloaded from the NOAA Shoreline Data Explorer at: https://nsde.ngs.noaa.gov/# 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)
    mkratzmann@contractor.usgs.gov
    Data sources used in this process:
    • T-sheet shorelines
    Data sources produced in this process:
    • USGS T-sheet shorelines
    Date: 2023 (process 2 of 14)
    Overview of the methods used to extract shoreline features from lidar data for Long Island Sound (CT and NY): In this data release, two methods of shoreline extraction from lidar were used: the contour method and the profile method. Both methods use the Mean High Water (MHW) elevation for shoreline extraction. The contour method was the primary method in the shoreline extraction process. Described in Farris and others (2018), the contour method extracts the elevation of average MHW value from DEM data using the ArcGIS Pro tool Contour List with the MHW value chosen for the contour. Also described in Farris and others (2018), the profile method produces a datum-based mean high water (MHW) shoreline. The profile method extracts the MHW shoreline point from the lidar point cloud data, using a cross shore transect in a MATLAB-based approach. These shorelines are polyline shapefiles that may be referred to as "profile shorelines" or "contour shorelines" in this metadata document to distinguish extraction methods, but note they are both lidar-derived. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Rachel E. Henderson
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    rehenderson@usgs.gov
    Date: 2023 (process 3 of 14)
    The MHW values for Long Island Sound were calculated using NOAA’s VDatum tool (version 4.1.2; https://vdatum.noaa.gov/) to model the regional surface using local MHW values based on the NAVD88 vertical datum. The MHW value ranges in Long Island Sound from 0.25 m to 1.15 m NAVD88 increasing in range from east to west. To keep the regionally averaged MHW value within 0.15 m of the actual MHW value, the area of Long Island Sound needed to be divided into different MHW zones. The following values were used calculate an average MHW for each described zone. All values are meters above NAVD88: Westerly, RI to Old Saybrook, CT average MHW used = 0.4 Old Saybrook, CT to New Haven, CT average MHW used = 0.7 New Haven, CT to Rye, NY average MHW used = 1.0 White Plains, NY to Port Jefferson Harbor, NY average MHW used = 1.0 Port Jefferson Harbor, NY to Mattituck Inlet, NY average MHW used = 0.88 Mattituck Inlet, NY to Orient Point, NY average MHW used = 0.62 Person who carried out this activity:
    U.S. Geological Survey
    Attn: Amy S. Farris
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    afarris@usgs.gov
    Date: 2023 (process 4 of 14)
    The following information applies to shorelines extracted using the profile method (Farris and others, 2018), as indicated in the “Source” attribute of the final dataset and includes the years 2016 (CT), 2014 (NY), 2012 (CT). The profile method used to extract the operational MHW shoreline from the lidar point cloud data utilizing the MATLAB-based approach (MATLAB version 2019b) is described in Farris and others (2018). The profile method used a coast-following reference line with 20-meter spaced profiles. All lidar data points that were within 1 meter of each profile line were associated with that profile. All processing was done on the 2-meter-wide profiles, working on a single profile at a time. For each profile, a linear regression was fit through data points on the foreshore and the regression was evaluated at the MHW elevation to yield the cross-shore position of the MHW shoreline. If there was a data gap at MHW or if the MHW elevation was obscured by water points, the linear regression was simply extrapolated to the MHW elevation. For each profile, the foreshore beach slope was defined as the slope of the regression line. This slope information is combined for all surveys and used to calculate uncertainty for profile- and contour-derived shorelines. Each MHW shoreline point that was extracted using this profile method has an uncertainty associated with it. This uncertainty includes four components: 1) the 95% confidence interval on the linear regression estimate of the shoreline position; 2) the vertical error of the raw lidar data as reported in the metadata; 3) a 15 cm vertical error in our chosen value of MHW, and; 4) the uncertainty due to extrapolation (if the shoreline was determined using extrapolation). These four components of uncertainty were added in quadrature to yield a total error for each shoreline point. See the shoreline attribute UNCY for individual values. Additional datasets were extracted using this method (CT 2012 PTS, NY 2014 PTS) and the slope information was used for uncertainty calculations. However, in further processing (see process step to combine profile and contour shorelines), the contour shorelines were found to have better coverage and were used for the final dataset. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Amy S. Farris
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    afarris@usgs.gov
    Data sources used in this process:
    • CT 2012 PTS
    • CT 2016 PTS
    • NY 2014 PTS
    Data sources produced in this process:
    • CT 2012 profile shoreline
    • CT 2016 profile shoreline
    • NY 2014 profile shoreline
    Date: 2024 (process 5 of 14)
    The following information applies to the shorelines extracted using the contour method (Farris and others, 2018) as indicated in the “Source” attribute of the final dataset and includes the years 2016 (CT), 2014 (NY), 2012 (CT, NY), 2011 (CT, NY), 2010 (CT), 2006 (CT). In some cases shorelines were extracted using both the profile and contour methods, and were combined in later processing. The following two steps outline the process for extraction using the contour method to extract the operational MHW shoreline from 1) the lidar point cloud (.laz) and 2) digital elevation model (raster .tif) datasets.
    This and the following steps were performed by the same person: Rachel E. Henderson Person who carried out this activity:
    U.S. Geological Survey
    Attn: Rachel E. Henderson
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 (voice)
    508-457-2310 (FAX)
    rehenderson@usgs.gov
    Date: 2024 (process 6 of 14)
    For contours extracted from point cloud data the following method was used: 1) Organized .laz files into groups based on the MHW value defined for the region (see MHW values for Long Island Sound). 2) Extracted point cloud data: The ArcGIS Pro tool “Convert LAS” was used to batch convert compressed lidar point cloud data (.laz) to a LAS dataset (LASD) dataset. In some cases, conversion to a LASD was a separate step, using the ArcGIS Pro tool “Create LAS Dataset.” a. Right-clicked on “Convert LAS” in tool list and selected “Batch” b. Chose batch parameter as “Input LAS” and accepted default to “make temporary batch tool” then clicked Next c. Batch input – navigated to and selected all .laz files d. Target folder set to save .las files e. File version: same as input f. Point format: (left blank) g. LAS options – unchecked “rearrange points” h. Output LAS Dataset: Created a new file name combining all the extracted LAS files into ONE dataset. i. Once created, verified that all the correct tiles were present (compared to index). Sometimes, individual LAS datasets were added using the LAS Dataset Layer > Data > “Add file” 3) Converted files from GCS to UTM: Used ArcGIS Pro tool “Extract LAS” specifying in “environments” to save the output to the correct UTM zone (18N). Output saved to a new LASD. 4) Created contours: ArcGIS Pro tool “Surface Contour.” a. Output Feature Class: navigated to target folder to save contours b. Contour interval: 100 c. Base contour: the value of MHW to be extracted (see MHW values for Long Island Sound) d. Contour Field: contour (default) e. Contour field precision: 2 f. Index interval: blank or divisible by contour interval: 200 g. Index Interval field: default h. Z factor: 1 Data sources used in this process:
    • CT 2004 PTS
    • CT 2016 PTS
    • CT-NY 2011 PTS
    • NY 2012 PTS
    • NY 2014 PTS
    Data sources produced in this process:
    • CT 2004 contour shoreline
    • CT 2016 contour shoreline
    • CT-NY 2011 contour
    • NY 2012 contour shoreline
    • NY 2014 contour shoreline
    Date: 2024 (process 7 of 14)
    For contours extracted from DEM data the following method was used: 1) Organized tiles into MHW zones (see process step describing MHW values for Long Island Sound). 2) Create contours: ArcGIS Pro tool “Contour List” a. Right clicked on “Contour List” in tool list and selected “Batch” b. Chose batch parameter as “Input LAS” and accepted default to “make temporary batch tool” then clicked Next c. Selected multiple rasters in the same MHW area d. Entered an output name e. Entered the MHW value for the region (see process step MHW values for Long Island Sound) Data sources used in this process:
    • CT 2006 DEM
    • CT 2012 DEM
    • NY EAST 2012 DEM
    • NY WEST 2012 DEM
    Data sources produced in this process:
    • CT 2006 contour shoreline
    • CT 2012 contour shoreline
    • NY EAST 2012 contour shoreline
    • NY WEST 2012 contour shoreline
    Date: 2024 (process 8 of 14)
    Lidar contour shorelines were smoothed using ArcGIS Pro tool “Smooth Line” and the “PAEK” (Polynomial Approximation with Exponential Kernel) smoothing algorithm. Smoothing tolerance = 10.
    Date: 2024 (process 9 of 14)
    The lidar shoreline shapefiles (profile and contour) were then visually checked against the imagery base map within ArcGIS Pro v3.5.57366 to make sure the shoreline was not interpolated through a headland or structure, for example. If issues were discovered, the shoreline was edited using standard Arc Tools to clip the feature. Attribute fields based on DSAS requirements, as well as source and publication information, were added to the attribute table and populated with the relevant information.
    Date: 2024 (process 10 of 14)
    The lidar shoreline shapefiles (profile and contour) were combined into one shapefile for evaluation. Where profile and contour shorelines of the same year had duplicate coverage, a decision was made to either use non-overlapping shoreline segments from both or choose a shoreline that was entirely extracted from either method. For example, profile and contour shorelines were extracted for CT 2016 and a decision was made to use a combination of profile- and contour-extracted shorelines. The “Source” attribute of the shorelines file shows which method was used to extract each segment. Data sources used in this process:
    • CT 2016 profile shoreline
    • CT 2016 contour shoreline
    • CT 2012 profile shoreline
    • CT 2012 contour shoreline
    • CT 2006 contour shoreline
    • CT 2004 contour shoreline
    • CT-NY 2011 contour shoreline
    • NY 2014 profile shoreline
    • NY 2014 contour shoreline
    • NY 2012 contour shoreline
    • NY WEST 2012 contour shoreline
    • NY EAST 2012 contour shoreline
    Data sources produced in this process:
    • LIS lidar shorelines
    Date: 2025 (process 11 of 14)
    Historical (1880s-1980s) were merged with the modern shorelines (2000s-2010s) in ArcGIS Pro v3.5.57366 to produce a single shorelines file for the Long Island Sound. Data sources used in this process:
    • USGS T-sheet shorelines
    • 2004-2006 CUSP shorelines
    • LIS lidar shorelines
    Data sources produced in this process:
    • LIS shorelines
    Date: 2025 (process 12 of 14)
    The shorelines shapefile (LIS_shorelines.shp) was imported into a personal geodatabase in ArcCatalog v10.9 by right-clicking on the geodatabase > Import for use with the Digital Shoreline Analysis System (DSAS) v5.1 software to perform rate calculations.
    Date: 2025 (process 13 of 14)
    The shorelines feature class was exported from a personal geodatabase to a shapefile in ArcCatalog v10.9 by performing a right-mouse click on the data layer > export > to shapefile (single).
    Date: 2025 (process 14 of 14)
    The shorelines shapefile was projected in ArcGIS Pro v3.5.57366 > Geoprocessing > Data Management Tools > Project. Parameters: input projection - UTM zone 18N NAD 83; 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.
    Ruggiero, Peter, and List, Jeffrey H., 200909, Improving Accuracy and Statistical Reliability of Shoreline Position and Change Rate Estimates: Journal of Coastal Research vol. 255, Coastal Education and Research Foundation, n/a.

    Online Links:

    Other_Citation_Details: pp. 1069-1081
    Farris, Amy S., Weber, Kathryn M., Doran, Kara S., and List, Jeffrey H., 2018, Comparing methods used by the U.S. Geological Survey Coastal and Marine Geology Program for deriving shoreline position from lidar data: Open-File Report 2018–1121, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    suggested citation: Farris, A.S., Weber, K.M., Doran, K.S., and List, J.H., 2018, Comparing methods used by the U.S. Geological Survey Coastal and Marine Geology Program for deriving shoreline position from lidar data: U.S. Geological Survey Open-File Report 2018–1121, 13 p., https://doi.org/10.3133/ofr20181121
    Weber, Kathryn M., List, Jeffrey H., and Morgan, Karen L.M., 2005, An operational mean high water datum for determination of shoreline position from topographic lidar data: Open-File Report 2005-1027, U.S. Geological Survey, Reston, VA.

    Online Links:

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

  1. How well have the observations been checked?
    The data provided here are a compilation of shorelines from multiple sources, spanning approximately 130 years. The attributes are based on the requirements of the Digital Shoreline Analysis System (DSAS) software and have gone through a series of quality assurance procedures.
  2. How accurate are the geographic locations?
    The horizontal accuracy of the shoreline data varies with respect to the data source from which the shorelines were digitized, the lidar data from which the shorelines were extracted, and the time period, and the method used to extract the shoreine data. T-sheet Shoreline Positional Uncertainty: Shorelines prior to 1960 (T-sheets) have an estimated positional uncertainty of plus or minus 10.8 meters (m). Shorelines from the 1960s-1980s (T-sheets) have an estimated positional uncertainty of plus or minus 5.1 m.
    Contour Shoreline Positional Uncertainty: We accounted for four sources of uncertainty in the contour method: 1) The vertical uncertainty of the lidar data (0.05 - 0.11 m) as found in the original lidar source metadata; 2) a mean high water (MHW) uncertainty of 0.15m to account for our simplified use an average MHW values for sections of Long Island Sound when in reality MHW continuously varies around Long Island Sound; 3) the horizontal uncertainty due to the cell size or point spacing of the DEM or point cloud (0.5 - 3.0 m) and 4) the horizontal uncertainty of the lidar data (0.3-1.0 m). Since the first two sources of uncertainty are vertical measurements, we converted both of them to a horizontal uncertainty using the beach slope. The beach slope was found by averaging all slope values calculated from the lidar profile shorelines (see process steps for a description). We divided both of the vertical uncertainty terms by the average beach slope (expressed as rise/run) in order to get the horizontal component of the two vertical uncertainty terms. In order to estimate the total horizontal uncertainty, the four, now horizontal, components of uncertainty were added in quadrature. These values are stored in the attribute tableas "Uncy". The average uncertainty, in meters, for the contour shorelines are as follows: CT 2004 = 3.2 m CT 2006 = 2.0 m CT 2012 = 1.6 m CT 2016 = 1.6 m NY-CT 2011 = 2.1 m NY 2012 = 2.1 m NY 2012 Post Sandy WEST = 2.2 m NY 2012 Post Sandy EAST = 1.8 m NY 2014 = 1.8 m Profile shoreline extraction was completed for three datasets (CT 2012, NY 2014 and, CT 2016). Not all profile shoreline segments were used for shoreline change analysis. In cases where coverage of contour shoreline and profile shoreline had overlapping coverage, only one shoreline was used for the final shoreline dataset. See shoreline attribute “Source_b” for determination of shoreline method used. Profile Shoreline Positional Uncertainty: We accounted for four sources of uncertainty in the profile method:: 1) the 95% confidence interval on the linear regression estimate of the shoreline position; 2) the uncertainty associated with the elevation of the raw lidar data and; 3) the uncertainty due to extrapolation. These three components of uncertainty were added in quadrature to yield a total error for each shoreline point. These errors were averaged for each profile shoreline segment (up to 2 kilometers). The range of uncertainty the profile shorelines used is 0.57 to 4.9 m, with an average of 2.17 m. See the data field UNCY for individual shoreline uncertainties.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This shoreline file is complete and contains all shoreline segments used to calculate shoreline change rates along sections of the Long Island Sound coastal region where shoreline position data were available. These data adequately represented the shoreline position at the time of the survey. Gaps in these data, if applicable, are a consequence of non-existing data or existing data that did not meet quality assurance standards. The digitized shoreline vectors downloaded from NOAA included attributes defining the shoreline type (see the entity attributes section of this metadata file under field name ATTRIBUTE). Other shoreline features (such as seawalls, bulkheads, jetties, upriver segments) were, for the most part, deleted. Some historically marsh-backed areas that were otherwise classified as sandy beach were preserved for this analysis. As this dataset represents an expansion of the National Shoreline Change effort into an area of highly variable geomorphology with significant areas of development, please take care when assessing the individual transect rates and measurements and consider the local geology/geomorphology in all cases.
  5. How consistent are the relationships among the observations, including topology?
    Adjacent shoreline segments do not overlap and are not necessarily continuous. Shorelines were quality checked for accuracy. Any slight offsets between adjacent segments due to georeferencing and digitizing error are taken into account in the uncertainty of the shoreline position, as reported in the horizontal accuracy section of this metadata file.

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. 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 polyline shorelines (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_shorelines_metadata.faq.html>
Generated by mp version 2.9.51 on Wed Sep 24 10:44:34 2025