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.
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.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
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.
Source_Information:
Source_Citation:
Citation_Information:
Originator:
National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS)
Publication_Date: Unknown
Title:
Scanned National Ocean Service (NOS) Coastal Survey Maps (also known as Topographic Survey sheets, or T-sheets)
Geospatial_Data_Presentation_Form: raster digital dataset
Publication_Information:
Publication_Place: Washington, D.C.
Publisher: National Oceanic and Atmospheric Administration
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.
Online_Linkage: https://nsde.ngs.noaa.gov/#
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1931
Ending_Date: 1984
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: T-sheet shorelines
Source_Contribution:
T-sheets used for QA/QC of NOAA-digitized 1930s-1980s shorelines and/or used as data source to digitize shorelines.
Source_Information:
Source_Citation:
Citation_Information:
Originator: Kevin O’Brien
Originator: Joel Stocker
Originator: Juliana Barrett
Originator: Bruce Hyde
Publication_Date: 2014
Title: Analysis of Shoreline Change in Connecticut
Geospatial_Data_Presentation_Form: vector digital dataset
Publication_Information:
Publication_Place: Storrs, CT
Publisher: University of Connecticut (UCONN)
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).
Online_Linkage: https://shorelinechange.uconn.edu/
Online_Linkage:
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1883
Ending_Date: 1887
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: CT 1800s UCONN
Source_Contribution: Shorelines for CT 1883-1887 included in the analysis.
Source_Information:
Source_Citation:
Citation_Information:
Originator: NOAA Office for Coastal Management (NOAA/OCM)
Publication_Date: 20060814
Title: 2004 Connecticut Coastline Lidar Mapping
Geospatial_Data_Presentation_Form: vector digital dataset
Publication_Information:
Publication_Place: Charleston, SC
Publisher: Office for Coastal Management
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.
Online_Linkage: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=20
Online_Linkage: https://www.fisheries.noaa.gov/inport/item/48168
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 20041008
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: CT 2004 PTS
Source_Contribution:
The elevation data were downloaded as a point cloud (.laz) for extraction of datum-based shoreline (profile/contour).
Source_Information:
Source_Citation:
Citation_Information:
Originator:
National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS)
Publication_Date: Unknown
Title: NOAA NGS Continually Updated Shoreline Product (CUSP)
Geospatial_Data_Presentation_Form: vector digital dataset
Publication_Information:
Publication_Place: Charleston, SC
Publisher: Office for Coastal Management
Other_Citation_Details:
CUSP (N40W075) shoreline for 09/06/2005 derived from aerial photography. Data downloaded 2024. Site accessed 9/15/2025.
Online_Linkage: https://nsde.ngs.noaa.gov/
Online_Linkage: https://inport.nmfs.noaa.gov/inport/item/60812
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 2004
Ending_Date: 2006
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: 2004-2006 CUSP shorelines
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.
Source_Information:
Source_Citation:
Citation_Information:
Originator:
Federal Emergency Management Agency (FEMA) and NOAA Office for Coastal Management
Publication_Date: 20130401
Title:
2006 Federal Emergency Management Agency (FEMA) Topographic LiDAR: Connecticut Coastline Survey
Geospatial_Data_Presentation_Form: raster digital dataset
Publication_Information:
Publication_Place: Charleston, SC
Publisher: Office for Coastal Management
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.
Online_Linkage: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=1468
Online_Linkage: https://www.fisheries.noaa.gov/inport/item/49654
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20061216
Ending_Date: 20061218
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: CT 2006 DEM
Source_Contribution:
The elevation data were downloaded as DEM tiles for extraction of datum-based shoreline (profile/contour).
Source_Information:
Source_Citation:
Citation_Information:
Originator:
US Army Corps Of Engineers (USACE) and NOAA Office for Coastal Management
Publication_Date: 20130101
Title: 2012 USACE Post Sandy Topographic LiDAR: Coastal Connecticut
Geospatial_Data_Presentation_Form: raster digital dataset
Publication_Information:
Publication_Place: Charleston, SC
Publisher: Office for Coastal Management
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.
Online_Linkage: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=1434
Online_Linkage: https://www.fisheries.noaa.gov/inport/item/49607
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20121114
Ending_Date: 20121116
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: CT 2012 DEM
Source_Contribution:
The elevation data were downloaded as DEM tiles for extraction of datum-based shoreline (profile/contour).
Source_Information:
Source_Citation:
Citation_Information:
Originator:
Capital Region Council of Governments (CRCOG) and NOAA Office for Coastal Management
Publication_Date: 20171020
Title: 2016 CRCOG Lidar: Connecticut Statewide
Geospatial_Data_Presentation_Form: vector digital dataset
Publication_Information:
Publication_Place: Charleston, SC
Publisher: Office for Coastal Management
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.
Online_Linkage:
Online_Linkage: https://www.fisheries.noaa.gov/inport/item/49615
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20160322
Ending_Date: 20160331
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: CT 2016 PTS
Source_Contribution:
The elevation data were downloaded as a point cloud (.laz) for extraction of datum-based shoreline (profile/contour).
Source_Information:
Source_Citation:
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20101211
Ending_Date: 20110325
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: CT-NY 2011 PTS
Source_Contribution:
The elevation data were downloaded as a point cloud (.laz) for extraction of datum-based shoreline (profile/contour).
Source_Information:
Source_Citation:
Citation_Information:
Originator:
Capital Region Council of Governments and NOAA Office for Coastal Management
Publication_Date: 20121101
Title:
2011 - 2012 New York State Department of Environmental Conservation (NYSDEC) Lidar: Coastal New York (Long Island and along the Hudson River)
Geospatial_Data_Presentation_Form: vector digital dataset
Publication_Information:
Publication_Place: Charleston, SC
Publisher: Office for Coastal Management
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)
Online_Linkage: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=1408
Online_Linkage: https://www.fisheries.noaa.gov/inport/item/49888
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20111126
Ending_Date: 20120407
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: NY 2012 PTS
Source_Contribution:
The elevation data were downloaded as a point cloud (.laz) for extraction of datum-based shoreline (profile/contour).
Source_Information:
Source_Citation:
Citation_Information:
Originator:
US Army Corps Of Engineers (USACE) and NOAA Office for Coastal Management
Publication_Date: 20130501
Title: 2012 USACE NCMP Lidar: Post-Sandy (NJ, NY)
Geospatial_Data_Presentation_Form: raster digital dataset
Publication_Information:
Publication_Place: Charleston, SC
Publisher: Office for Coastal Management
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.
Online_Linkage: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=2478
Online_Linkage: https://www.fisheries.noaa.gov/inport/item/50096
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 20121116
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: NY EAST 2012 DEM
Source_Contribution:
The elevation data were downloaded as DEM tiles for extraction of datum-based shoreline (profile/contour).
Source_Information:
Source_Citation:
Citation_Information:
Originator:
US Army Corps Of Engineers (USACE) and NOAA Office for Coastal Management
Publication_Date: 20130501
Title: 2012 USACE NCMP Post-Sandy Topobathy Lidar: Long Island, NY
Geospatial_Data_Presentation_Form: raster digital dataset
Publication_Information:
Publication_Place: Charleston, SC
Publisher: Office for Coastal Management
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.
Online_Linkage: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=9427
Online_Linkage: https://www.fisheries.noaa.gov/inport/item/49608
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20121114
Ending_Date: 20121115
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: NY WEST 2012 DEM
Source_Contribution:
The elevation data were downloaded as DEM tiles for extraction of datum-based shoreline (profile/contour).
Source_Information:
Source_Citation:
Citation_Information:
Originator:
US Army Corps Of Engineers (USACE) and NOAA Office for Coastal Management
Publication_Date: 20130501
Title: 2014 USGS CMGP Lidar: Post Sandy (Long Island, NY)
Geospatial_Data_Presentation_Form: vector digital dataset
Publication_Information:
Publication_Place: Charleston, SC
Publisher: Office for Coastal Management
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.
Online_Linkage: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=4938
Online_Linkage: https://www.fisheries.noaa.gov/inport/item/49890
Type_of_Source_Media: digital data
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20121114
Ending_Date: 20121115
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: NY 2014 PTS
Source_Contribution:
The elevation data were downloaded as a point cloud (.laz) for extraction of datum-based shoreline (profile/contour).
Process_Step:
Process_Description:
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/#
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Meredith Kratzmann
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543
Contact_Voice_Telephone: 508-548-8700
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: mkratzmann@contractor.usgs.gov
Process_Step:
Process_Description:
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.
Process_Date: 2023
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Rachel E. Henderson
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543
Contact_Voice_Telephone: 508-548-8700
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: rehenderson@usgs.gov
Process_Step:
Process_Description:
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
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Amy S. Farris
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543
Contact_Voice_Telephone: 508-548-8700
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: afarris@usgs.gov
Process_Step:
Process_Description:
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.
Source_Used_Citation_Abbreviation: CT 2012 PTS
Source_Used_Citation_Abbreviation: CT 2016 PTS
Source_Used_Citation_Abbreviation: NY 2014 PTS
Process_Date: 2023
Source_Produced_Citation_Abbreviation: CT 2012 profile shoreline
Source_Produced_Citation_Abbreviation: CT 2016 profile shoreline
Source_Produced_Citation_Abbreviation: NY 2014 profile shoreline
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Amy S. Farris
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543
Contact_Voice_Telephone: 508-548-8700
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: afarris@usgs.gov
Process_Step:
Process_Description:
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
Process_Date: 2024
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Rachel E. Henderson
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543
Contact_Voice_Telephone: 508-548-8700
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: rehenderson@usgs.gov
Process_Step:
Process_Description:
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
Source_Used_Citation_Abbreviation: CT 2004 PTS
Source_Used_Citation_Abbreviation: CT 2016 PTS
Source_Used_Citation_Abbreviation: CT-NY 2011 PTS
Source_Used_Citation_Abbreviation: NY 2012 PTS
Source_Used_Citation_Abbreviation: NY 2014 PTS
Process_Date: 2024
Source_Produced_Citation_Abbreviation: CT 2004 contour shoreline
Source_Produced_Citation_Abbreviation: CT 2016 contour shoreline
Source_Produced_Citation_Abbreviation: CT-NY 2011 contour
Source_Produced_Citation_Abbreviation: NY 2012 contour shoreline
Source_Produced_Citation_Abbreviation: NY 2014 contour shoreline
Process_Step:
Process_Description:
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)
Source_Used_Citation_Abbreviation: CT 2006 DEM
Source_Used_Citation_Abbreviation: CT 2012 DEM
Source_Used_Citation_Abbreviation: NY EAST 2012 DEM
Source_Used_Citation_Abbreviation: NY WEST 2012 DEM
Process_Date: 2024
Source_Produced_Citation_Abbreviation: CT 2006 contour shoreline
Source_Produced_Citation_Abbreviation: CT 2012 contour shoreline
Source_Produced_Citation_Abbreviation: NY EAST 2012 contour shoreline
Source_Produced_Citation_Abbreviation: NY WEST 2012 contour shoreline
Process_Step:
Process_Description:
Lidar contour shorelines were smoothed using ArcGIS Pro tool “Smooth Line” and the “PAEK” (Polynomial Approximation with Exponential Kernel) smoothing algorithm. Smoothing tolerance = 10.
Process_Date: 2024
Process_Step:
Process_Description:
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.
Process_Date: 2024
Process_Step:
Process_Description:
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.
Source_Used_Citation_Abbreviation: CT 2016 profile shoreline
Source_Used_Citation_Abbreviation: CT 2016 contour shoreline
Source_Used_Citation_Abbreviation: CT 2012 profile shoreline
Source_Used_Citation_Abbreviation: CT 2012 contour shoreline
Source_Used_Citation_Abbreviation: CT 2006 contour shoreline
Source_Used_Citation_Abbreviation: CT 2004 contour shoreline
Source_Used_Citation_Abbreviation: CT-NY 2011 contour shoreline
Source_Used_Citation_Abbreviation: NY 2014 profile shoreline
Source_Used_Citation_Abbreviation: NY 2014 contour shoreline
Source_Used_Citation_Abbreviation: NY 2012 contour shoreline
Source_Used_Citation_Abbreviation: NY WEST 2012 contour shoreline
Source_Used_Citation_Abbreviation: NY EAST 2012 contour shoreline
Process_Date: 2024
Source_Produced_Citation_Abbreviation: LIS lidar shorelines
Process_Step:
Process_Description:
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.
Source_Used_Citation_Abbreviation: USGS T-sheet shorelines
Source_Used_Citation_Abbreviation: 2004-2006 CUSP shorelines
Source_Used_Citation_Abbreviation: LIS lidar shorelines
Process_Date: 2025
Source_Produced_Citation_Abbreviation: LIS shorelines
Process_Step:
Process_Description:
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.
Process_Date: 2025
Process_Step:
Process_Description:
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).
Process_Date: 2025
Process_Step:
Process_Description:
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.
Process_Date: 2025
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Meredith G. Kratzmann
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing and physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Country: USA
Contact_Voice_Telephone: 508-548-8700
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: mkratzmann@contractor.usgs.gov
