Marsh Shorelines of the Massachusetts Coast from 2013-14 Topographic Lidar Data

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Frequently anticipated questions:

What does this data set describe?

Title:
Marsh Shorelines of the Massachusetts Coast from 2013-14 Topographic Lidar Data
Abstract:
The Massachusetts Office of Coastal Zone Management (CZM) launched the Shoreline Change Project in 1989 to identify erosion-prone areas of the Massachusetts coast. Seventy-six maps were produced in 1997 depicting a statistical analysis of shoreline change on ocean-facing shorelines from the mid-1800s to 1978 using multiple data sources. In 2001, a 1994 shoreline was added. More recently, in cooperation with CZM, the U.S. Geological Survey (USGS) delineated a new shoreline for Massachusetts using color aerial ortho-imagery from 2008 to 2009 and topographic lidar data collected in 2007. This update included a marsh shoreline, which was defined to be the tonal difference between low- and high-marsh seen in ortho-photos. Further cooperation between CZM and the U.S. Geological Survey (USGS) has resulted in another update in 2018, which includes beach shorelines, marsh shorelines and dune parameters, all of which were calculated from 2013-14 topographic lidar data. This metadata file describes the marsh shoreline that is part of the 2018 update. The marsh shoreline was defined to be the steep slope found at the seaward edge of the marsh vegetation. This definition was used because the marsh edge is the preferred shoreline indicator for computing rates of change and making position forecasts.
Supplemental_Information:
Note that the method may find an edge on any type of morphology (e.g. sandy beach or seawall). Therefore, the presence of a marsh edge does not necessarily mean that a marsh is present. In many parts of the state, a patchy marsh grass bed lies seaward of a sandy beach, this is called a fringing marsh. In these areas both the mean high water (MHW) shoreline and the marsh edge were kept because both have value. Since it was often difficult in imagery to distinguish sand, mud and brown marsh grass, and since we did not want to delete valid marsh sections, when in doubt, we kept the marsh edge even if it might not be on a marsh. To help elucidate this, an attribute named “MarshType” was added. It was set to “platform” if the marsh looked like a platform marsh. It was set to “fringing” if the marsh looked like a fringing marsh. It was set to “unknown” if it was not clear if the area was really a marsh. Note that all choices were subjective and based only on visual interpretation of the imagery.
  1. How might this data set be cited?
    Farris, Amy S., 2018, Marsh Shorelines of the Massachusetts Coast from 2013-14 Topographic Lidar Data: data release DOI:10.5066/F72R3QXR, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Farris, A.S., 2018, Marsh shorelines of the Massachusetts coast from 2013-14 topographic lidar data: U.S. Geological Survey data release, https://doi.org/10.5066/F72R3QXR.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -71.023
    East_Bounding_Coordinate: -69.932
    North_Bounding_Coordinate: 42.811
    South_Bounding_Coordinate: 41.2
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5aabdfafe4b081f61aaf00d5?name=MA_marsh_edge_browseGraphic.png (PNG)
    Image showing the mean tide level contour, calculated marsh edge, and a profile example of calculating the marsh edge.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 20-Nov-2013
    Ending_Date: 12-Apr-2014
    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 (447)
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.
  7. How does the data set describe geographic features?
    MA_marsh_edge_2013_2014.shp Attribute Table
    Table containing attribute information associated with the dataset. (Source: Producer defined)
    FID
    Internal feature number. (Source: ESRI) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: ESRI) Coordinates defining the features.
    Name
    name of feature (Source: Producer defined)
    ValueDefinition
    Marsh edgeMarsh edge determined by the maximum slope along a transect perpendicular to the mean tide level seaward of the mean high water line
    Date_
    date of the lidar data in the format MM/DD/YYYY (Source: Producer defined)
    ValueDefinition
    11/20/2013date of the lidar data
    04/07/2014date of the lidar data
    04/10/2014date of the lidar data
    04/04/2014date of the lidar data
    11/28/2013date of the lidar data
    12/04/2013date of the lidar data
    04/12/2014date of the lidar data
    MarshType
    type of marsh (Source: Producer defined)
    ValueDefinition
    platformMarsh looks like a platform marsh in NAIP imagery
    unknownThis particular spot might not be a marsh
    fringingMarsh looks like a fringing marsh in NAIP imagery
    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)
    • Amy S. Farris
  2. Who also contributed to the data set?
    Massachusetts Office of Coastal Zone Management
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Amy S. Farris
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2344 (voice)
    508-547-2310 (FAX)
    afarris@usgs.gov

Why was the data set created?

This 2013-2014 marsh shoreline is part of an update to the Massachusetts Office of Coastal Zone Management (CZM) Shoreline Change Project. It was extracted using a new slope-based method using topographic lidar data. The maximum slope was used to identify the edge of the marsh.

How was the data set created?

  1. From what previous works were the data drawn?
    2013-2014 Lidar data (source 1 of 3)
    United States Geological Survey (USGS), Coastal and Marine Geology Program (CMGP), National Aeronautics & Space Administration (NASA), and Department of Commerce (DOC), National Oceanic & Atmospheric Administration (NOAA), National Ocean Service (NOS), Office for Coastal Management (OCM), 20150710, 2013-2014 U.S. Geological Survey CMGP LiDAR: Post Sandy (MA, NH, RI): NOAA's Ocean Service, Office for Coastal Management (OCM), Charleston, SC.

    Online Links:

    Type_of_Source_Media: Digital imagery
    Source_Contribution:
    The topographic lidar data were used to create digital elevation models on which all the calculations were done.
    drone imagery (source 2 of 3)
    Sherwood, Christopher R, 2016, Low-altitude aerial imagery and related field observations associated with unmanned aerial systems (UAS) flights over Coast Guard Beach, Nauset Spit, Nauset Inlet, and Nauset Marsh, Cape Cod National Seashore, Eastham, Massachusetts on 1 March 2016: data release DOI:10.5066/F7CN721H, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: Digital imagery
    Source_Contribution:
    As mentioned in the “Attribute Accuracy” these data were used to validate results in a small area. This imagery is higher resolution and more accurate than what is available for the rest of the state. The marsh shoreline was plotted on this imagery to see how well the shoreline followed the marsh edge.
    NAIP imagery (source 3 of 3)
    Agency, Farm Service, 2014, National Agriculture Imagery Program.

    Online Links:

    Type_of_Source_Media: Digital imagery
    Source_Contribution:
    These data were used to validate results throughout the state. This imagery is more accurate than imagery provided by ArcGIS. The marsh shoreline was plotted on this imagery to see how well the shoreline followed the marsh edge.
  2. How were the data generated, processed, and modified?
    Date: 2017 (process 1 of 6)
    The mean tide level (MTL) for each marsh was found using VDatum (version 3.7). MTL varies from -0.08 to 0.08 m (above NAVD88) across the state. I used 0 m for all marshes. Mean High Water was determined for each marsh from Vdatum and Weber and others (2005). A single value was used for each marsh. Person who carried out this activity:
    Amy S. Farris
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2344 (voice)
    508-457-2310 (FAX)
    afarris@usgs.gov
    Data sources produced in this process:
    • MTL, MHW
    Date: 2017 (process 2 of 6)
    The processing steps outlined here were conducted for each marsh area separately. All marshes were chosen because there was a previous shoreline from the Massachusetts Shoreline Change Project update (Smith and others, 2013). Each marsh is geographically separated from the other marshes, so each was processed on its own. The goal of this first step is to get a mean tide level (MTL) contour to use as a baseline in the next step. The topographic lidar data is first downloaded from NOAA then loaded into ArcMap (version 10.4.1), gridded and contoured. This is done by the following steps:
    A) The LAS (x,y,z) data files were downloaded from NOAA in UTM, zone 19 (NAD83, NAVD88).
    B) The LAS files loaded into ArcMap: ArcToolbox >> Data Management >> LAS Dataset >> Create LAS Dataset.
    C) A DEM was created: ArcToolbox >> Conversion Tools >> To Raster >> LAS Dataset to Raster.
    D) The MTL was then contoured: ArcToolbox >> 3D Analyst Tools >> Raster Surface >> Contour.
    E) This contour was smoothed: ArcTools >> Cartography Tools >> Generalization >> Smooth Line, using PAEK smoothing at 100 m. The amount of smoothing was occasionally adjusted to improve the results.
    F) This line will be used as a baseline, so sections of the line in areas where we did not need to find a shoreline were removed (using the Arc editor). Where appropriate, disconnected sections of the line were joined with the Arc editor.
    G) The final lines were converted to points: ArcToolbox >> X Tools Pro >> Feature Conversions >> Convert Features to points and ArcToolbox >> Data Management Tools >> Features >> Add XY.
    F) The MTL contour was exported as a CSV file.
    This line is the baseline that will be used in the next step. Person who carried out this activity:
    Amy S. Farris
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    USA

    508-548-8700 x2344 (voice)
    508-457-2310 (FAX)
    afarris@usgs.gov
    Data sources used in this process:
    • 2013-2014 Lidar data
    Data sources produced in this process:
    • MTL contour for each analyzed area
    Date: 2017 (process 3 of 6)
    All the work in this process step is done separately on each marsh area. In this step the baseline from the previous step is loaded into Matlab (version 2017a) with the elevation data. The baseline is used to define transects and the elevation along each transect is found from the elevation data. The max slope along each transect is found and defined to be the marsh edge. This is done by the following steps:
    A) The same LAS files from the previous step were loaded into Matlab.
    B) A DEM was made from them (using the function griddata).
    C) The baseline made in the previous step was also loaded into Matlab.
    D) Transects are made: Equally spaced points (at 5m intervals) were found along this baseline. At each point a line perpendicular to the baseline was calculated (this is called a transect). The line extends out from both sides of the baseline. The length of each transect varied but was usually about 20-40m long.
    E) The elevation along each transect was extracted from the DEM (using the interp2 function).
    F) The marsh edge was defined to be the maximum slope along each transect between mean high water and (mean tide level - 0.5 m).
    Thus for each transect, we have an estimate of the shoreline position along that transect. Person who carried out this activity:
    Amy S. Farris
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    United States

    508-548-8700 x2344 (voice)
    508-457-2310 (FAX)
    afarris@usgs.gov
    Data sources used in this process:
    • MTL contour for each analyzed area
    • 2013-2014 Lidar data
    Data sources produced in this process:
    • raw marsh edge for each area analyzed
    Date: 2017 (process 4 of 6)
    All the work in this process step is done separately on each marsh area. In Matlab (version 2017a), the marsh edge found in the previous step was smoothed using a Gaussian weighted moving average with a 25 m window. Spurious points from the marsh line were removed using an interactive GUI in which the LAS data were plotted as dots color-coded by height with the marsh shoreline plotted on top. To aide decision making, the marsh edge was also displayed in Google Earth. It was helpful to look at images from different stages of the tidal cycle. Once this quality control check was done, the data were exported to a new shapefile (using the function shapewrite in the Mapping Toolbox, version 4.5.1). Person who carried out this activity:
    Amy S. Farris
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    United States

    508-548-8700 x2344 (voice)
    508-457-2310 (FAX)
    afarris@usgs.gov
    Data sources used in this process:
    • raw marsh edge edge for each area analyzed
    Data sources produced in this process:
    • preliminary marsh edge shapefiles for each area analyzed
    Date: 2018 (process 5 of 6)
    After the above steps were completed for each marsh area, the shapefiles for all regions were loaded into ArcMap (version 10.4.1) and plotted on NAIP imagery. Sections on sandy beaches were removed. There are many fringing marshes in the state. In these areas, both the mean high water (MHW) shoreline and the marsh edge were kept, because both have value. Since it is sometimes difficult in imagery to distinguish sand, mud and brown marsh grass, and since we did not want to delete valid marsh sections, when in doubt, we kept the marsh shoreline even if it might be on a small sandy area. A new attribute called “MarhType” was added. It was set to “platform” if the marsh looked like a platform marsh. It was set to “fringing” if the marsh looked like a fringing marsh. It was set to “unknown” if it was not clear if the area was really a marsh. Note that all choices were subjective and based only on visual interpretation of the imagery. All the individual shapefiles were joined into one shapefile for the whole state using Merge (ArcToolbox >> Data Management toolbox >> General >> Merge). The data were transformed from UTM zone 19 (NAD83) to geographic (WGS84) using ArcToolbox>>Data Management tools>>Projections and transformations>>Project. The software used the transromation WGS_1984_(ITRF00)_To_NAD_1983. Person who carried out this activity:
    Amy S. Farris
    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA
    United States

    508-457-8700 x2344 (voice)
    508-457-2310 (FAX)
    afarris@usgs.gov
    Data sources used in this process:
    • preliminary marsh edge shapefiles edge for each area analyzed
    • NAIP imagery
    Data sources produced in this process:
    • final marsh edge shapefile
    Date: 07-Aug-2020 (process 6 of 6)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  3. What similar or related data should the user be aware of?
    Smith, Theresa L., Himmelstoss, Emily A., and Thieler, E. Rober, 2013, Massachusetts Shoreline Change Project: A GIS Compilation of Vector Shorelines and Associated Shoreline Change Data for the 2013 Update: Open-File Report 2012-1183, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details: USGS Open File Report 2012-1183
    Thieler, E. Robert, O’Connell, James F., and Schupp, Courney A., 20010904, The Massachusetts Shoreline Change Project—1800s to 1994.

    Online Links:

    Weber, Kathryn M., List, Jeffery H., and Karen L. M. Morgan, 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:

    Other_Citation_Details: USGS Open File Report 2005-1027
    NOAA, Office of Coast Survey, Center for Operational Oceanographic Products and Services, and Survey, National Geodetic, 2013, VDatum.

    Online Links:

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

  1. How well have the observations been checked?
    Results were compared to drone imagery at a small test site in Eastham (Sherwood, 2016 - see Source Information). The marsh edge was usually within 2 m of a visible edge in the drone imagery. The drone imagery is accurate to approximately 3 m.
  2. How accurate are the geographic locations?
    This method identifies the maximum slope from a 2013-2014 lidar data set (USGS and others, 2015 – in the source contributions). The lidar data have a horizontal accuracy of 0.42 meters at 95 percent confidence level. This maximum slope is used as a proxy for the marsh edge. Visual comparisons of the smoothed edge to ortho-imagery (NAIP, nominal accuracy 5 m) are usually within 5 meters of a visually identifiable marsh edge.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    A shoreline was not found for every salt marsh in the state. Shorelines were calculated wherever shorelines were found for the previous Massachusetts Shoreline Change Project update (Smith and others, 2013). This data release includes additional data from Pleasant Bay on Cape Cod. In some areas the lidar data did not extend far enough off-shore to cover the entire fringing marsh and thus no marsh edge exists even though a fringing marsh is present. This was particularly true in south Wellfleet.
  5. How consistent are the relationships among the observations, including topology?
    This method uses elevation data to find the maximum slope. It will find a max slope on most types of morphology, not just marshes. The shoreline was plotted over imagery and solutions that were obviously not on a marsh were removed. If it was not clear whether or not the shoreline was on a marsh, the attribute “MarshType” was set to “unknown”.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Use_Constraints:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO
    United States

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? The zip file MA_marsh_edge.zip contains the marsh edge shapefile (MA_marsh_edge_2013_2014.shp and other shapefile component files), the browse graphic (browseGraphic.png), and the FGDC CSDGM metadata in XML format.
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials.
    Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  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: 07-Aug-2020
Metadata author:
Amy S. Farris
U.S. Geological Survey
384 Woods Hole Road
Woods Hole, MA
USA

508-548-8700 x2344 (voice)
508-547-2310 (FAX)
afarris@usgs.gov
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_F72R3QXR/MA_marsh_edge_2013_2014.faq.html>
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