Lifespan of marsh units in New York salt marshes (ver. 2.0, June 2026)

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Frequently anticipated questions:

What does this data set describe?

Title:
Lifespan of marsh units in New York salt marshes (ver. 2.0, June 2026)
Abstract:
*This dataset is revised due to a revision of the Eastern Long Island dataset. Please see the process steps below for full details.* Lifespan of salt marshes in New York are calculated using conceptual marsh units defined by Defne and Ganju (2018) and Welk and others (2019, 2020a, 2020b, 2020c). The lifespan calculation is based on estimated sediment supply and sea-level rise (SLR) predictions after Ganju and others (2020). Sea level predictions are local estimates which correspond to the 0.3, 0.5, and 1.0 meter increase in Global Mean Sea Level (GMSL) scenarios by 2100 from Sweet and others (2022). The U.S. Geological Survey has been expanding national assessment of coastal change hazards and forecast products to coastal wetlands with the intent of providing Federal, State, and local managers with tools to estimate the vulnerability and ecosystem service potential of these wetlands. For this purpose, the response and resilience of coastal wetlands to physical factors need to be assessed in terms of the ensuing change to their vulnerability and ecosystem services.
  1. How might this data set be cited?
    Defne, Zafer, Ganju, Neil K., and Ackerman, Kate V., 20240402, Lifespan of marsh units in New York salt marshes (ver. 2.0, June 2026): data release DOI:10.5066/P14MB99B, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Defne, Z., Ganju, N.K., and Ackerman, K.V., 2024, Lifespan of marsh units in New York salt marshes (ver 2.0, June 2026): U.S. Geological Survey data release, https://doi.org/10.5066/P14MB99B.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -74.2460
    East_Bounding_Coordinate: -71.8853
    North_Bounding_Coordinate: 41.6797
    South_Bounding_Coordinate: 40.5021
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/65b3ee2fd34e36a390458aa4/?name=mu_lifespan_NY.png&allowOpen=true (PNG)
    Graphic of shapefile showing lifespan estimates for New York salt marshes.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2024
    Currentness_Reference:
    publication date of original release
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: Vector Digital Data Set (Polygon)
  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):
      • G-polygon (9260)
    2. What coordinate system is used to represent geographic features?
      The map projection used is WGS 1984 Web Mercator Auxiliary Sphere (Esri Full Name: WGS_1984_Web_Mercator_Auxiliary_Sphere).
      Projection parameters:
      Standard_Parallel: 0.0
      Longitude_of_Central_Meridian: 0.0
      False_Easting: 0.0
      False_Northing: 0.0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.6096
      Ordinates (y-coordinates) are specified to the nearest 0.6096
      Planar coordinates are specified in meters
      The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
  7. How does the data set describe geographic features?
    mu_lifespan_NY.shp Attribute Table
    Attribute information associated with the lifespan estimates for the conceptual marsh units of New York salt marsh system. (Source: USGS)
    FID
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: Esri) Coordinates defining the features.
    FID_CMU
    Sequential unique whole number that represents the identification number for each conceptual marsh unit. Note that the FID_CMU values in this new dataset (version 2) do not correspond to the FID_CMU values in the original dataset (version 1) due to the incorporation of the updated Eastern Long Island dataset. (Source: USGS)
    Range of values
    Minimum:0
    Maximum:9259
    Units:none
    ATOT_M2
    Total surface area of a marsh unit in square meters. (Source: USGS)
    Range of values
    Minimum:1.31596
    Maximum:752436.67151
    Units:square meter
    AVEG_M2
    Surface area of vegetated part of a marsh unit in square meters. (Source: USGS)
    Range of values
    Minimum:0.0
    Maximum:721313.980396
    Units:square meter
    MU_ELEV
    Mean elevation of a marsh unit in meters referenced to NAVD88. (Source: USGS)
    ValueDefinition
    -9999No Data
    Range of values
    Minimum:-4.083
    Maximum:8.554
    Units:meter
    MU_ELEVMTL
    Mean elevation of a marsh unit in meters referenced to MTL. (Source: USGS)
    ValueDefinition
    -9999No Data
    Range of values
    Minimum:-4.003
    Maximum:8.554
    Units:meter
    VG_ELEV
    Mean elevation of the vegetated area in a marsh unit in meters referenced to NAVD88. Value is set to -9999 if there is no vegetated area in the marsh unit. (Source: USGS)
    ValueDefinition
    -9999No Data
    Range of values
    Minimum:-4.051
    Maximum:6.8245
    Units:meter
    VG_ELEVMTL
    Mean elevation of the vegetated area in a marsh unit in meters referenced to MTL. Value is set to -9999 if there is no vegetated area in the marsh unit. (Source: USGS)
    ValueDefinition
    -9999No Data
    Range of values
    Minimum:-3.971
    Maximum:6.931
    Units:meter
    UVVR
    Ratio of unvegetated surface area to vegetated surface area. Ordinarily, UVVR ranges from zero (completely vegetated) to infinity (completely unvegetated). However, it is assigned the value of -1 when completely unvegetated. (Source: USGS)
    Range of values
    Minimum:-1.0
    Maximum:6004.93552
    Units:none
    BGRND
    Lifespan for a marsh unit (in years) for nonclimatic background relative sea level rise. Negative lifespan (other than No Data) indicates the estimated lifespan is depleted and loss is imminent. (Source: USGS)
    ValueDefinition
    -9999No Data
    10000Value larger than or equal to 10000
    Range of values
    Minimum:-1336
    Maximum:10000
    Units:year
    GMSL03
    Lifespan for a marsh unit (in years) for global mean sea level rise of 0.3 meters by 2100. Negative lifespan (other than No Data) indicates the estimated lifespan is depleted and loss is imminent. (Source: USGS)
    ValueDefinition
    -9999No Data
    10000Value larger than or equal to 10000
    Range of values
    Minimum:-690
    Maximum:10000
    Units:year
    GMSL05
    Lifespan for a marsh unit (in years) for global mean sea level rise of 0.5 meters by 2100. Negative lifespan (other than No Data) indicates the estimated lifespan is depleted and loss is imminent. (Source: USGS)
    ValueDefinition
    -9999No Data
    10000Value larger than or equal to 10000
    Range of values
    Minimum:-407
    Maximum:10000
    Units:year
    GMSL10
    Lifespan for a marsh unit (in years) for global mean sea level rise of 1.0 meters by 2100. Negative lifespan (other than No Data) indicates the estimated lifespan is depleted and loss is imminent. (Source: USGS)
    ValueDefinition
    -9999No Data
    10000Value larger than or equal to 10000
    Range of values
    Minimum:-279
    Maximum:10000
    Units:year
    FLG
    Marsh unit flag indicating anomalous marsh units based on absence of vegetation, elevation, surface area and tidal range extrapolation. FLG values indicate: (-1) no vegetated area in the marsh unit; (-10) marsh unit elevation higher than the 99.8 percentile; (-100) marsh unit elevation less than the 0.2 percentile; (-200) greater than 25 percent of the marsh unit elevation is hydro-flattened; (-1000) marsh unit surface area less than 900 m^2; (-10000) mean tidal range of marsh unit is extrapolated; and (0) no flag. Combination of negative values indicates a combination of flags. For example, -1001 indicates no vegetated area and area less than 900 m^2. (Source: USGS)
    Range of values
    Minimum:-11201
    Maximum:0
    Units:None
    Reg_FIDCMU
    This field contains the region and FID_CMU of the source datasets. The regions are: (1) Hudson Valley and New York City (2) North shore Long Island (3) Eastern Long Island (4) Fire Island National Seashore and central Great South Bay (5) Jamaica Bay to western Great South Bay. (Source: USGS) The concatenation of the region and FID_CMU of the source dataset
    Entity_and_Attribute_Overview:
    In this dataset, lifespan estimates for each conceptual salt marsh unit in the New York salt marsh system has been calculated based on the 1-meter resolution raster source dataset. Decimal values in the attribute table are a result of double precision calculations while significant digits are considered in defining the attribute measurement resolutions. Therefore, the smallest unit increment for area values and elevation is assumed to be 1 meter and 0.01, respectively.
    Entity_and_Attribute_Detail_Citation: USGS

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Zafer Defne
    • Neil K. Ganju
    • Kate V. Ackerman
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Zafer Defne
    Oceanographer
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2254 (voice)
    508-457-2310 (FAX)

Why was the data set created?

The purpose of this shapefile is to present lifespan estimates for each salt marsh unit in New York as defined by the USGS (Defne and Ganju, 2018; Welk and others, 2019, 2020a, 2020b, 2020c).

How was the data set created?

  1. From what previous works were the data drawn?
    mu_elev_FIIS (source 1 of 6)
    Defne, Zafer, and Ganju, Neil K., 2018, Elevation of marsh units in Fire Island National Seashore and Central Great South Bay salt marsh complex, New York: data release DOI:10.5066/P91K4FZP, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Used the marsh unit elevation (MU_ELEV) and vegetated fraction elevation (VG_ELEV) as inputs. Projection was WGS 1984 Web Mercator Auxiliary Sphere. Data was downloaded 09/16/2019.
    mu_UVVR_FIIS (source 2 of 6)
    Defne, Zafer, and Ganju, Neil K., 2018, Unvegetated to vegetated marsh ratio in Fire Island National Seashore and Central Great South Bay salt marsh complex, New York: data release DOI:10.5066/P9RHUSWY, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    Used the unvegetated to vegetated ratio (UVVR) as input. Projection was WGS 1984 Web Mercator Auxiliary Sphere. Data was downloaded 09/16/2019.
    mu_elev_JB; mu_UVVR_JB (source 3 of 6)
    Welk, Robert J., Defne, Zafer, and Ganju, Neil K., 2019, Coastal wetlands from Jamaica Bay to western Great South Bay, New York: data release DOI:10.5066/P9GAGLXB, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    From the elevation dataset, we used the marsh unit elevation (MU_ELEV) and vegetated fraction elevation (VG_ELEV) as inputs. From the unvegetated to vegetated ratio (UVVR) dataset, we used the UVVR as input. Projection was WGS 1984 Web Mercator Auxiliary Sphere. Data was downloaded 06/03/2020.
    mu_elev_NSLI; mu_UVVR_NSLI (source 4 of 6)
    Welk, Robert J., Defne, Zafer, and Ganju, Neil K., 2020, Coastal wetlands of north shore Long Island, New York: data release DOI:10.5066/P9UNOMM8, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    From the elevation dataset, we used the marsh unit elevation (MU_ELEV) and vegetated fraction elevation (VG_ELEV) as inputs. From the unvegetated to vegetated ratio (UVVR) dataset, we used the UVVR as input. Projection was WGS 1984 Web Mercator Auxiliary Sphere. Data was downloaded 06/03/2020.
    mu_elev_HvNYC; mu_UVVR_HvNYC (source 5 of 6)
    Welk, Robert J., Defne, Zafer, and Ganju, Neil K., 2020, Coastal wetlands of Hudson Valley and New York City, New York: data release DOI:10.5066/P9XV0JMJ, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    From the elevation dataset, we used the marsh unit elevation (MU_ELEV) and vegetated fraction elevation (VG_ELEV) as inputs. From the unvegetated to vegetated ratio (UVVR) dataset, we used the UVVR as input. Projection was WGS 1984 Web Mercator Auxiliary Sphere. Data was downloaded 02/11/2021.
    mu_elev_ELI; mu_UVVR_ELI (source 6 of 6)
    Welk, Robert J., Ackerman, Kate V., Defne, Zafer, and Ganju, Neil K., 2020, Coastal wetlands of eastern Long Island, New York (ver. 3.0, May 2026): data release DOI:10.5066/P91H426U, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: online
    Source_Contribution:
    From the elevation dataset, we used the marsh unit elevation (MU_ELEV) and vegetated fraction elevation (VG_ELEV) as inputs. From the unvegetated to vegetated ratio (UVVR) dataset, we used the UVVR as input. Projection was WGS 1984 Web Mercator Auxiliary Sphere. Data was downloaded 05/25/2026.
  2. How were the data generated, processed, and modified?
    Date: 2024 (process 1 of 6)
    Process step 1. This process step was performed by Kate Ackerman, using ArcGIS Pro (ver.2.8.8). For simple operations the name of the geoprocessing tool used is given in capital letters; for complex operations, the name of the geoprocessing tool used is given in capital letters and any critical parameters used are given in parentheses, separated by a semicolon, immediately after the tool name. The input and output file names are provided in [square brackets] when necessary. Units for length and area calculations are meters (m) and square meters (m2) unless otherwise stated.
    Merge input datasets.
    a) Download elevation (mu_elev_HvNYC.shp, mu_elev_NSLI.shp, mu_elev_ELI.shp, mu_elev_FIIS.shp, mu_elev_JB.shp) and unvegetated to vegetated marsh ratio (UVVR) (mu_UVVR_HvNYC.shp, mu_UVVR_NSLI.shp, mu_UVVR_ELI.shp, mu_UVVR_FIIS.shp, mu_UVVR_JB.shp) layers from the publications that cover the salt marshes of New York. For each dataset (elevation and UVVR), add a new field (Reg_FIDCMU) to include the concatenation of the region and FID_CMU of the source datasets. The region values are: (1) Hudson Valley and New York City (2) North Shore Long Island (3) Eastern Long Island (4) Fire Island National Seashore and central Great South Bay (5) Jamaica Bay to western Great South Bay.
    b) MERGE the elevation datasets to create one dataset for New York. MERGE the UVVR datasets to create one dataset for New York.
    c) JOIN (Join field= Reg_FIDCMU) the New York elevation and UVVR datasets to create one shapefile with both datasets in it.
    d) Convert the coordinate system from Web Mercator to the North American Datum of 1983 (NAD 1983) geographic coordinate system and add the coordinates for polygon centroids (X_POINT, Y_POINT) in decimal degrees to the data table using CALCULATE_GEOMETRY_ATTRIBUTES tool.
    e) Export following variables to a comma separated values file [NY_mu.csv]: X_POINT, Y_POINT, FID_CMU, UVVR, ATOT_M2, AVEG_M2, mu_ELEV, vg_ELEV, FLG. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Kate Ackerman
    Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2331 (voice)
    508-457-2310 (FAX)
    Data sources used in this process:
    • mu_elev_HvNYC
    • mu_elev_NSLI
    • mu_elev_ELI
    • mu_elev_FIIS
    • mu_elev_JB
    • mu_UVVR_HvNYC
    • mu_UVVR_NSLI
    • mu_UVVR_ELI
    • mu_UVVR_FIIS
    • mu_UVVR_JB
    Data sources produced in this process:
    • NY_mu.csv
    Date: 2024 (process 2 of 6)
    Process step 2. This processing steps was performed by Zafer Defne using VDatum online (VDatum ver.4.6.1) and Matlab (ver.2021b).
    Convert datums and calculate lifespan.
    a) Convert marsh unit elevations from the North American Vertical Datum of 1988 (NAVD88) to Mean Tide Level (MTL) referenced elevations.
    Input the ASCII file of latitude and longitude coordinates and elevation from NY dataset (NY_mu.csv) to VDatum software, and transform vertical datum from the NAVD88 to MTL. Do this for the marsh unit elevation (MU_ELEV) and elevation of the vegetated part of the marsh unit (VG_ELEV) to calculate MU_ELEV_MTL and VG_ELEV_MTL, respectively. Use value from the nearest Vdatum point for any point where VDatum has no data.
    b) Calculate sediment budget from UVVR based on Ganju and others (2020) with SB=-0.416*log(UVVR)-1.0749, where SB is sediment budget in kilograms per square meter per year, and log() indicates natural logarithm function.
    c) Calculate total sediment flux under background relative SLR (BGRND) with SF=SB*ATOT_M2, where SF is sediment flux in kilograms per year and ATOT_M2 is total surface area of marsh unit in square meters.
    d) Calculate total sediment flux under global mean sea level (GMSL) scenarios (for example, GMSL03 scenario means GMSL rise of 0.3 meters). SLR reduces vegetated marsh area, therefore, causes reduction in sediment flux. The sediment flux under SLR is calculated with SF_SLR=(SB-SLR_RATE*RHO_F)*ATOT_M2, where SF_SLR is sediment flux under SLR, RHO_F is dry bulk density of future deposited sediment. RHO_F was assigned 159 kilograms per cubic meters from Morris and others (2016). SLR_RATE is the SLR rate, calculated as SLR_RATE=(RSL2100+RSL_OFFSET)/100-RSL_VLM, where RSL2100 is the relative sea level by 2100 under a global mean sea level rise scenario, RSL_OFFSET is the offset to initiate the projection at year 2000, and RSL_VLM is the relative sea level contribution from vertical land motion.
    For sea level rise projections, Sweet and others (2022) SLR data within the region were used. A total of 29 points including 14 stations and 15 grid points were within the bounding box with lower left corner of (39.9333N, -75.1417W) and upper right corner of (42.3539N, -71.0000W).
    Interpolate the SLR_RATE from 29 points over a regular grid using GRIDDATA function with natural neighbor interpolation (grid size by 41 longitudinal by 24 latitudinal points). Assign to each marsh unit the interpolated SLR_RATE value from the nearest grid point. Do this for the three scenarios considered: GMSL rise of 0.3 meters, 0.5 meters and 1.0 meters by year 2100 and calculate sediment flux for each of them.
    e) Total sediment mass in the vegetated plain above MTL is calculated with TS=vg_ELEV_MTL*AVEG_M2*RHO_E, where TS is total sediment mass, AVEG_M2 is the surface area of the vegetated part of the marsh unit and RHO_E is the dry bulk density of existing marsh substrate sediment. RHO_E was assigned 373 kilograms per cubic meters from Morris and others (2016).
    f) Calculate lifespan (in years) for the background relative SLR with the equation BGRND= -TS/SF. Calculate lifespan (in years) for global mean sea level rise by 0.3 meters, 0.5 meters and 1.0 meters by year 2100 scenarios with the equation GMSL= -TS/SF_SLR for each scenario (GMSL03, GMSL05, GMSL10, respectively).
    g) Output Matlab data as a comma separated text file [NY_lifespan.csv]. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Zafer Defne
    Oceanographer
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2254 (voice)
    508-457-2310 (FAX)
    Data sources used in this process:
    • NY_mu.csv
    Data sources produced in this process:
    • NY_lifespan.csv
    Date: 2024 (process 3 of 6)
    Process step 3. This processing step was performed by Zafer Defne using ArcGIS Pro (ver. 3.0.3).
    Finalize the feature dataset and change projection.
    a) JOIN lifespan calculation results file with the marsh unit features using ADD_JOIN and join field as FID_CMU.
    b) For marshes that are more stable, lifespan calculation sometimes results in large numbers that are far beyond the lifespan horizon of interest. Also, positive sediment budget implies unlimited lifespan. For these units, set the maximum lifespan value to 10,000 years.
    c) Set lifespan values to -9999 for units with no vegetated area or with missing elevation values (FLG values that contain any of -1 or -200 values in them) so that they can be labeled as not available or excluded while plotting the data.
    d) Set legend label for lifespan values less than 0 as imminent.
    e) Rearrange field names and change the projection for better performance of web services with online base maps. PROJECT(Input coordinate system= NAD 1983 Geographic coordinate system; Output coordinate system=WGS 1984 Web Mercator Auxiliary Sphere; Geographic transformation= WGS 1984 (ITRF00) to NAD 1983) the feature dataset to obtain the lifespan values [mu_lifespan_NY.shp]. Data sources used in this process:
    • NY_lifespan.csv
    Data sources produced in this process:
    • mu_lifespan_NY.shp
    Date: 29-May-2026 (process 4 of 6)
    This and the following three process steps describe the updates made for version 2 of this dataset. This and the following process steps were completed by Kate Ackerman.
    The New York lifespan dataset required revision because one of its inputs- the Eastern Long Island study area- was updated (Welk, R.J., Ackerman, K.V., Defne, Z., and Ganju, N.K., 2020, Coastal wetlands of eastern Long Island, New York (ver. 3.0, May 2026): U.S. Geological Survey data release, https://doi.org/10.5066/P91H426U.).
    The Eastern Long Island dataset was updated to version 3 in May 2026 to subdivide the marsh plains into smaller "marsh units," a step that had not been completed in the original dataset.
    Using the revised Eastern Long Island dataset (version 3), new lifespan values were calculated for the newly defined marsh units in the Eastern Long Island study area. These updated lifespan values were then incorporated into the New York lifespan dataset.
    Updates were performed in ArcGIS Pro 3.4.3. The above process steps (steps 1-3) were followed using the new Eastern Long Island marsh unit data as the input to calculate lifespan values for Eastern Long Island:
    Process step 1(c-e) was followed using the updated Eastern Long Island marsh unit UVVR and elevation datasets.
    Process Step 2 was followed using the new Eastern Long Island merged dataset to convert datums and calculate lifespan. For step 2(d), Python was used instead of Matlab. The bounding box information is: A total of 15 points including 6 stations and 9 grid points were within the bounding box with lower left corner of (40.0000N, -73.1817W) and upper right corner of (42.0000N, -71.0000W). Interpolate the SLR_RATE from 15 points over a regular grid using SciPy Griddata function with linear interpolation (grid size by 22 longitudinal by 20 latitudinal points).
    Process Step 3 was followed using the new Eastern Long Island marsh unit dataset.
    Date: 29-May-2026 (process 5 of 6)
    To update the NY lifespan dataset, the original Eastern Long Island lifespan data was first removed from the NY lifespan shapefile. The new Eastern Long Island lifespan values were then added to the shapefile.
    As part of this update, all original FID_CMU values were deleted from the New York lifespan dataset. New FID_CMU values were calculated to be equal to the FID value. Because of these changes, the FID_CMU values in version 2 do not correspond to those in version 1.
    Date: 29-May-2026 (process 6 of 6)
    Removed the web services distribution formats. ScienceBase will be changing platforms and those services will no longer be available.
  3. What similar or related data should the user be aware of?
    Ganju, N.K., Defne, Z., and Fagherazzi, S., 2020, Are elevation and open-water conversion of salt marshes connected?: Geophysical Research Letters v. 47, issue 3.

    Online Links:

    Morris, J.T., Barber, D.C., Callaway, J.C., Chambers, R., Hagen, S.C., Hopkinson, C.S., Johnson, B.J., Megonigal, P., Neubauer, S.C., Troxler, T., and Wigand, C., 2016, Contributions of organic and inorganic matter to sediment volume and accretion in tidal wetlands at steady state: Earth’s Future v. 4, issue 4.

    Online Links:

    Sweet, W.V., Hamlington, B.D., Kopp, R.E., Weaver, C.P., Barnard, P.L., Bekaert, D., Brooks, W., Craghan, M., Dusek, G., Frederikse, T., Garner, G., Genz, A.S., Krasting, J.P., Larour, E., Marcy, D., Marra, J.J., Obeysekera, J., Osler, M., Pendleton, M., Roman, D., Schmied, L., Veatch, W., White, K.D., and Zuzak, C., 2022, Global and Regional Sea Level Rise Scenarios for the United States: Updated Mean Projections and Extreme Water Level Probabilities Along U.S. Coastlines: NOAA, Silver Spring, MD.

    Online Links:

    Defne, Zafer, and Ganju, Neil K., 2018, Conceptual marsh units for Fire Island National Seashore and central Great South Bay salt marsh complex, New York: data release DOI:10.5066/P95U2MQ7, U.S. Geological Survey, Reston, VA.

    Online Links:

    Welk, Robert J., Defne, Zafer, and Ganju, Neil K., 2019, Coastal wetlands from Jamaica Bay to western Great South Bay, New York: data release DOI:10.5066/P9GAGLXB, U.S. Geological Survey, Reston, VA.

    Online Links:

    Welk, Robert J., Defne, Zafer, and Ganju, Neil K., 2020, Coastal wetlands of north shore Long Island, New York: data release DOI:10.5066/P9UNOMM8, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    This is referred to as "Welk and others (2020a)" throughout this metadata.
    Welk, Robert J., Defne, Zafer, and Ganju, Neil K., 2020, Coastal wetlands of Hudson Valley and New York City, New York: data release DOI:10.5066/P9XV0JMJ, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    This is referred to as "Welk and others (2020b)" throughout this metadata.
    Welk, Robert J., Ackerman, Kate V., Defne, Zafer, and Ganju, Neil K., 2020, Coastal wetlands of eastern Long Island, New York (ver. 3.0, May 2026): data release DOI:10.5066/P91H426U, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    This is referred to as "Welk and others (2020c)" throughout this metadata.

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

  1. How well have the observations been checked?
    Marsh units, and water and land boundaries inherit their accuracy from accuracy of the source data, New York marsh units. The vertical accuracy of the marsh unit elevation is inherited from the 1-meter resolution U.S. Geological Survey Coastal National Elevation Database (USGS CoNED) data. The uncertainty in the lifespan estimates is large because of the nature of the empirical equations used and the uncertainty in the source data. For example, a 20% variation in each of the unvegetated to vegetated marsh ratio (UVVR), elevation, bulk density and sea-level rise variables, when all in favor of reducing lifespan, may result in a combined reduction of 50% in lifespan estimate.
  2. How accurate are the geographic locations?
    Horizontal accuracy is inherited from the source dataset that delineates the marsh units, and can be considered to be +/-6 meters.
  3. How accurate are the heights or depths?
    Because the elevation values are averaged over delineated polygons, vertical accuracy of marsh unit elevation depends on both the horizontal accuracy of NWI dataset and the vertical accuracy of source elevation data. CoNED vertical elevation accuracy was 0.2 meters. No additional accuracy assessment of the vertical accuracy has been conducted.
  4. Where are the gaps in the data? What is missing?
    The results are specific to the marsh polygons definition within the boundaries of the New York salt marsh system. A detailed on-the-ground analysis of a single site may result in a different interpretation of the wetland and marsh unit boundaries.
  5. How consistent are the relationships among the observations, including topology?
    Negative lifespan indicates the estimated lifespan is depleted and loss is imminent. Some flagged units (see description for the FLG variable) are assigned a lifespan estimate of -9999.

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. The lifespan estimate for each marsh unit is defined for scientific research purposes and should not be used as a sole source of reference for any regulations and policy making.
  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

    1-888-275-8747 (voice)
  2. What's the catalog number I need to order this data set? The dataset contains polygon marsh unit lifespan data (mu_lifespan_NY.shp and other shapefile components), browse graphic, and the FGDC CSDGM metadata in .xml format.
  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. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 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. Not for navigational use.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 22-Jun-2026
Metadata author:
U.S. Geological Survey
Attn: Zafer Defne
Oceanographer
384 Woods Hole Road
Woods Hole, MA

508-548-8700 x2254 (voice)
508-457-2310 (FAX)
Contact_Instructions:
The metadata contact email address is a generic address in the event the person is no longer with USGS.
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P14MB99B/mu_lifespan_NY.faq.html>
Generated by mp version 2.9.51 on Mon Jun 22 14:43:10 2026