Alexander C. Seymour Kara S. Doran 20260310 1.0 vector digital data Alexander C. Seymour Kara S. Doran 20260310 U.S. Geological Survey data release doi:10.5066/P9WYA19U St. Petersburg, FL U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center https://doi.org/10.5066/P9WYA19U The U.S. Geological Survey (USGS) supports multiple efforts to understand and predict storm impacts to our nation’s coastlines. The geospatial dataset (vector feature class) and comma-delimited American Standard Code for Information Interchange (ASCII) table describes the changes in the elevation and cross-shore position of the modern foredune crest from September 1997 to October 2018 across the North Carolina ocean-fronted coastline, as well as infrastructure distance, beach width, and total water level (TWL) elevation information. Results are provided as points at an alongshore resolution of 500 meters (m) and describe the dune crest elevation (classified as ‘low’, ‘moderate’, or ‘high’), the dune crest elevation trend (classified as ‘eroding’, ‘no net change’, or ‘accreting’), and the dune crest migration trend (classified as ‘landward’, ‘no net change’, or ‘seaward’). The cross-shore distance between the dune crest and line of first infrastructure at the end of the study period, average beach width, and 98% quantile total water level elevation for the study period are also provided. Individual dune condition code positions (points) represent the center of an alongshore “bin” and describe coastal trends within 250 m alongshore on either side of the point. An ArcGIS Pro Map Package file is also included, which displays dune condition code and time series features with specific symbology and graphing schema that aid the user in interpreting and visualizing some of the most important attributes in the data. The methods used to generate this data followed the process outlined in “Decadal-scale characteristics of natural and anthropogenic dune morphology along North Carolina barrier islands (SE Atlantic coast)” by Seymour and others (2026). To provide information on the changes in the elevation and position of coastal dunes over the last two decades, along with beach width, total water level, and first infrastructure line distance data along the North Carolina coast. 19970915 20181002 ground condition Complete None planned -78.541634 -75.460637 36.546124 33.844975 USGS Metadata Identifier USGS:ff278ec5-35ce-415b-b0ae-652d7f91c337 ISO 19115 Topic Category geoscientificInformation oceans environment structure USGS Thesaurus hazards marine geology ocean sciences coastal processes erosion floods geospatial datasets time series datasets None U.S. Geological Survey USGS St. Petersburg Coastal and Marine Science Center SPCMSC Coastal and Marine Hazards and Resources Program CMHRP Geographic Names Information System (GNIS) North Carolina Atlantic Ocean None Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey requests to be acknowledged as originators of the data in future products or derivative research. U.S. Geological Survey Kara S. Doran mailing and physical

600 4th Street South

Saint Petersburg FL 33701 United States 727-502-8117 727-502-8001 kdoran@usgs.gov Windows 10 Enterprise 21H2 (Build 19044.1826); Esri ArcGIS Pro 2.7.1 Alexander C. Seymour Daniel J. Ciarletta Kara S. Doran Kai Parker Margaret L. Palmsten 20260305 Journal of Coastal Research Unknown https://doi.org/10.2112/JCOASTRES-D-25-00053.1 Uncertainty estimates were produced for all results. This dataset is considered complete for the information presented, as described in the abstract section. Users are advised to read the rest of the metadata record carefully for additional details. Uncertainties for rates of dune crest cross-shore migration are described by 95% confidence intervals. Uncertainties for time series beach slope and beach width are described by 95% confidence intervals. Confidence intervals are standard diagnostic metrics produced by generalized linear regressions. For more information on how these regressions were calculated, see Seymour and others (2024). Horizontal positions were projected to the World Geodetic System of 1984 (WGS 84) Universal Transverse Mercator Zone 18 North (UTM 18N) coordinate system. Uncertainties for final modeled dune elevations, as well as final modeled Q98 TWL (98% quantile total water level) elevations, are described by 95% prediction intervals for positions that are statistically increasing or decreasing, and by 95% confidence intervals for positions that are no net elevation change. Uncertainties for rates of dune crest elevation change are described by 95% confidence intervals. Uncertainties for mean time series dune crest elevation and Q98 TWL elevation are described by 95% confidence intervals. Confidence and prediction intervals are standard diagnostic metrics produced by generalized linear regressions. For more information on how these regressions were calculated, see Seymour and others (2024). Vertical positions were referenced to the North American Vertical Datum of 1988 (NAVD88). Methods for deriving spatial and time series data and attributes in this data release can be found in Seymour and others (2026). For final predicted dune crest elevations, if the dune crest was classified as increasing or decreasing in elevation across the time series, this value is the final dune crest elevation predicted by the regression at the end of the time series and the uncertainty is represented by the 95% prediction interval. If the dune crest was classified as no net change in elevation across the time series, this value is the mean dune crest elevation across the time series, and the uncertainty is represented by the 95% confidence interval for the time series mean. Final predicted dune crest cross-shore positions are not an independent attribute but were used during the calculation of the dune crest to infrastructure distance. For final predicted dune crest cross-shore positions, if the dune crest was classified as migrating seaward or landward across the time series, this value is the final dune crest position predicted by the regression at the end of the time series. If the dune crest was classified as no net change in position across the time series, this value is the mean dune crest position across the time series. For the final predicted 98% quantile total water level elevation, if 98% quantile total water level elevation was classified as increasing or decreasing across the time series, this value is the final elevation predicted by the time series regression, and the uncertainty is represented by the 95% prediction interval. If the 98% quantile total water level elevation was classified as no net change across the time series, this value is the mean 98% quantile total water level elevation across the time series, and the uncertainty is represented by the 95% confidence interval for the time series mean. In the above attributes, final predicted values and time series means were used because they correct for interannual dune elevation, position, and Q98 TWL variance better than the observed dune elevations from the latest survey year. See Seymour and others (2026) for more information. Additionally, after the dune condition code features were generated, an analyst manually removed select positions that occurred in inlets where the elevation of shoals was contributing datapoints to the time series. This sometimes occurs after the erosive loss of the subaerial beach and results in inaccurate dune elevation and migration change trends. Additional points were removed that were calculated from transects that diverged from shore-normal orientations. Specifically, this could occur most often directly on cape headlands, or on spits adjoined to cape headlands. 20221013 NC_Dune_Condition_Codes_GDB Alexander C. Seymour U.S. Geological Survey Physical Scientist mailing and physical

600 4th Street South

Saint Petersburg FL 33701 United States 727-502-8122 727-502-8001 aseymour@usgs.gov The data included in this release is a point feature class of the dune condition codes stored in a file geodatabase (.gdb), along with a comma-delimited ASCII table (.csv) for users that do not have the ability to open and view Geographic Information Systems (GIS) file formats. The dune condition code ASCII table was generated by inputting the geodatabase feature class into the ‘Feature Class to ASCII’ ArcGIS Pro geoprocessing tool. NC_Dune_Condition_Codes_GDB 20221013 NC_Dune_Condition_Codes_ASCII Alexander C. Seymour U.S. Geological Survey Physical Scientist mailing and physical

600 4th Street South

Saint Petersburg FL 33701 United States 727-502-8122 727-502-8001 aseymour@usgs.gov To include additional visualizations of the feature class data, an ArcGIS Pro Map Package (.mpkx) was generated, which contains specific symbolization of the feature classes and charts that aid the user in interpreting and visualizing some of the most important attributes in the data. The geodatabase feature classes, both the dune condition code described in this metadata record (NC_Dune_Condition_Codes_GDB), and time series features (NC_Time_Series_Features_GDB, described in NC_Time_Series_Features_Metadata) were added to a new ArcGIS Pro map. Map symbology was established by setting the symbology type to Unique Values and selecting the ‘Elevation Condition’, ‘Elevation Trend’, and ‘Migration Trend’ fields, and classifying/coloring those symbol classes. The rational for the symbol types and colors are described in Seymour and Others (2024). Scatterplots displaying interannual dune elevation and cross shore position change were created by selecting the time series features and clicking on the scatter plot option under the Create Charts button within the Data toolbar tab. The ‘Survey Year’ field was chosen as the x-axis and the ‘Mean Dune Elevation’ or ‘Mean Dune Position’ was chosen as the y-axis. Bar charts displaying the frequency of dune condition codes were created by selecting the dune condition code features and clicking on the Bar Chart option under the Create Charts button within the Data toolbar tab. The ‘Condition Code’ field was chosen as the category variable and the Count option was chosen for aggregation. The Hybrid Reference Layer and World Imagery basemaps were also added to the map layout. For more information about these basemaps, refer to: Hybrid Reference Layer (https://www.arcgis.com/home/item.html?id=30d6b8271e1849cd9c3042060001f425) and World Imagery (https://services.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer). The map and its associated schema were then exported to a Map Package by clicking the ‘New Map Package’ command in the ‘Share’ tab in ArcGIS Pro. NC_Dune_Condition_Codes_Time_Series.gdb NC_Dune_Condition_Codes_GDB NC_Time_Series_Features_GDB 20221013 NC_Dune_Condition_Codes_Time_Series_Map_Pack.mpkx NC_Dune_Condition_Codes_Time_Series.zip Alexander C. Seymour U.S. Geological Survey Physical Scientist mailing and physical

600 4th Street South

Saint Petersburg FL 33701 United States 727-502-8122 727-502-8001 aseymour@usgs.gov Point Point 987 Universal Transverse Mercator 18N 0.9996 -75.0 0.0 500000.0 0.0 coordinate pair 0.001 0.001 meters WGS 1984 WGS 1984 6378137.0 298.257223563 North American Vertical Datum 1988 0.01 meters Attribute values NC_Dune_Condition_Codes_GDB.gdb, NC_Dune_Condition_Codes_ASCII.csv File geodatabase feature class (.gdb) and comma-separated values file (.csv) of the dune condition codes for North Carolina. USGS OBJECTID Internal feature number. Esri Sequential unique whole numbers that are automatically generated. Shape Feature geometry. This attribute is only present in the feature class dataset. Esri Vector type (Point M). AlongshoreID Unique ID for the alongshore bin. USGS 1 1033 ConditionCode A three-digit code describing the dune height class, dune elevation trend, and dune position trend. USGS The first digit describes the dune crest height class (1 = low, 2 = moderate, 3 = high), the second digit describes the dune crest elevation trend (1 = eroding, 2 = no net change, 3 = accreting), and the third digit describes the dune crest position trend (1 = transgressing, 2 = no net change, 3 = prograding). ElevationCondition A string describing the dune crest elevation condition class. USGS Low Dune crests that have a low time series mean elevation (less than 3.82 m). USGS Moderate Dune crests that have a moderate time series mean elevation (3.82 – 5.65 m). USGS High Dunes crests that have a high time series mean elevation (greater than 5.65 m). USGS MeanDuneElevation Spatiotemporal average dune crest elevation within each alongshore bin and across the entire time series, in meters NAVD88. USGS 1.380703 9.745357 MeanDuneElevationUncertainty 95% confidence interval describing the time series mean dune crest elevation uncertainty, in meters. USGS 0.055937 2.070284 DuneElevationSTD Standard deviation of the bin-averaged dune crest elevation across the entire time series, in meters. USGS 0.076808 1.972759 DuneElevationTrend A string describing the dune crest elevation trend. USGS Eroding Dune crests that are decreasing in elevation across the time series. USGS No net change Dune crests that are no net change in elevation across the time series. USGS Accreting Dune crests that are increasing in elevation across the time series. USGS DuneElevationChangeRate Estimated bin-averaged dune crest elevation change rate across the time series, in meters/year. If the rate was not statistically significant, the rate was recorded as zero. USGS -0.184645 0.163274 DuneElevationChangeRateUnfilt Estimated bin-averaged dune crest elevation change rate across the time series, in meters/year. Rates were unfiltered and not set to zero when not statistically significant. This attribute was included specifically to compare with the dune elevation change rate uncertainty, because rate uncertainties cannot be accurately applied to rates set to zero. USGS -0.184645 0.163274 DuneElevationChangeRateUncert One-tailed 95% confidence interval describing the dune crest elevation change rate uncertainty, in meters/year. USGS 0.003921 0.314643 MigrationTrend A string describing the dune crest migration trend. USGS Landward Dune crests that are migrating landward across the time series (transgressing). USGS No net change Dune crests that are no net change in position across the time series. USGS Seaward Dune crests that are migrating seaward across the time series (prograding). USGS DuneMigrationRate Cross-shore migration rate of bin-averaged dune crest positions across the time series, in meters/year. Negative rates indicate landward migration, and positive rates indicate seaward migration. If the rate was not statistically significant, the rate was recorded as zero. USGS -30.384809 19.207479 DuneMigrationRateUnfiltered Cross-shore migration rate of bin-averaged dune crest positions across the time series, in meters/year. Rates were unfiltered and not set to zero when not statistically significant. This attribute was included specifically to compare with the dune migration rate uncertainty, because rate uncertainties cannot be accurately applied to rates set to zero. Negative rates indicate landward migration, and positive rates indicate seaward migration. USGS -30.384809 19.207479 DuneMigrationRateUncertainty 95% percent confidence interval for the dune crest migration change rate, in meters/year. USGS 0.035645 24.040369 DunePositionSTD Standard deviation of the bin-averaged dune crest cross-shore position across the time series, in meters. USGS 0.349312 262.262146 MeanBeachWidth Mean bin-averaged beach width across the time series, in meters. Beach width was defined as the cross-shore planar distance between the mean high water shoreline and the dune toe. USGS 20.517197 259.278687 MeanBeachWidthUncertainty 95% confidence interval describing the time series mean beach width uncertainty, in meters. USGS 1.837929 221.239273 MeanBeachSlope Mean bin-averaged beach slope across the time series, in angular degrees. Beach slope was measured using the mean high water and dune toe position. USGS 0.770043 7.148379 MeanBeachSlopeUncertainty 95% confidence interval describing the time series mean beach slope uncertainty, in angular degrees. USGS 0.112394 5.998414 MeanDistDuneToInfrastructure The mean cross-shore distance between the final predicted dune crest position at the end of the time series and the bin-averaged position of the line of first infrastructure, in meters. Negative values indicate that the line of first infrastructure is seaward of the dune crest. Null values indicate that there was no infrastructure within 500 m of the shoreline. USGS -55.180721 435.653908 MedianDistDuneToInfrastructur The median cross-shore distance between the final predicted dune crest position and the bin-averaged position of the line of first infrastructure, in meters. Negative values indicate that the line of first infrastructure is seaward of the dune crest. Null values indicate that there was no infrastructure within 500 m of the shoreline. USGS -57.157335 471.220059 STDDuneToInfrastructure The standard deviation of the cross-shore distance between the final predicted dune crest position and the bin-averaged line of first infrastructure position, in meters. Null values indicate that there was no infrastructure within 500 m of the shoreline. USGS 0.683446 205.610771 FinalPredictedDuneElevation Predicted dune crest elevation at the end of the time series, in meters NAVD88. This is represented by either a regression prediction or a time series mean. Final predicted values and time series means were used because they correct for interannual dune elevation variance better than the observed dune elevations from the latest survey year. See Seymour and others (2024) for more information. USGS 1.076 10.222 FinalPredictedDuneElevUncerta Uncertainty for the final predicted dune elevation. This is represented by either a prediction interval or a confidence interval. See the Vertical_Positional_Accuracy_Report section of this metadata for more information. USGS 0.051 3.184 TWLQ98MeanElevation The temporal mean of the 98% quantile total water level elevation across the time series, in meters NAVD88. Null values represent bins where no total water level information existed within 1 km of the bin. This condition existed for only one of the 987 bins. USGS 1.587 3.732 TWLQ98MeanElevationUncertaint 95% confidence interval describing uncertainty of the 98% quantile total water level elevation mean, in meters. Null values represent bins where no total water level information existed within 1 km of the bin. This condition existed for only one of the 987 bins. USGS 0.042 0.119 TWLQ98FinalElevationPredictio Predicted 98% quantile total water level elevation at the end of the TWL time series (12/31/2018), in meters NAVD88. This is represented by either a regression prediction or a time series mean. See the Vertical_Positional_Accuracy_Report section of this metadata for more information. Null values represent bins where no total water level information existed within 1 km of the bin. This condition existed for only one of the 987 bins. USGS 1.587 4.024 TWLQ98FinalElevationUncertain Uncertainty for the final predicted 98% quantile total water level elevation, in meters. This is represented by either a prediction interval or a confidence interval. See the Vertical_Positional_Accuracy_Report in this metadata for more information. Null values represent bins where no total water level information existed within 1 km of the bin. This condition existed for only one of the 987 bins. USGS 0.046 1.243 ElevDiff_FinDuneElevAndTWLQ98 The vertical difference between the final predicted dune crest elevation at the end of the time series and the final predicted 98% quantile total water level elevation, in meters. Negative values indicate that the final predicted 98% quantile total water level elevation was higher than the final predicted dune crest elevation. Null values represent bins where no total water level information existed within 1 km of the bin. This condition existed for only one of the 987 bins. USGS -1.571 7.444 SurveyRange String recording the date of the first and last survey of the time series with valid dune crest data at this location. USGS The month, day, and year (MM/DD/YYYY) of the first and last survey in the time series, separated by a hyphen. XCoord Easting (x) coordinate (WGS 84 UTM 18N). USGS 172289.1866 458262.4674 YCoord Northing (y) coordinate (WGS 84 UTM 18N). USGS 3748925.4136 4044873.0271 NC_Dune_Condition_Codes_Time_Series_Map_Pack.mpkx: ArcGIS Pro Map Package containing the dune condition codes (NC_Dune_Condition_Codes) and time series features (NC_Time_Series_Features) feature classes, stored inside a file geodatabase (NC_Dune_Condition_Codes_Time_Series.gdb). The Map Package also contains the Hybrid Reference Layer and World Imagery basemaps published by Esri in the Living Atlas. These basemaps are accessible via ArcGIS Online: Hybrid Reference Layer (https://www.arcgis.com/home/item.html?id=30d6b8271e1849cd9c3042060001f425) and World Imagery (https://services.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer). Scatterplots in the map pack are designed to only display plots from singular condition code points selected by the user. The user must bandbox select a desired condition code point with the Select interactive tool for a scatterplot to display data. The entity and attribute information were generated by the individual and/or agency identified originator of the dataset. Please review the metadata records associated with this data release for additional details and information. U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center USGS SPCMSC Data Management mailing and physical

600 4th Street South

Saint Petersburg FL 33701 United States 727-502-8000 gs-g-spcmsc_data_inquiries@usgs.gov NC_Dune_Condition_Codes_GDB.gdb, NC_Dune_Condition_Codes_ASCII.csv, NC_Dune_Condition_Codes_Time_Series_Map_Pack.mpkx This digital publication was prepared by an agency of the United States Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. comma-delimited text, file geodatabase (Esri), ArcGIS Pro Map Package ArcGIS Pro 3.0.3 The data download file is compressed and must be unzipped using software such as WinZip, 7Zip, etc. before use. https://coastal.er.usgs.gov/data-release/doi-P9WYA19U/data/NC_Dune_Condition_Codes_Time_Series.zip None The geodatabase feature class and ArcGIS Map Package were created for the use within Esri ArcGIS Pro software (3.0.3 or newer). The ASCII table data were created for the use within Microsoft Excel, or similar text viewers, such as Notepad. 20260310 U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center USGS SPCMSC Data Management mailing and physical

600 4th Street South

Saint Petersburg FL 33701 United States 727-502-8000 gs-g-spcmsc_data_inquiries@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 local time