Estuarine Shoreline and Barrier-Island Sandline Change Assessment Dataset

Transects were generated at a 50-meter interval perpendicular to the baseline for both the Assateague Island MD/VA and the New Jersey study areas. The shorelines were split into two different analysis groups: (1) 1800s-2013 and (2) Pre/Post Hurricane Sandy. Rates of change were calculated for: (1) net shoreline movement (NSM) (2) linear regression rate (LRR) for the foreshore, backshore, and sandline and saved to a table, in the ArcGIS personal geodatabase format. The LRR was calculated for only the 1800s to 2013 datasets, while the NSM was calculated for only the Pre/Post Hurricane Sandy Datasets. The rate table generated by DSAS was then joined to the respective transect file so the rate values could be displayed on a map.

Barrier width: the width (m) of the island from the beach shoreline to the bay-side shoreline. The width was determined by intersecting shoreline data digitized from the latest pre-Sandy ortho-rectified natural color imagery, provided by the National Agricultural Imagery Program (NAIP), with the DSAS transects. Imagery was collected in May 2012 and June 2011 for Virginia and Maryland, respectively. To obtain island width, transects were clipped by both the front and back shorelines in ArcGIS and the remaining length was tabulated. The corresponding field is Island_Wid. Barrier height: maximum vertical height (m) calculated from pre-Sandy lidar data collected in March 2010. Clipped transects from barrier width analyses were attributed with spatially coincident lidar elevation using the "Add Surface Information" tool in ArcGIS 3D Analyst extension, which added the Z_MAX, Z_MEAN, and Z_MIN properties to the transect attribute table. The corresponding fields are Z_Min, Z_Max, and Z_Mean.

Estuary width: the width (m) of the estuary from the the back barrier shoreline to the closest land (mainland or other island) shoreline. The width was determined by intersecting shoreline data digitized from the latest pre-Sandy ortho-rectified natural color imagery from NAIP with the DSAS transects. Imagery was collected in May 2012 and June 2011 for Virginia and Maryland, respectively. To obtain estuary width, transects were clipped by both the back barrier and mainland (or nearby island) shorelines in ArcGIS and length tabulated. The corresponding field is Estuary_Width. Estuary depth: the maximum depth of the estuary (m). Data on estuarine bathymetry were obtained from the Ocean City digital elevation model (DEM) published by the National Oceanic and Atmospheric Administration (NOAA). The corresponding fields are Bathy_Min, Bathy_Max, and Bathy_Mean. Hurricane Sandy maximum wave height for ocean and estuary: maximum wave height (m) from Hurricane Sandy were calculated from hydrological models. Model output was imported into ArcGIS using the centroid coordinates for each model grid cell. A spatial join, with a distance of 500 meters, calculated the average maximum wave height for cells within 500 meters of each island transect. Corresponding fields are Bay_Waves_Mean, Bay_Waves_Max, Beach_Waves_Mean, and Beach_Waves_Max.

For hydrodynamic data (Surge, Setup, Runup, TWL): Water level was computed in Matlab (version R2013b) by adding storm surge from NOAAs Psurge model to wave setup and runup. The wave height and period for calculating wave runup and setup come from the Wavewatch III model. Hydrodynamic parameters were calculated in Matlab and exported into ArcGIS format. For details on modeling parameterization, see: Stockdon, H.F., Doran, K.J., Thompson, D.M., Sopkin, K.L., Plant, N.G., and Sallenger, A.H., 2012, National assessment of hurricane-induced coastal erosion hazards: Gulf of Mexico: U.S. Geological Survey Open-File Report 2012-1084, 51 p. http://pubs.usgs.gov/of/2012/1084/

The data from the various analyses were spatially joined into a new transect shapefile for each of the two study areas. As this file was generated inside of an ArcGIS personal geodatabase it was converted to an excel spreadsheet and any "NULL" values were changed to "-99999" for publication purposes. The final products are Excel and comma separated values (csv) files for Assateague Island and another for the New Jersey coast.

Added keywords section with USGS persistent identifier as theme keyword.