Digital Shoreline Analysis System version 4.3 Transects with Short-Term Linear Regression Rate Calculations for South Carolina (SC)

Transect features generated using DSAS v4.3 in ArcMap v10. Parameters Used: baseline layer=SC_baseline, baseline group field=NULL, transect spacing=50 meters, transect length=4000 meters, cast direction=AUTO-DETECT, baseline location=offshore, cast method=smoothed, smoothing distance=7000 meters, flip baselines=not selected. For additional details on these parameters, please see the DSAS help file distributed with the DSAS software, or visit the website at: https://woodshole.er.usgs.gov/project-pages/DSAS/version4/ This process step and all subsequent process steps were performed by the same person: M.G. Kratzmann.

Some transects were manually edited for length, moved, or deleted in an edit session using standard editing tools in ArcMap v10.

Rate calculations performed in DSAS v4.3 using ArcMap v10 on selected shoreline features only (Select by Attributes, [Year]>=1960) with the following criteria: 1) they contained three or more shorelines required to compute short-term linear regression shoreline change analysis (a shoreline from the 1960s-70s, the modern (lidar-derived or 1990s) shoreline, and at least one other shoreline from the 1960s to present); 2) they contained the two minimum shorelines required to compute short-term end point shoreline change analysis (a shoreline from the 1960s-70s and the modern (lidar-derived or 1990s) shoreline). In South Carolina, the shoreline date range for short-term linear regression rates is 1962 to 2000. Shoreline uncertainty table added to ArcMap project (SC_shorelines_uncertainty.dbf) and used by DSAS to apply bias-correction to distance measurements established by transects. Parameters Used: shoreline layer=SC_shorelines (selected features), shoreline date field=Date_, shoreline uncertainty field name=Uncy, the default uncertainty=5.1 meters, shoreline intersection parameters=closest, stats calculations=[End Point Rate (EPR)], [Linear Regression Rate (LRR)], shoreline threshold=2, confidence interval=90%, Output rate table name=transects_SC_rates_20131107_102958.

Shoreline rates table (transects_SC_rates_20131107_102958.dbf) was joined to the transect feature class in ArcMap v10 by right-clicking on the transect layer > joins and relates > join > join attributes from a table. Parameters: join field - OBJECTID; table to join - transects_SC_rates_20131107_102958; field in table: TransectID; join options - keep only matching records.

Transects containing linear regression rates in the joined feature class were selected and exported to a shapefile (SC_transects_rates_STlrr.shp) in ArcMap v10 by right-clicking the transect layer > data > export data, permanently linking the joined rate fields to the transects. Superfluous fields in the linear regression rates shapefile pertaining to the end point rate method were deleted. Linear regression rates are reported with preference when both rate types exist for a given transect.

The short-term linear regression rate transects were visually compared with the short-term end point rate transects in an ArcMap session. Each set of transects was assigned a different color and the short-term linear regression rate transects were manually deleted for any stretch of alongshore coast that had fewer than 90% coverage for a 1 kilometer stretch (18 or more transects out of 20 for 50-meter spacing).

Any transects that did not cross the lidar shoreline were deleted using standard editing tools in ArcMap v10.

The edited short-term linear regression rate transect shapefile was projected in Esri's ArcToolbox (v10.2) > Data Management Tools > Projections and Transformations > Project. Parameters: input projection - UTM zone 17N (WGS 84); output projection - geographic coordinates (WGS 84); transformation = none.

Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog.

Added keywords section with USGS persistent identifier as theme keyword.