Spatiotemporal variation in Oregon salt marsh expansion and contraction

The dataset is a layer file created in ArcGIS Pro 2.2. The dataset includes digitized outlines of the seaward edges of five Oregon salt marshes (Nehalem, Netarts, Salmon, Alsea, and Coquille). These are roughly decadal from 1939 to 2018 and were hand-digitized using historical aerial photography (1939 to the late 1990s) scanned at the University of Oregon’s Map & Aerial Photography Library and aerial imagery downloaded from the Oregon Statewide Imagery Program (https://www.oregon.gov/geo/Pages/imagery_data.aspx). Historical aerial imagery were georeferenced using ≥ 10 control points that were placed at stable locations including road and channel intersections, and using a second order polynomial transformation. Salt marsh areas were determined using a stable upslope edge (Pacific Marine & Estuarine Fish Habitat Partnership current extent map https://www.pacificfishhabitat.org/data/). The dataset also includes rates of salt marsh seaward edge change which was calculated using the USGS Digital Shoreline Analysis System (DSAS; https://www.usgs.gov/centers/whcmsc/science/digital-shoreline-analysis-system-dsas?qt-science_center_objects=0#qt-science_center_objects) in ArcMap 10.7.1 over roughly decadal periods from 1939 to 2018 and integrated over the period of record. DSAS automatically placed transects at 5 m intervals perpendicular to digitized marsh edges. When calculating the rate of edge change integrated over all digitized edges, regressions were fit for any transect that passed through ≥ 6 edges. Error estimates associated with the regressions were calculated with 95% confidence intervals. These rates and uncertainties can be found in the attribute tables of each shapefile.