DOI: 10.5061/dryad.41ns1rnj6
title: Data for: Barnegat Bay (NJ) salt marsh extent 1995 and 2015

description: We provide salt marsh delineations for Barnegat Bay, New Jersey, by means
 of object-based image analysis of high-resolution aerial imagery and
 digital elevation models. We performed trends analyses of salt marsh
 extent from 1995 to 2015 and estimated drivers of marsh area change. We
 found that in 1995, 8,830 ± 390 ha were covered with marsh vegetation,
 while in 2015 only 8,180 ± 380 ha of salt marsh habitat remained.
description: Data for the classification of coastal land-cover of Barnegat Bay
 were downloaded from the USGS Earth Resources Observation and Science
 (EROS) Center via the USGS Earth Explorer website. The spatial data
 comprised high-resolution orthoimages acquired in April 1995
 (color-infrared, 3 bands, 1 m resolution) and April 2015 (4 bands, red,
 green, blue, near-infrared, 0.3 m resolution), as well as a bathymetric
 model from 2000 (10 m resolution) and a digital elevation model (DEM) from
 2015 (1 m resolution). Digital elevation models were clipped to the area
 of interest and resampled to 1-m cell size in ArcMap 10.2.2 (Esri, West
 Redlands, CA, USA). Aerial imagery orthomosaics were clipped to the same
 extent and fused with the DEMs to generate a five-band raster file for
 2015 (red, green, blue, near-infrared, elevation; 1-m cell size) and a
 four-band raster file for 1995 (red and near-infrared combined in band 1,
 1-m cell size). These raster files were imported into eCognition Developer
 9 (Trimble, Sunnyvale, CA, USA) for object-based image analysis. After
 spectral-difference and multi-resolution segmentation, a supervised
 classification process was used to assign each image object to the classes
 ‘Open Water,’ ‘Upland,’ ‘Salt Marsh,’ or ‘Unvegetated’. Class assignment
 was based on object mean values for bands 1 to 5, maximum difference, hue,
 or brightness via hierarchical decision trees. Obvious classification
 errors were manually corrected before classification results were exported
 as raster files. A change map was generated from the 1995 and 2015
 classifications, assigning cells to the four classes of marsh loss, marsh
 gain, stable non-marsh, and stable marsh. To estimate
 the total area of change classes with confidence intervals, a reference
 dataset of 1600 points was allocated to the four change classes in a
 stratified random design. Labeling of the reference dataset used higher
 resolution imagery, where available. In addition, drivers of changes in
 Barnegat Bay salt marsh extent were annotated using the classes ‘edge
 erosion’, ‘ponding’, ‘mosquito control’, and ‘channel widening’ for
 conversions of marsh to non-marsh, as well as ‘upland migration’, ‘pond
 revegetation’, and ‘bare revegetation’ for conversions of non-marsh to
 marsh.
description: Files are provided as raster in .tiff format (8 bit).
 Classes are defined as follows: 1995.tif,
 2015.tif: 1-Open Water; 2-Upland; 3-Salt Marsh; 4-Unvegetated
 Trend.tif: 1-Stable non-marsh; 2-Stable marsh; 3-Marsh gain;
 4-Marsh loss   Ground-control points
 are provided in .csv format. Classes are defined as
 follows: Control_points.csv: M-Marsh;
 U-Unvegetated