Abstract
Mapping wetlands with high spatial and thematic accuracy is crucial for the management and monitoring of these important ecosystems. Wetland maps in New Brunswick (NB) have traditionally been produced by the visual interpretation of aerial photographs. In this study, we used an alternative method to produce a wetland map for southern New Brunswick, Canada, by classifying a combination of Landsat 8 OLI, ALOS-1 PALSAR, Sentinel-1, and LiDAR-derived topographic metrics with the Random Forests (RF) classifier. The images were acquired in three seasons (spring, summer, and fall) with different water levels and during leaf-off/on periods. The resulting map has eleven wetland classes (open bog, shrub bog, treed bog, open fen, shrub fen, freshwater marsh, coastal marsh, shrub marsh, shrub wetland, forested wetland, and aquatic bed) plus various non-wetland classes. We achieved an overall accuracy classification of 97.67%. We compared 951 in-situ validation sites to the classified image and both the 2106 and 2019 reference maps available through Service New Brunswick. Both reference maps were produced by photo-interpretation of RGB-NIR digital aerial photographs, but the 2019 NB reference also included information from LiDAR-derived surface and ecological metrics. Of these 951 sites, 94.95% were correctly identified on the classified image, while only 63.30% and 80.02% of these sites were correctly identified on the 2016 and 2019 NB reference maps, respectively. If only the 489 wetland validation sites were considered, 96.93% of the sites were correctly identified as a wetland on the classified image, while only 58.69% and 62.17% of the sites were correctly identified as a wetland on the 2016 and 2019 NB reference maps, respectively.
Highlights
Wetlands are defined as lands that are saturated with water long enough to cause the formation of hydric soils and the growth of hydrophytic or water-tolerant plants [1]
Following [73], they were defined as a wetland when the water table was close to or at the surface, or when we found indicator plants, soil hydrology, or other signs that the area is very often saturated with water
We achieved an overall accuracy (OA) of 97.67% indicating an excellent classification accuracy
Summary
Wetlands are defined as lands that are saturated with water long enough to cause the formation of hydric soils and the growth of hydrophytic or water-tolerant plants [1]. Wetlands are found in almost all the regions of the world from the tundra to the tropics and are a critical part of the natural environment [2,3]. They have high biological diversity and offer critical habitats for numerous flora and fauna species [3]. Wetlands are complex ecological systems that are formed when hydrological, geomorphological, and biological factors work collectively to create the necessary conditions [4]. There are various types of wetlands depending on the regional and local variations in soils, topography, climate, hydrology, water chemistry, vegetation, and other factors, including human disturbances [5,6]
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