Abstract
Riparian vegetation delineation includes both the process of delineating the riparian zone and classifying vegetation within that zone. We developed a holistic framework to assess riparian vegetation delineation that includes evaluating channel boundary delineation accuracy using a combination of pixel- and object-based metrics. We also identified how stream order, riparian zone width, riparian land use, and image shadow influenced the accuracy of delineation and classification. We tested the framework by evaluating vegetation vs. non-vegetation riparian zone maps produced by applying random forest classification to aerial photographs with a 1 m pixel size. We assessed accuracy of the riparian vegetation classification and channel boundary delineation for two rivers in the northeastern United States. Overall accuracy for the channel boundary delineation was generally above 80% for both sites, while object-based accuracy revealed that 50% of delineated channel was less than 5 m away from the reference channel. Stream order affected channel boundary delineation accuracy while land use and image shadows influenced riparian vegetation classification accuracy; riparian zone width had little impact on observed accuracy. The holistic approach to quantification of accuracy that considers both channel boundary delineation and vegetation classification developed in this study provides an important tool to inform riparian management.
Highlights
Riparian floodplain vegetation is a landscape feature with ecological importance that often far exceeds its spatial extent [1] as it provides unique habitat for many wildlife species and corridors for species migration [2]
This study used a semi-automatic approach to delineate river channel boundaries and classify riparian vegetation using a freely available public dataset (NAIP) and cloud-based technology (Google Earth Engine)
The subsequent evaluation holistically quantified the accuracy of riparian vegetation delineation by including assessment of both channel boundary and riparian classification accuracy and demonstrated that both elements are critical in terms of comprehensively understanding the quality of riparian vegetation maps
Summary
Riparian floodplain vegetation is a landscape feature with ecological importance that often far exceeds its spatial extent [1] as it provides unique habitat for many wildlife species and corridors for species migration [2]. Over the last few decades, the increased availability of imagery with a range of spatial resolutions, as well as derived land cover mapping products (e.g., the National Land Cover Dataset), have enhanced the capacity to detect and delineate riparian vegetation coverage, species, and communities over large extents [5,6,7,8,9]. Despite these advancements, we still lack comprehensive maps of the location and condition of riparian plant communities [10].
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