Coastal wetland mapping combining multi-date SAR and LiDAR

Abstract

Inventorying and monitoring are imperative to management of vulnerable coastal wetlands. Multi-date and multi-sensor remote sensing offer new capabilities to wetland programmes such as the US National Wetland Inventory. This pilot study focuses on swamp forests and pocosins, marshes, shrub–scrub and invasive Phragmites australis. Combinations of spaceborne multi-date Synthetic Aperture Radar (SAR) imagery and airborne light detection and ranging (LiDAR) elevation (bare earth elevation and vegetation height) were evaluated. Multi-date SAR data (horizontal-horizontal and horizontal-vertical dual polarizations) highlighted physiognomic dynamics, with LiDAR vegetation canopy discerning selected classes. The highest overall accuracy used SAR, LiDAR canopy and digital elevation model (DEM) data (81% κ = 0.744), but not significantly different from the SAR-only classification (81% κ = 0.742). Both classifications exceeded the data combination using SAR data and DEM (66% κ = 0.521) and SAR data with vegetation canopy (80% κ = 0.725). This approach requires investigation using advanced classification algorithms to prove its potential for monitoring wetland change, sea-level rise, and invasive species.

Keywords:

• coastal wetlands
• light detection and ranging (LiDAR)
• National Wetland Inventory
• Synthetic Aperture Radar (SAR)

Acknowledgements

Two anonymous reviewers provided critiques to greatly improve the manuscript and further research. The US Fish and Wildlife Service National Wetland Inventory (NWI) program provided grant support via Cooperative Ecosystems Studies Unit (CESU) agreement F10AC00365. Mr John Swords and Doug Newcomb provided tangible advice, data and vital field assistance. Dr Brian Boutin of The Nature Conservancy provided access and valuable advice on ecological processes and management activities in the vicinity of Alligator River field sites.