High-Resolution Mapping of Wet Terrain within Discontinuous Permafrost using LiDAR Intensity

Surface hydrology is an important aspect of northern environments on account of the thermal influence of water on permafrost. In this study, we demonstrate the ability of light detection and ranging (LiDAR) to map wet terrain within an area of discontinuous permafrost adjacent to the Northwest Territories Highway 3, located west of Yellowknife, Canada. Wet terrain was identified from LiDAR intensity measurements beneath forest canopies and across vegetated surfaces, including peatlands, fens, flooded black spruce and birch forests, and terrain adjacent to the highway embankment. Surface water pathways representing hydrological connections between water bodies and wet terrain were also identified at locations otherwise indiscernible from optical imagery. Statistical separability between terrain types, and thus the ability to map them, was improved by integrating LiDAR all-return and bare-earth intensity with colour orthophotos. The average classification accuracy for wet terrain was 93 per cent. These results indicate that LiDAR intensity can be used for local-scale mapping of wet terrain, as required by northern engineers and scientists. Future integration of LiDAR intensity and elevation measurements may be used to assess changes in surface hydrological conditions impacting permafrost.