Topographic LiDAR – providing a new perspective in the Mackenzie Delta

Topographic LiDAR is used to map flooding hazards along the Beaufort Sea coast, in particular on the outer Mackenzie Delta. Flooding can be caused by storm surges anywhere along the coast and by high river discharge or backwater at spring breakup or later in summer and fall on the delta. Airborne scanning laser altimetry using LiDAR enables the generation of geospatial information with decimetre level resolution in the form of digital elevation models (DEMs) representing the ground surface, digital surface models (DSMs) including trees and structures, and signal intensity returns to represent the surficial features and materials. LiDAR data are ideal for feature recognition and quantification, providing small-scale geomorphological and depositional details within a larger-scale context. The identification and formation of coastal and river levees, crevasses, secondary channels, and floodplain topography can be useful in determining flooding thresholds, inundation pathways, and drainage patterns. Indicators of past flooding events such as lines of driftwood debris, dead vegetation patterns and the accumulation of alluvial material inland can also be detected through the topographic LiDAR data. Due to the relatively flat nature of much of the low-lying modern Mackenzie Delta, slight increases in water levels can produce extensive additional flooding inland. Flood-simulation models based on LiDAR DEMs can show the potential for inland flooding for a given storm-surge water level at the coast.