THE APPLICATION OF HIGH RESOLUTION LIDAR ELEVATION DATA FOR MAPPING GEOLOGICAL LANDFORMS AND WATERSHEDS

In the summer of 2000 a section of the Annapolis Valley, Nova Scotia was selected for a high-resolution elevation campaign. LIDAR, Light Detection And Ranging, is a technology that involves firing a laser pulse from an aircraft toward the ground to measure the ground elevation. The laser beam allows the ground beneath the tree canopy to be imaged and a “bald-earth” surface can be interpolated between the ground points. The footprint of the laser beam was approximately 15 cm in diameter with a ground spacing of laser hits ranging from between 2 m for open areas to around 5 m under the vegetation canopy. The system also allows for very accurate height determinations, on the order of 15 cm in the vertical. The resultant Digital Elevation Model (DEM) can be shaded and colourized to allow interpretation of both bedrock and surficial geological landforms. The North Mountain Basalt of the Mesozoic Fundy Basin is comprised of three flow units with different characteristics. The lower flow unit has very few vesicles or amygdule, has a massive texture with well-developed columnar joints, and is resistant to erosion. The lower flow unit is exposed along the northern slope of the Annapolis Valley. This middle flow unit overlays the lower flow unit and has significant amounts of zeolite amygdules of potential economic grade. The vesicular nature of the basalt flows make this unit more subject to increased erosion. This unit is in turn overlain by the upper flow unit that has similar characteristics of the lower flow unit and outcrops along the Bay of Fundy coast. This study is evaluating the use of traditional ca 30 m and high resolution DEMs from LIDAR to map the three flow units based on their topographic expression. Several landforms related to surficial material have also been identified including raised beach deposits and glacial features (drumlins, deltas, etc.). Another potential benefit from the higher resolution DEM from LIDAR is in the area of hydrology and defining watersheds from DEMs. The area is known to have poor water quality, possibly related to agricultural landuse. Watersheds generated from a 20 m DEM will be compared with those derived from LIDAR. These data will be used in turn to examine the relationship between landuse and drainage basins of different scales.