ABSTRACT: Estimating snow volume in the Elbow River Watershed using Airborne Lidar.

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In this research snow pack modeling was attempted in the Elbow River watershed, west of Calgary, Alberta using lidar derived elevation data. The City of Calgary and the Department of Sustainable Resources Development (SRD) were interested in determining whether a winter and a summer lidar dataset can be used to estimate the mean snow depth. Lidar is an airborne laser system that calculates the distance to the ground by determining the return time of emitted laser pulses spatially located by a survey grade global positioning system (GPS) and an inertial motion unit (IMU). Subtraction (Digital Elevation Model (DEM) change detection) of the summer dataset from the winter dataset provides a snow depth dataset that is used to determine mean snow depth. Mean snow depth and an average field-measured snow densities were used to calculate snow water equivalent (SWE). An estimate of snow volume was determined using three methods, 1) one mean snow depth, 2) four terrain attributes (slope, aspect, elevation, and canopy fractional cover) individually and 3) a multiple terrain attribute GIS approach. Application of an average snow depth (3.4 x 107m3) rendered a similar approximate value for snow water equivalent for the study site as the results from slope (3.6 x 107m3), aspect (3.5 x 107m3) and canopy fractional cover (3.5 x 107m3) terrain attributes. Elevation (4.2 x 107m3) and the GIS model (4.3 x 107m3) gave higher estimates of snow water equivalent in the Elbow River watershed since elevation plays a strong role in snow accumulation. Future research should include validation of lidar runoff values with stream gauge data; as well re-evaluating the methods proposed in an area of greater snow depth (the average snow depth in the Elbow River watershed was 18cm, which is the accuracy limit of current lidar systems). Preliminary results indicate that the use of lidar to estimate snow depth is viable option for the determination of snow depth in a mountainous region. Application of this research can be used in conjunction with current water resource management strategies to assist in prediction of seasonal runoff volumes. The advancement of water volume prediction for watersheds can aid city planners with regulating water supply as well as prepare for flooding events.

Bibliography of Canadian Geomorphology