GSA 2020 Connects Online

Paper No. 143-13
Presentation Time: 4:50 PM

PALAEOHYDRAULIC RECONSTRUCTION OF GLACIAL LAKE EDMONTON, ALBERTA, CANADA


RUBIN, Allison Denise, Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, AB T6G2E3, Canada, NORRIS, Sophie Louise, Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, AB T6G 2E3, Canada; Earth Sciences, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H4R2, Canada and FROESE, Duane G., Department of Earth and Atmospheric Sciences, University of Alberta, 116 St & 85 Ave, Edmonton, AB T63 2RG, Canada

Glacial Lake Edmonton was a short-lived proglacial lake that formed in central Alberta as the Laurentide Ice Sheet’s southwestern margin retreated. Although this lake considerably altered the geomorphology of the region, there is a scarcity of research relating to its genesis and the palaeohydraulics of its drainage. This study uses high resolution LiDAR imagery to identify the geomorphic features and reconstruct lake evolution. We identify five stages of lake evolution, the most extensive of which drained catastrophically through the previously identified Gwynne outlet. We use a HEC-GeoRAS/HEC-RAS system along with palaeo-depth indicators to estimate the water surface elevation and palaeo-bed topography of the main Gwynne outlet. We then use previously derived associations between lake volume and peak discharge and compare the results with peak discharges derived from spillway incision. Adjusting for downstream attenuation, results from both methods are concordant. We suggest the most extensive Gwynne stage, covering ~3500 km2 with an outburst volume of 44 km3, had an estimated peak discharge of 25,000 - 95,000 m3 sec-1 and a minimum flow duration of 5-8 days. These data, coupled with a lack of outburst depositional features, suggest sediment supply is a major control on spillway morphology within the Canadian Prairies.