Developing an urban geomodel for the Edmonton area: The first step in understanding the complexities of urban geology

The development of a novel urban three-dimensional geomodel for the City of Edmonton area was pursued to support the evaluation of whether local groundwater can be used as an alternative water source in the event of reduced supply from the North Saskatchewan River. An urban geomodel enables the examination of how near-surface sediments influence development projects and provides a robust foundation for ongoing hydrological and geotechnical assessments. The geomodel is the first high resolution three-dimensional lithostratigraphic interpretation of the area and is consistent with previous geological cross-sections with respect to geometry and stratigraphic resolution. We compiled subsurface data from different sources and types including wireline logs, water well lithologs and geotechnical borehole logs in a unified borehole dataset including 17,000 interpreted logs and 21,340 new stratigraphic picks, leading to the subdivision of Neogene-Quaternary sediments into five lithostratigraphic units including surface coarse grained, glaciolacustrine, delta, and basal coarse-grained sediments along with till. The units were modeled using geostatistical methods. We leveraged LiDAR data to significantly refine our surficial geological mapping and provide geological boundaries for outcropping units. Interpreted logs were incorporated in machine learning models to predictively delineate bedrock topography, and the probability of sandiness above the bedrock unconformity. The predictive models were integrated into the three-dimensional lithostratigraphic geomodel which enhanced the geometric accuracy of units in areas with lower data density. This work highlights the effectiveness of integrating advanced predictive modelling methods with traditional pick-based mapping techniques providing an approach that can be replicated in other urban centers. By leveraging this geomodel, the City of Edmonton can evaluate and develop innovative watershed management practices that promote sustainable resource use and adaptive strategies for future climate impacts. These insights are essential for addressing pressing challenges in water security and climate resilience, particularly in urban environments undergoing rapid development and environmental change.