Soil erosion on the Canadian Interior Plains is an economic and environmental problem which threatens the sustainability of annual crop production. The conventional approach to regional assessment of erosion risk is the interpretation of soil maps and evaluation of empirical soil loss equations. Use of pre-existing spatial units (quarter-sections, fields, soil map units) simplifies data storage and management, but produces very approximate models of soil landscapes, lacking the spatial resolution of the original maps. Furthermore, a dichotomy exists between the scale of erosional processes and the size of spatial unit in a typical regional study. Parameter values averaged over heterogeneous map units represent a misuse of process models derived from plot-scale experiments. This paper describes the use of a geographic information system (GIS) to model glacial landscapes and evaluate relative erosion risk at a sub-field scale over large areas. When soil and geological surveys, land cover data, and digital elevation models are combined in a GIS, landscapes can be stratified according to the dominant controls on wind and water erosion. This approach ensures geographic integrity and the best soil loss estimates with available data. Maximum use of digital geologic surveys awaits the availability of the three-dimensional GIS.