The Impervious Surface 2021 dataset is a collection of polygon features derived from Calgary Digital Aerial Survey mapping linework which have been determined as impervious. Impervious surfaces are defined as any material which will seal the soil surface, impede water infiltration, collect solar heat or deprive tree or vegetation roots of aeration. Impervious surfaces effect many aspects of our City, including storm run off volumes, pollutant concentrations and drainage. The City must understand and manage the amount of impervious surfaces carefully to ensure the ongoing health and vitality of the municipality and the environment. To learn more about other DAS products available, visit Digital Aerial Survey