Description: The Geospatial Laboratory for Soil Informatics at Iowa State University created this spatial dataset, combining science and art to provide a unified perspective on the landscape, integrating geology, landforms, soil, water systems, and vegetation. To create the Physiographic Subregions Map of Iowa, multiple lines of evidence were synthesized to delineate areas with similar landforms, geologic histories, soil characteristics, and hydrologic patterns. However, delineations were first created by evaluating patterns observed in terrain derivatives calculated from LiDAR-based elevation data (IDNR, 2020). Interpretation of those areas was then made in consideration of a compilation of foundational maps - including the Outline Map of the Drift Sheets of Iowa (Calvin, 1904), Soils of Iowa (Brown, 1936), Principal Soil Associations (Simonson et al., 1952), Principal Soil Association Areas of Iowa (1965), Quaternary Geology of Iowa (Ruhe, 1969), Principal Soil-Association Areas of Iowa (Fenton et al., 1971), Landform Regions of Iowa (Prior, 1976), Iowa Soil Association Map (Iowa Agriculture and Home Economics Experiment Station, 1978), Highway Guide of Iowa Soil Associations ((Iowa Department of Agriculture and Land Stewardship et al., 2012), and Landform Regions of Iowa (Iowa Geological Survey, 2017). Newer maps carried the most weight.Terrain derivatives, including slope gradient, profile curvature, and relative elevation, were computed from the LiDAR-derived digital elevation model (DEM) and integrated with a digital hillslope position classification (Miller and Schaetzl, 2015). Areas within Iowa’s state boundary (IDNR, 2020) exhibiting similar topographic patterns were delineated and correlated with existing soil and landform knowledge. The naming of subregions utilized established nomenclature, first, and then referenced representative towns. Descriptive terms were added to subregion names based on relative relief. The delineated subregions were evaluated for their differentiation in terms of soil properties and hydrologic behavior. Spatial statistics were applied to summarize data from existing soils (NCSS, 2025), stream networks (IDNR, 2024), and land cover maps (USDA-NASS, 2024).These subregions were grouped into regions by similarity. Membership of these subregions in more generalized physiographic regions is provided as an attribute in this spatial data layer, as well as in a separate shapefile. Many of the attributes calculated for the subregions in this “IA_physiographic_subregions” shapefile were also calculated for the larger delineations in the “IA_physiographic_regions” shapefile.
Service Item Id: 279eb9321a9b4618adcc1930b8a1dbeb
Copyright Text: Authors: Bradley A. Miller (Associate Professor, Iowa State University) and C. Lee Burras (Morrill Professor, Iowa State University)
The Department of Agronomy at Iowa State University supplied the funding needed to create this map.
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