Physiographic Regions of Iowa (Shapefile)

The state of Iowa contains diverse landscapes, each with subtle but impactful differences in their physical characteristics. This data set builds on the previously established landform regions of Iowa (Prior, 2000). All boundaries have been refined based on spatial data sets that become available since Prior (2000). Most importantly, this data set introduces subregions that present their own unique characteristics in terms of topography and geologic material, which results in different soil properties. Primary data sets considered for identifying and delineating subregions were digital terrain derivatives calculated from Iowa’s 2009 LiDAR-based digital elevation model (3m resolution) and the National Cooperative Soil Survey’s gSSURGO geospatial database. Changes in topography were mostly identified through analysis of a hillshade terrain derivative and the digital hillslope position model (Miller and Schaetzl, 2015), which combines consideration of slope gradient, relative elevation, and profile curvature. Changes in topography frequently reflect changes in geologic material. Nonetheless, additional consideration was given to differences in soil parent material (Miller and Burras, 2015). After the subregions were established, zonal statics were applied to the digital terrain derivatives, gSSURGO soil map, and USDA Cropland Data Layer for land use. The zonal statistics were used to verify the uniqueness of the subregions and to provide summary information for map users.

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References

Miller, B.A. and C.L. Burras. 2015. Comparison of surficial geology maps based on soil survey and in depth geological survey. Soil Horizons 56(1). doi: 10.2136/sh14-05-0005.

Miller, B.A. and R.J. Schaetzl. 2015. Digital classification of hillslope position. Soil Science Society of America Journal 79(1):132-145. doi: 10.2136/sssaj2014.07.0287.

Prior, J.C. 2000. Landforms of Iowa. University of Iowa Press, Iowa City.

Soil Survey Staff. 2014. Gridded Soil Survey Geographic (gSSURGO). United States Department of Agriculture, Natural Resources Conservation Service. http://datagateway.nrcs.usda.gov

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