Carolyn G. Olson and William Effland. USDA-NRCS, 14th and Independence Ave, Washington, DC 20013
Soil geomorphic studies require three investigative steps. These include a) knowledge of the surficial stratigraphy and parent materials, b) geomorphic surfaces defined in time and space and c) correlation of soil and sediment properties to the landscape features. During the twentieth century, illustration of these three aspects was largely confined to two-dimensional products such as graphs, stratigraphic sections, fence diagrams, and flat maps of geomorphic surfaces and landscape relief. These products provide significant information and for those well-trained in spatial relations, contain sufficient information to develop a conceptual model representative of the landscape and its subsurface.Today, we have access to a wide array of three-dimensional visualization products that provide interpretative information in a GIS-structured environment. Three-dimensional displays may provide additional critical information not immediately apparent or possible to examine in two-dimensional renderings of data. Geomorphometric analysis using digital elevation models (DEMs) and associated derivative products offers possibilities for quantitative description and characterization of soil geomorphic relationships. We will examine several locations in the central USA for which soil-geomorphic data are available within an area of a few 10's of kms. Using 30-meter DEMs, the most commonly available elevation data in the USA, we will establish more quantitative relationships between geomorphic surfaces, soils, and sediments. In instances where multiple scale DEMs are available, we will develop criteria to determine the most representative scales for different geomorphic investigations.