Terrain Attributes Aid Soil Mapping on Low-Relief Indiana Landscapes

A digital soil survey update map for Howard County, Indiana, is being made using relationships between terrain attributes and soil properties. A soil land inference model using fuzzy logic provides the mechanism whereby terrain/soil relationships are extended from areas of direct soil property observation to areas of terrain analysis alone. Knowledge mining from existing soil survey data supplements the work and helps to establish terrain-soil relationships. It has been generally assumed that terrain attributes lose relevance and utility with decreasing landscape relief, but this is not the case in this fairly flat landscape. The Topographical Wetness Index (TWI) shows a strong utility in distinguishing Mollisols from Alfisols in the county. The terrain attribute of Altitude Above Channel Network is useful for distinguishing soils neighboring major drainage networks. The newly updated soil survey will provide point numerical estimates for soil properties rather than numerical ranges of soil attributes provided in current polygon-based survey product.