USING DIGITAL TERRAIN ATTRIBUTES TO MAP SOIL PARENT MATERIAL IN THE ARKANSAS RIVER VALLEY

The demand for detailed soil maps that can be used for land management and modelling continues to increase. Due to the influence of parent material on soil properties, an accurate map of parent material distribution can be utilized to gain broad information about the soil-landscape and further separate landforms into distinct soils. This study investigates a rule-based approach to mapping using digital terrain attributes as a method for differentiating areas of residuum from depositional areas of hillslope sediment (i.e. pedisediment) at an 890 hectare USDA-ARS research center in the Arkansas River Valley. Several terrain attributes derived from a 5-m digital elevation model were evaluated for their ability to distinguish erosional residuum from depositional pedisediment based on expert knowledge of the area. Three of the terrain attributes were utilized to predict parent material distribution: topographic position index, multi-resolution valley bottom flatness, and vertical distance to channel network. The resulting map was validated by sampling 20 locations using a conditioned Latin hypercube sampling (cLHS) design. Seventy-five percent of cLHS locations were accurately mapped as either residuum or pedisediment. This study confirmed the feasibility of separating parent material using digital terrain attributes in a highly weathered landscape. In addition, the parent material map could be used as an input for development of a detailed digital soil map.