Pro essional zyxwvutsrqponm Geo rapher, zyxwvutsrqp 42(2), 1990, pp 170-181 zyxwvutsr Q lopyright 1890 by Association of American Geographers THE UTILITY OF SOIL SURVEYS TO ASSESS FLOODPLAIN SEDIMENT STORAGE IN SOUTHEASTERN MINNESOTA* Timothy Beach zyxw University zyxwvu of Wisconsin-Eau Claire zyxwv How useful are county soil surveys for estimating floodplain storage in fluvial sediment budgets? This paper compares data about accelerated sedimentation collected from field corings with information derived from three county soil surveys in southeastern Minnesota. Two soil surveys proved to be unsatisfactory data sources about historical alluvium, but another survey was a more accurate source for one drainage basin. Even this third soil survey would require calibration for use in a geographic information system, because it was only the survey’s maximum estimate that agreed with the field data. zyxwvu Key Words: accelerated sedimentation, soil surveys, sediment budgets. European settlement accelerated up- land erosion and valley aggradation in much of the Driftless Area of the upper Mississippi Valley and in other parts of the United States (Happ 1944; Costa 1975; Knox 1977; Lowrance et al. 1985; Trimble and Lund 1982). Yet, little work has fo- cused on this phenomenon in southeast- ern Minnesota and other parts of the up- per Mississippi Valley that have environments similar to southwestern Wisconsin. This study begins to remedy the lack of research on floodplain aggra- dation in southeastern Minnesota by as- sessing the utility of county soil surveys for description and mapping of postset- tlement alluvium in three counties. Soil Conservation Service county soil surveys are the most widely distributed information sources for studying soil and sediment storage in drainage basins. These surveys, if reliable, could aid research on accelerated erosion and sediment storage, and thus help elucidate regional denu- This research was funded in part by a Dissertation Fellowship from the Graduate School and by Summer Fellowships from the Geography Department, Uni- versity of Minnesota. I thank Philip Gersmehl, Dwight Brown, James Fitzsimmons, the reviewers, and the editors for valuable comments on earlier drafts of this paper. The Cartography Lab at the University of Min- nesota assisted with the illustrations. dation rates, drainage basin response to land uses, rates of soil development, and, indirectly, sediment pollution of water. Information on accelerated erosion is par- ticularly important because soil erosion is a major source for water pollution (Chang et al. 1982). Detailed county soil surveys are made up of soil reports and soil maps. The sur- vey reports describe the central concepts of soil series profiles, and the soil maps show the distribution of soil series types (US Department of Agriculture 1951).De- scriptions of soil series provide ranges of specific soil attributes. Two attributes de- scribed in many county soil surveys of the upper Mississippi Valley are erosion class and depth to buried soils. The buried soils are thought to represent the presettle- ment floodplain surface (Knox 1977; Trimble and Lund 1982; Magilligan 1985). The range of depths to these buried soils therefore indicates the range of thick- nesses of accumulated historical allu- vium. Estimates of the volumes of postset- tlement alluvium in map units with buried soils could indicate historical sediment production, sediment storage (Gersmehl 1987), and long-term stream sediment yields. Soil descriptions and maps are de- veloped from an unspecified number of soil examinations (US Department of Ag- riculture 1951), and thus may be variable 170