Friday, 14 July 2006
107-1

Correlation of Redoximorphic Features to Hydrology.

David L. Lindbo1, Erik D. Severson2, Gerren Lanier1, and Michael Vepraskas1. (1) Soil Science Dept, North Carolina State Univ, Raleigh, NC 27695-7619, (2) USDA-NRCS, Buchanan County Soil Survey, PO Box 817, Vansant, VA 24656

Redoximorphic features and their location in the soil are indicative of seasonal saturation. Such features are extensively considered in many land use decisions (wetland soils, waste disposal, construction, etc.). The general objective of this study is to define relationships between soil morphology and long term hydrology. Since it is generally impractical to monitor a site for more than a few years, long term hydrology (30+ years) is modeled for each soil in the study. This model data is then used to correlate specific redoximorphic features to duration of saturation. Monitored sites are located on the Lower Coastal Plain and Outer Banks regions of North Carolina. These sites were chosen to represent a range of soil types typical of the region. Automated recording water table level wells monitored a total of 60 plots in transects of clayey, fine loamy, and coarse loamy Aquic Hapludults to Aeric Paleaquults; and sandy Typic Udipsamments to Aquic Udipsamments; for 1 to 5 years. These water table and on-site rainfall data were used as input information for the hydrologic model DRAINMOD to independently predict 30-yr historic water table levels for each soil. Using long-term weather data, soil wetness conditions for each method were determined for each plot. In the clayey to coarse loamy soils 2 chroma redox depletions correlate to 14 – 24% annual saturation, 3 chroma redox depletions correlate to 12 – 23% annual saturation, and redox concentrations correlate to 5 – 15% annual saturation. In the sand soils redox concentrations also correlate to approximately 15% annual saturation but 2 chroma depletions correlate to approximately 80% annual saturation. The use of redox features in land use decisions needs to be adjusted to reflect the observation that they correlate to different durations of saturation depending on soil type.

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