Modeling Hydraulic Properties and Hydrologic Processes in Shrink-swell Clay Soils

Thursday, 17 December 2015: 10:35
3018 (Moscone West)
Ryan D. Stewart1, David E Rupp2, Majdi R Abou Najm3 and John Steven Selker2, (1)Virginia Polytechnic Institute and State University, Blacksburg, VA, United States, (2)Oregon State University, Corvallis, OR, United States, (3)American University of Beirut, Beirut, 1107, Lebanon
Recognizing the need for tractable models that accurately describe the hydrologic behaviors of shrink-swell soils, we propose a new conceptual model that identifies up to five porosity domains based on morphological and hydrological distinctions. We provide governing equations that predict the porosity distribution as a function of soil water content and six additional parameters, all of which can be determined using laboratory measurements conducted on individual soil samples. We next derive new expressions for the hydraulic properties of such soils, which can be used to model infiltration at the plot scale. Finally, we incorporate these expressions into new models that can be used to predict and quantify surface runoff (i.e., overland flow) thresholds, and which may be used to reveal the dominant mechanisms by which water moves through clayey soils. Altogether, these models successfully link small-scale shrinkage/swelling behaviors with large-scale processes, and can be applied to such practical applications as converting measurements between gravimetric and volumetric water contents, as well as to predicting field-scale processes such as the sealing of individual cracks.