Date of Graduation


Document Type


Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level



Civil Engineering


Richard A. Coffman

Committee Member

Michelle Bernhardt

Second Committee Member

Kristofor Brye

Third Committee Member

Norman Dennis, Jr.

Fourth Committee Member

Jason Tullis


Biological sciences, Applied sciences, Earth sciences, Proximal sensing, Remote sensing, Soil water characteristic curve, Unsaturated soils


A multiband system including active microwave sensing and visible-near infrared reflectance spectroscopy was developed to measure unsaturated soil properties in both field and laboratory environments. Remote measurements of soil volumetric water content (θv), soil water matric potential (ψ), and soil index properties (liquid limit [LL], plastic limit [PL], and clay fraction [CF]) were conducted. Field-based measurement of θv was conducted using a ground-based radar system and field measurements within 10 percentage points of measurements acquired with traditional sampling techniques were obtained. Laboratory-based, visible and near infrared spectroscopy was found to be capable of obtaining empirical, soil specific regression functions (partial least squares [PLS]) with coefficient of determination (R2) values greater than 0.9 for the LL, PL, and CF. A silt sized granite material, a silt sized illite clay, and a silt sized kaolinite clay were optically characterized within the visible to near-infrared wavelength range and were found to have absorption coefficient values of 0.81 to 78.8cm-1, 0.93 to 150.0cm-1, and 0.12 to 4.02cm-1, respectively.

Measurements of θv and ψ using an analytical solution based on the Kubelka-Munk color theory were found not to provide viable results. Soil water characteristic curves (SWCC) were fitted to both laboratory-obtained and remotely-sensed data between -10 and -1500kPa. θv for the laboratory-obtained SWCC (SWCC-L) and remotely-obtained SWCC (SWCC-R) for the granite silt were within 1 percentage points for ψ values less than -100kPa. The SWCC-L and SWCC-R values for the silt sized illite clay were within 2 percentage points for values of ψ greater than 400kPa. The SWCC-L and SWCC-R for the silt sized kaolinite clay were within 8 percentage points for all ψ values. For the Donna Fill and illite soil types ψ values within 150kPa of the applied pressure were obtained.

Specific contributions of this research project were the evaluation of remote and proximal (active microwave and diffuse reflectance spectroscopy) sensing techniques as a means of acquiring measurements of soil properties. Microwave measurements of field θv were demonstrated for ground based systems. Additional areas of research in both laboratory- and field-scale measurements of soil hydraulic and index properties are identified and discussed.