Project Number: 6408-12130-014-00
Project Type: Appropriated

Start Date: Jul 03, 2007
End Date: Jun 30, 2012

Objective:
Objectives are directed toward a better understanding of erosion and sedimentation processes of sediment transport, deposition, and containment in agricultural watersheds and reservoirs. The focus is on the development and evaluation of innovative acoustic and seismic measurement techniques as they may be applied to soil erosion, sedimentation processes, sediment accumulation in impoundment reservoirs, and the structural integrity of impoundment reservoir dams. The proposed research objectives are: (1) development of measurement and monitoring technologies for assessing the temporal evolution and spatial distribution of the mechanical, hydrological, and structural properties of soils that are significant to erosion and transport of soil in the upland watershed area; (2) development of measurement and monitoring technologies for determining the temporal and spatial distribution, variation, and evolution of both suspended and bedload sediments in fluvial environments; (3) initiate field and laboratory studies using acoustic technologies for spatial delineation and characterization of sediments in relatively shallow reservoirs upstream from flood control dams; and (4) develop acoustic and/or seismic methodologies for identifying piping failure or changes in the structural integrity of earthen dams.

Approach:
(1) Develop new knowledge of acoustic and seismic techniques to measure soil mechanical properties to characterize the structural nature and stability of the soil surface and subsurface layers by conducting a long-term survey using acoustic probes and nonlinear acoustic sensors to measure the variation of sound speed and the nonlinear parameter as functions of temperature, water content, soil water potential, depth, and time, study field compaction effects using these acoustic techniques. Develop a sound speed-based 3D tomography system to visualize the variation of subsurface soil properties. Develop methods for characterizing and mapping of the spatial distribution and thickness of sealing/crusting layers of surface soil using a laser Doppler vibrometer (LDV)-based acoustic technique and a surface acoustic wave (SAW) sensor method. Develop a functional prototype system for the detection and characterization of high-strength soil layers such as fragipan. (2) Advance the state-of-the-art in the use of multiple acoustic frequencies for extracting detailed concentration and particle-size distribution information using laboratory tests. Deploy low cost acoustic systems in stream cross sections, and investigate the use of passive acoustic techniques to characterize bedload transport through passive measurements of gravel and sand dune migration. (3) Characterize the relationships between acoustic attributes, such as acoustic velocity, absorption, and impedance of sediments, and sediment physical properties, such as bulk density, grain size distribution, and pore fluid concentrations and study the relevant physical properties of the impoundment sediments and their relationship to acoustic attributes based on laboratory experiments. Develop the use of high-resolution acoustic sub-bottom profiling systems for sediment delineation and characterization by developing complementary acoustic field techniques of mapping and characterizing sediment accumulations in small flood-control reservoirs. (4) Study and evaluate the usefulness of seismic refraction tomography techniques for delineating the internal structure of earthen dams through the use of field surveys.