Shallow Seismic Investigation of Hydrogeologic Problems in the Brazos River Alluvium, Texas A&M Plantation, Burleson County, Texas

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McBrayer, M.A.
Twenty-two shallow, reversed, seismic refraction profiles were conducted in the Brazos River floodplain to test the feasibility of using seismic methods to provide hydrogeologic information in this province. The specific objectives were to map the total and saturated thickness of the alluvial deposits and to outline gravel lenses within the alluvium. It was found that the water table was the only interface at which the acoustical properties of the deposits above and below changed sufficiently to be mapped by seismic methods. The alluvial deposits above the water transmitted compressional waves at an average velocity just greater than the velocity of sound in air. The saturated alluvial deposits transmitted seismic waves at an average velocity of slightly greater than the velocity of sound in water. The saturated alluvial deposits and the bedrock appear to have a continuous increase in velocity with depth rather than a significant change in acoustical characteristics. The seismic measurements in themselves could not delineate gravel lenses within the alluvium. However, the zones of greater permeability were indicated on the resulting contour map of the water table by the areas of gentle gradients. Zones of greater permeability in the alluvial deposits are probably gravel lenses. 
Texas Water Resources Institute 
Technical Report 
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