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Open-File Report 2013–1050

Prepared in cooperation with the U.S. Army Corps of Engineers Sacramento District

Characterization of Major Lithologic Units Underlying the Lower American River Using Water-Borne Continuous Resistivity Profiling, Sacramento, California, June 2008

By Lyndsay B. Ball and Andrew P. Teeple

Thumbnail of and link to report PDF (6.03 MB)Abstract

The levee system of the lower American River in Sacramento, California, is situated above a mixed lithology of alluvial deposits that range from clay to gravel. In addition, sand deposits related to hydraulic mining activities underlie the floodplain and are preferentially prone to scour during high-flow events. In contrast, sections of the American River channel have been observed to be scour resistant. In this study, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, explores the resistivity structure of the American River channel to characterize the extent and thickness of lithologic units that may impact the scour potential of the area. Likely lithologic structures are interpreted, but these interpretations are non-unique and cannot be directly related to scour potential. Additional geotechnical data would provide insightful data on the scour potential of certain lithologic units. Additional interpretation of the resistivity data with respect to these results may improve interpretations of lithology and scour potential throughout the American River channel and floodplain.

Resistivity data were collected in three profiles along the American River using a water-borne continuous resistivity profiling technique. After processing and modeling these data, inverted resistivity profiles were used to make interpretations about the extent and thickness of possible lithologic units. In general, an intermittent high-resistivity layer likely indicative of sand or gravel deposits extends to a depth of around 30 feet (9 meters) and is underlain by a consistent low-resistivity layer that likely indicates a high-clay content unit that extends below the depth of investigation (60 feet or 18 meters). Immediately upstream of the Watt Avenue Bridge, the high-resistivity layer is absent, and the low-resistivity layer extends to the surface where a scour-resistant layer has been previously observed in the river bed.

First posted June 19, 2013

For additional information contact:
Director, Crustal Geophysics and Geochemistry Science Center
U.S. Geological Survey
Box 25046, Mail Stop 964
Denver, CO 80225
http://crustal.usgs.gov/

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Suggested citation:

Ball, L.B., and Teeple, A.P., 2013, Characterization of major lithologic units underlying the lower American River using water-borne continuous resistivity profiling, Sacramento, California, June 2008: U.S. Geological Survey Open-File Report 2013–1050, 13 p., http://pubs.usgs.gov/of/2013/1050/.



Contents

Abstract

Introduction

Acknowledgments

Methods

Geophysical Characterization of Major Lithologic Units

Conclusions

References Cited


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