Canyon Dam Spillway Gorge, Comal County, Texas

AGS GB 30. Canyon Dam Spillway Gorge, Comal County, Texas: Geologic and Hydrologic Issues, by W. C. Ward, Ann Molineux, Shane Valentine, and C. M. Woodruff, Jr. 61 p., 2008.

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About This Publication (excerpted from the Preface)
Guidebook dedicated to the memory of James Lee Wilson. With contributions by Patrick L. Abbott, Edward W. Collins, Rebecca Comeaux, David A. Ferrill, Ann Molineux, Alan P. Morris, James W. Sansom, Jr., Raymond M. Slade, Jr., Kevin J. Smart, William C. Ward, and C. M. Woodruff, Jr.

The...exhumed gorge below the Canyon Dam spillway provides a rare opportunity for geologists to view an extensive section of Glen Rose Limestone, including a significant locus of faulting. This unusual site was created by a combination of human activities (the siting of the spillway above a low-order, high-gradient tributary to the Guadalupe River), coupled with a high-magnitude rainfall event within the upstream catchment of Canyon Lake. In July 2002, this reservoir overtopped its spillway for the first time since the dam was completed in 1964. As noted by Slade (this volume), estimated discharge into the watershed below the spillway was approximately 70,000 cfs...The resulting erosion removed rock, soil, and vegetation, to disclose an erosion-scarred landscape consisting chiefly of bare rock. This has allowed detailed examinations of stratigraphic relations, including complex sedimentary structures, lateral facies relations, fossil assemblages, and a zone of faulting that extends along an extensive reach of the gorge.

It is the purpose of this guidebook to report on investigations addressing various geologic features disclosed within the gorge, as well as the hydrologic processes that resulted in the flooding, overtopping, and erosion. Topics include stratigraphy and paleontology, structural geology, climate and surface-water hydrology, and engineering aspects of dam construction... The implications of what is seen in the Canyon Dam spillway gorge go far beyond this location.

This guidebook is dedicated to the memory of James Lee Wilson (1920-2008), world-renowned expert on carbonate rocks, and author of Carbonate Facies in Geologic History (1975). He was the Harry Carothers Weiss Chair in Geology at Rice University and was Distinguished Professor of Geology at The University of Michigan. After retirement from the academic world, he lived in New Braunfels, Texas and maintained an active professional life as a consulting geologist in the United States and Mexico.


Keywords: Austin Geological Society, Canyon Dam Spillway Gorge, Comal County, guidebooks, hydrology, Texas


Citation
Ward, W. C., Molineux, Ann, Valentine, Shane, and Woodruff, C. M., Jr., 2008, Canyon Dam Spillway Gorge, Comal County, Texas: Geologic and Hydrologic Issues: Austin Geological Society Guidebook 30, 61 p.