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| Title: | Geologic conditions underlying the 2005 17th Street Canal levee failure in New Orleans |
| Author (s): | Rogers, David Boutwell, P. G. Schmitz, W. D. Karadeniz, D. Watkins, M. C. Athanasopoulos-Zekkos, G. A. Cobos-Roa, D. |
| Department/Lab Affiliations: | Geological Sciences & Engineering Natural Hazard Mitigation Institute (NHMI) |
| Keywords: | Louisiana failures hurricanes levees marshes swamps |
| Issue Date: | 2008-05 |
| Publisher: | American Society of Civil Engineers |
| Citation: | Rogers, J. D. , G. P. Boutwell, D. W. Schmitz, D. Karadeniz, C. M. Watkins, A. G. Athanasopoulos-Zekkos, and D. Cobos-Roa. Geologic Conditions Underlying the 2005 17th Street Canal Levee Failure in New Orleans. J. Geotech. and Geoenvir. Engrg. Volume 134, Issue 5, (May 2008): 583-601. |
| Abstract: | A careful program of subsurface sampling and cone penetration test soundings was employed to characterize the geologic conditions beneath the failed portion of the 17th Street Canal levee in New Orleans, where a 150 m long section of the levee and floodwall translated up to ~16 m when flood waters rose to 1–2 m of the wall's crest on August 29, 2005, during Hurricane Katrina. The subsurface conditions are characterized by discrete layers of fill placed upon the historic cypress swamp, which is underlain by a deeper, prehistoric cypress swamp. These swamp deposits were consolidated beneath the levee, and in the area of the 2005 failure, the swamp materials infilled a natural depression believed to be an old slough, which dipped below the sheetpile tips for a distance of about 50 m, which corresponds to where the breach appears to have initiated. Detailed examination of the recovered soils suggest that recent hurricanes periodically inundated the swamps with saline and/or brackish water, which cause a mass dieoff of swamp vegetation and flocculation of suspended clays, due to the sudden increase in salinity. These conditions promote deposition of discontinuous clay seams beneath layers of organics, which are then covered by fresh water swamp deposits. This sequence is repeated, like a series of tree rings, throughout the swamp deposits. The cypress swamp deposits lying beneath the levee also exhibit high hydraulic conductivity. These materials contain corky wood, and recovered samples often exhibited densities less than water. Nine of the post-Katrina borings recovered intact samples of a basal rupture surface comprised of organic silty clay exhibited near zero residual shear strength after shearing 80 to 100 mm. |
| Type: | Article - Journal text |
| In Title: | Journal of Geotechnical and Geoenvironmental Engineering |
| Copyright Notice: | This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. Pre-print: archiving status unclear; Post-print: author can archive with restrictions;Restriction: 90 days after publication; Conditions: Publisher's version/PDF cannot be used;Internet site or institutional repository;Must link to publisher version at ASCE Civil Engineering Database(http://cedb.asce.org);Publisher copyright and source must be acknowledged; FULL COPYRIGHT INFORMATION: |
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| title | Geologic conditions underlying the 2005 17th Street Canal levee failure in New Orleans |
| contributor.author | Rogers, David |
| contributor.author | Boutwell, P. G. |
| contributor.author | Schmitz, W. D. |
| contributor.author | Karadeniz, D. |
| contributor.author | Watkins, M. C. |
| contributor.author | Athanasopoulos-Zekkos, G. A. |
| contributor.author | Cobos-Roa, D. |
| contributor.deptlab | Geological Sciences & Engineering |
| contributor.deptlab | Natural Hazard Mitigation Institute (NHMI) |
| contributor.sponsor | National Science Foundation |
| subject | Louisiana |
| subject | failures |
| subject | hurricanes |
| subject | levees |
| subject | marshes |
| subject | swamps |
| date.issued | 2008-05 |
| publisher | American Society of Civil Engineers |
| identifier.citation | Rogers, J. D. , G. P. Boutwell, D. W. Schmitz, D. Karadeniz, C. M. Watkins, A. G. Athanasopoulos-Zekkos, and D. Cobos-Roa. Geologic Conditions Underlying the 2005 17th Street Canal Levee Failure in New Orleans. J. Geotech. and Geoenvir. Engrg. Volume 134, Issue 5, (May 2008): 583-601. |
| identifier.pub.URI | |
| description.abstract | A careful program of subsurface sampling and cone penetration test soundings was employed to characterize the geologic conditions beneath the failed portion of the 17th Street Canal levee in New Orleans, where a 150 m long section of the levee and floodwall translated up to ~16 m when flood waters rose to 1–2 m of the wall's crest on August 29, 2005, during Hurricane Katrina. The subsurface conditions are characterized by discrete layers of fill placed upon the historic cypress swamp, which is underlain by a deeper, prehistoric cypress swamp. These swamp deposits were consolidated beneath the levee, and in the area of the 2005 failure, the swamp materials infilled a natural depression believed to be an old slough, which dipped below the sheetpile tips for a distance of about 50 m, which corresponds to where the breach appears to have initiated. Detailed examination of the recovered soils suggest that recent hurricanes periodically inundated the swamps with saline and/or brackish water, which cause a mass dieoff of swamp vegetation and flocculation of suspended clays, due to the sudden increase in salinity. These conditions promote deposition of discontinuous clay seams beneath layers of organics, which are then covered by fresh water swamp deposits. This sequence is repeated, like a series of tree rings, throughout the swamp deposits. The cypress swamp deposits lying beneath the levee also exhibit high hydraulic conductivity. These materials contain corky wood, and recovered samples often exhibited densities less than water. Nine of the post-Katrina borings recovered intact samples of a basal rupture surface comprised of organic silty clay exhibited near zero residual shear strength after shearing 80 to 100 mm. |
| type | Article - Journal |
| type.DCMIType | text |
| type.status | Postprint |
| relation.isPartOf | Journal of Geotechnical and Geoenvironmental Engineering |
| rights | This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. |
| rights | Pre-print: archiving status unclear; Post-print: author can archive with restrictions;Restriction: 90 days after publication; Conditions: Publisher's version/PDF cannot be used;Internet site or institutional repository;Must link to publisher version at ASCE Civil Engineering Database(http://cedb.asce.org);Publisher copyright and source must be acknowledged; |
| rights.URI | |
| identifier.persist.URI | |
| date.available | 2009-01-05T18:04:23Z |