SEDL / STP / STP1442-EB / STP11556S

Characterization of a Catastrophic Flood Sediment Layer: Geological, Geotechnical, Biological, and Geochemical Signatures

Tremblay, H
Postdoctorate Fellow, Laval University, Quebec, Quebec

Desrosiers, G
Professor, Institut des Sciences de la Mer de Rimouski (ISMER), Rimouski, Quebec

Locat, J
Professor, Laval University, Quebec, Quebec

Mucci, A
Professor, McGill University, Montreal, Quebec

Pelletier, É
Professor, Institut des Sciences de la Mer de Rimouski (ISMER), Rimouski, Quebec

Pages: 15    Published: Jan 2003

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Abstract

In 1996, an important rainstorm took place in the Saguenay region, Canada, that caused severe flooding and erosion of a large amount of post-glacial sedimentary material. Consequently, about 20 million tons of sediment were deposited in the upstream part of the Saguenay Fjord, covering the recent, contaminated sediments with a 10 to 60 cm thick layer of relatively clean material. This flood layer was distinguished from the pre-flood sediments by various properties: low consistency and low resistance, high water content, the absence of benthic organisms, or the presence of inherited geochemical components. In this study, we evaluated the criteria used by the various investigators to identify the 1996 flood deposit, then finally compared its signature. Subsequently, we assessed the spatial variability of the deposit and its effect on the interpretation of temporal studies.