|2006 Philadelphia Annual Meeting (22–25 October 2006)|
|Paper No. 19-10|
|Presentation Time: 10:45 AM-11:00 AM|
APPLICATION OF A SEDIMENT-BUDGET APPROACH TO EVALUATE SOURCES AND SINKS OF HG-CONTAMINATED SEDIMENT IN A GRAVEL-BED RIVER, S. RIVER, VIRGINIA
SKALAK, Katherine J.1, PIZZUTO, James1, NARINESINGH, Pramenath1, RHOADES, Erica2, and O'NEAL, Michael1, (1) Department of Geological Sciences, University of Delaware, Newark, DE 19716-2544, firstname.lastname@example.org, (2) Geography Department, University of Delaware, Newark, DE 19716|
The purpose of this study is to construct an annual sediment budget for Hg-contaminated silt and clay for South River, a steep gravel-bedded stream in western Virginia. The significant sediment-related processes in the study area are suspended sediment transport, bank erosion, levee deposition, and storage of fine-grained sediment trapped by large woody debris (LWD) in the channel margins (“channel margin storage”). Suspended sediment fluxes for the study reach were determined using a dimensionless regional sediment-rating curve. Bank erosion rates were measured using aerial photographs from 1937 and 2005. Floodplain deposition rates were estimated using dendrochronology. The unique contribution to the sediment budget is channel margin storage. Field observations indicate that silt and clay is stored in the near-bank regions of the channel. The volume of storage in these deposits is equivalent to less than 5% of the river's annual suspended sediment load and annual deposition in these deposits is less than 1% of the total annual load. Sediment storage in the near-bank regions is a result of reduced velocity caused by the bank obstructions. Storage occurs in four different geomorphic settings: 1) long pooled sections caused by bedrock or old mill dams, 2) the upstream areas of pools in pool/riffle reaches with abundant LWD, 3) bank obstructions usually caused by trees, 4) side channel backwaters where flow separates around islands. These deposits have been cored and analyzed for Hg, grain size, loss-on-ignition, and they have been dated using post 1950 “bomb radiocarbon”. The sediment budget, when combined with Hg concentration data, suggests that Hg is produced from bank erosion, stored in levees and channel margin deposits, and exported from the system downstream.
2006 Philadelphia Annual Meeting (22–25 October 2006)
General Information for this Meeting
|Session No. 19|
Sources, Transport, Storage, and Delivery of Sediment in the Chesapeake Bay Watershed
Pennsylvania Convention Center: 108 A
8:00 AM-12:00 PM, Sunday, 22 October 2006
Geological Society of America Abstracts with Programs, Vol. 38, No. 7, p. 55
© Copyright 2006 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.