In Situ Measurements of Settling Velocity near Baimao Shoal in Changjiang Estuary
Publication: Journal of Hydraulic Engineering
Volume 137, Issue 3
Abstract
At the South Branch of the Changjiang Estuary near Baimao Shoal, two in situ approaches were used to estimate the settling velocity, , of suspended, fine-grained sediments. The first approach was used when the current was less than and was based on measurements from an optical backscatter sensor (OBS-3A) and a laser in situ scattering and transmissometer (LISST-100, Type C). A modification, using the measured ratio of volume concentration for each floc size class to the total volume concentration as a weighting factor. To improve a previously published approach, a better algorthim was implemented to estimate . Results of the modified approach (0.4 to ) are about twice those of the original approach, which assumes that all sizes of flocs have the same floc density. The second approach used the Rouse equation to estimate the depth-averaged when the current was strong and nearly steady around maximum ebb. Results from the second approach show a much greater depth-averaged (4– ). This is attributed to the large bed shear stresses (between 3 and 3.6 Pa) bringing large sediments into the water column.
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Acknowledgments
Sincere appreciation goes to the Special Scientific Research Project of the Ministry of Water Resources for Public Benefits (Grant No. UNSPECIFIED200701026), the General Program of the National Natural Science Funds (Grant No. NNSFC50709007), the National Key Basic Research Development Program (973 project) of China (Grant No. UNSPECIFIED2010CB429002) and the Postgraduate Scientific Innovation Project of General Colleges and Universities in Jiangsu Province (Grant No. UNSPECIFIEDCX07B_135z). Support for the sabbatical leave from the Virginia Institute of Marine Science for the third writer is sincerely acknowledged. Mr. Huang, S.-C. and Mr. Zhou handled the LISST-100. The logistical help from Mr. Hu, G.-D. and Zhang, Z.-L, from the Survey Bureau of the Hydrology and Water Resources of Changjiang River Estuary, the Changjiang Water Resources Commission, is gratefully acknowledged. Review comments and help from Drs. C. Hobbs and D. A. Lyn and the anonymous reviewers are also sincerely acknowledged.
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Published In
Journal of Hydraulic Engineering
Volume 137 • Issue 3 • March 2011
Pages: 372 - 380
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Mar 24, 2009
Accepted: Aug 18, 2010
Published online: Aug 31, 2010
Published in print: Mar 1, 2011
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