Properties of suspended sediment in the estuarine

Authors: Reginald James Uncles John Anthony Stephens Carolyn Harris

Publish Date: 2006/03/28

Volume: 56, Issue: 3-4, Pages: 235-247

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Abstract

Measurements are presented of the properties of suspended particulate matter SPM in the estuarine turbidity maximum ETM of the upper Humber and Ouse estuaries during transient relatively low freshwater inflow conditions of September 1995 Very high concentrations of nearbed SPM more than 100 g l−1 were observed in the lowsalinity less than 1 upper reaches SPM within the ETM consisted largely of fine sediment silt and clay that existed as microfloc and macrofloc aggregates and individual particles Primary sediment particles were very fine grained and typically about 20–30 was claysized at high water The clay mineralogy was dominated by chlorite and illite There was a pronounced increase in particle size in the tidal river upestuary of the ETM The mean specific surface area SSA of nearbed SPM within the ETM was 22 m2 g−1 on a spring tide and 24 m2 g−1 on a neap tide A tidal cycle of measurements within a nearbed high concentration SPM layer during a very small neap tide gave a mean SSA of 26 m2 g−1 The percentage of silt and clay in surficial bed sediments along the main channel of the estuary varied strongly The relatively low silt and clay percentage of surficial bed sediments about 10–35 within the ETM’s region of highest nearbed SPM concentrations and their low SSA values were in marked contrast to the overlying SPM The loss on ignition LOI of nearbed SPM in the turbid reaches of the estuary was about 10 compared with about 12 for surface SPM and more than 40 in the very low turbidity waters upestuary of the ETM Settling velocities of Humber–Ouse SPM sampled in situ and measured using a settling column maximized at 15 mm s−1 and exhibited hindered settling at higher SPM concentrationsWe are grateful to Mr Bob Clifton PML Scientist retired for his assistance with surface area analysis and Mr Norman Bowley PML Technician and Coxswain retired for invaluable assistance and support during the fieldwork The analyses of these data were undertaken with the aid of a grant from the EstProc research programme http//wwwestprocnet EstProc is funded within the joint DEFRA/EA UK Flood and Coastal Defence RD Programme of Fluvial Estuarine and Coastal Processes

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