17 In Situ Settling Velocities and Concentrations of Suspended Sediment in Spill Plumes
189
3 X 10- 5 m S-I, which is relatively slow. This is because chalk deposits from the Danian
(Tertiary), which consist of small bryozoan fragments, dominate the bed material at
the dredging sites. This material does not flocculate. Settling velocities will diminish
downstream of the source, because the particles with the largest settling velocities will
settle first. The individual fine particles can be transported over long distances before
they settle.
Concentrations of the suspended material close to the dredgers are generally very
high, but these are rapidly diluted downstream of the source. Measurable concentrations can be traced for more than 10 km. The concentration of suspended matter does
not influence the measured settling velocities as no flocculation takes place.
Investigations of possible accumulation areas show that sediment spill from dredging can be traced to specific sites where fine-grained material is normally deposited.
Such areas occur at water depths below 10-15 m. Bed sediment containing spill material
generally consisted of a light -coloured fluffy layer, about 10% of which originated from
dredging operations.
Acknowledgements. The data used in this chapter originate from the Feedback Centre;
0resundskonsortiet has kindly given permission to use it. The author would like to
thank Jens R. Valeur, Anders Jensen and Poul Hammer for discussions and assistance.
References
Knudsen C, Lomholt S (1997) The 0resund Link: Recognition of fine-grained sediments from excavation activities - pilot study -. Danmarks og Gni'mlands Geologiske Unders0gelse, Rapport 1997/114
Kuijpers A, Larsen B, Nielsen PE (1991) Surface sediments in the Danish part of the Sound. DGU Map
Series no. 26, Copenhagen
Bernitt L, Simonsen J (1997) Hindcast no. 9. Feedback Monitoring DHI/7783/90 0269, 0resundskonsortiet,
Technical report
Madsen PP, Larsen B (1986) Accumulation of mud sediments and trace metals in the Kattegat and the
Belt Sea. Report of Marine Pollution Laboratory no. 10. Charlottenlund, Denmark
Pejrup M, Larsen B (1994) Natural sediment transport through 0resund.DHI/7170, 0resundskonsortiet,
Technical report
The Feedback Monitoring Programme for the Fixed Link Across 0resund (1997) DHII7783-8,
0resundskonsortiet, Technical report
Valeur JR, Pejrup M, Jensen A (1996) Particle dynamics in the Sound between Denmark and Sweden.
ASCE Conference Proceedings, Coastal Dynamics '95: International Conference on Coastal Research
in Terms of Large-Scale Experiments, pp 951-962
189
3 X 10- 5 m S-I, which is relatively slow. This is because chalk deposits from the Danian
(Tertiary), which consist of small bryozoan fragments, dominate the bed material at
the dredging sites. This material does not flocculate. Settling velocities will diminish
downstream of the source, because the particles with the largest settling velocities will
settle first. The individual fine particles can be transported over long distances before
they settle.
Concentrations of the suspended material close to the dredgers are generally very
high, but these are rapidly diluted downstream of the source. Measurable concentrations can be traced for more than 10 km. The concentration of suspended matter does
not influence the measured settling velocities as no flocculation takes place.
Investigations of possible accumulation areas show that sediment spill from dredging can be traced to specific sites where fine-grained material is normally deposited.
Such areas occur at water depths below 10-15 m. Bed sediment containing spill material
generally consisted of a light -coloured fluffy layer, about 10% of which originated from
dredging operations.
Acknowledgements. The data used in this chapter originate from the Feedback Centre;
0resundskonsortiet has kindly given permission to use it. The author would like to
thank Jens R. Valeur, Anders Jensen and Poul Hammer for discussions and assistance.
References
Knudsen C, Lomholt S (1997) The 0resund Link: Recognition of fine-grained sediments from excavation activities - pilot study -. Danmarks og Gni'mlands Geologiske Unders0gelse, Rapport 1997/114
Kuijpers A, Larsen B, Nielsen PE (1991) Surface sediments in the Danish part of the Sound. DGU Map
Series no. 26, Copenhagen
Bernitt L, Simonsen J (1997) Hindcast no. 9. Feedback Monitoring DHI/7783/90 0269, 0resundskonsortiet,
Technical report
Madsen PP, Larsen B (1986) Accumulation of mud sediments and trace metals in the Kattegat and the
Belt Sea. Report of Marine Pollution Laboratory no. 10. Charlottenlund, Denmark
Pejrup M, Larsen B (1994) Natural sediment transport through 0resund.DHI/7170, 0resundskonsortiet,
Technical report
The Feedback Monitoring Programme for the Fixed Link Across 0resund (1997) DHII7783-8,
0resundskonsortiet, Technical report
Valeur JR, Pejrup M, Jensen A (1996) Particle dynamics in the Sound between Denmark and Sweden.
ASCE Conference Proceedings, Coastal Dynamics '95: International Conference on Coastal Research
in Terms of Large-Scale Experiments, pp 951-962