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Quantification of sediment concentrations and fluxes A comparison between optical and acoustic measurements Utrecht, 11 June 2013 – Emile Lemey.

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Presentation on theme: "Quantification of sediment concentrations and fluxes A comparison between optical and acoustic measurements Utrecht, 11 June 2013 – Emile Lemey."— Presentation transcript:

1 Quantification of sediment concentrations and fluxes A comparison between optical and acoustic measurements Utrecht, 11 June 2013 – Emile Lemey

2 Management JDN Departments DREDGING Marine Environmental Department MARINE ENVIRONMENTAL DEPARTMENT SEDIMENTS SOIL GROUNDWATER SPECIAL WASTE Envisan WHO?WHO? ENVIRONMENTAL QUALITY HEALTH SAFETY SECURITY ENVIRONMENT QHSSE

3 Management JDN Departments DREDGING Marine Environmental Department MARINE ENVIRONMENTAL DEPARTMENT SEDIMENTS SOIL GROUNDWATER SPECIAL WASTE Envisan WHO?WHO? ENVIRONMENTAL QUALITY HEALTH SAFETY SECURITY ENVIRONMENT QHSSE

4 WHEATSTONE Secondary Stabilisation Project WHAT?WHAT? Dredging near sensitive marine habitats  Intensive dredge plume monitoring  Hind cast hydrodynamic modelling

5 WHEATSTONE Secondary Stabilisation Project WHAT?WHAT? Dredge plume monitoring -Daily transects around CSD -Perpendicular to current direction -Downstream of turbidity source

6 MONITORING METHODS 1)Optical measurements -YSI 6920 V2 multi-parameter probe -Davit with an electrical winch -Undulating motion -Turbidity, depth, temperature, conductivity and salinity -Turbidity  SSC with conversion coefficient 2)Acoustic measurements -Acoustic Doppler Current Profiler (ADCP) Workhorse Mariner (Teledyne RD Instruments) -VISea Plume Detection Toolbox (PDT) software (Aqua Vision) -Mounted in moon pool of vessel, fixed depth -Current speed and direction -Backscatter data  SSC HOW?HOW?

7 MONITORING METHODS 3)Integration positioning system / loggings -Through software (QINSy and Visea PDT) -GPS/DGPS data  absolute flow velocity and direction HOW?HOW?

8 POST PROCESSING 1)Acoustic method -Sediment flux calculation in Visea PDT 2)Optical method -Data outlier removal -Surfer surface modelling software (© Golden Software) -Quantification of total flux (kg/s)  HOW?HOW?

9 -Most transects: similar sediment profiles RESULTS Optical: Acoustic:

10 -Some differences in profiles RESULTS Optical: Acoustic:

11 -Some differences in profiles RESULTS Optical: Acoustic:

12 RESULTS -Quantification of fluxes

13 RESULTS -Quantification of fluxes

14 -Point measurement comparison RESULTS

15 Both methods yield similar profiles Real-time vs. Intensive post processing Flux quantification results differ TSS concentrations by acoustic measurement overestimated?  Maybe due to Algorithm used in processing ADCP + PDT very useful as visualisation tool Not yet alternative for optical TSS quantification of complex dredge plumes CONCLUSIONS

16 OFFICE JAN DE NUL N.V. Tragel 60 – 9308 HOFSTADE-AALST Belgium Tel.: – Fax: Website:


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