sediment and flocculation dynamics in the area of zeebrugge marc sas, alexander breugem and andrew...

Sediment and Flocculation dynamics in the area of Zeebrugge

Marc Sas, Alexander Breugem and Andrew Manning

Apr 19, 2023 / Sediment and Flocculation dynamics in the area of Zeebrugge / slide 2

Overview

• Objectives

• Overview of the measurement campaign• Global overview

• Long term measurements

• Through tide measurements • Coastal zone

• Harbour of Zeebrugge

• Near bed measurements using HCBS frame

• INSSEV settling velocity measurements

• Flocculation Dynamics

• Conclusion


Objectives

• The project :

Langdurige monitoring van zout/zoet-verdeling in de haven van Zeebrugge en monitoring van zoutconcentratie, slibconcentratie en hooggeconcentreerde slibsuspensies in de Belgische kustzone

• Waterbouwkundig Laboratorium

• Maritieme Toegang


Objectives

• Objective of the complete project• The first goal of the study and the survey is to detect the

occurrence of near-bed high-concentration mud suspensions (referred to as high-concentration benthic suspensions - HCBS), their dynamic behaviour and the conditions and locations of their occurrence

• The second goal is to gain insight in density currents between harbour and sea, and their relationship to siltation in the harbour of Zeebrugge.

• Objective of the present presentation• Give overview of the measurements and some details about the

flocculation dynamics inside the harbour of Zeebrugge.


Global Overview

• Survey 1 : autumn-winter 2006-2007

• Survey 2 :summer 2007


Long term measurement locations

• Period:

• June 2006-Aug 2007

• RCM9 at:• MOW 1

• Sterneneiland

• CTD at:• LNG terminal

• Hermespier


Long term measurement setup

RCM-9•Velocity•Salinity•SSC•Pressure•Temperature

CTD•Salinity•Pressure•Temperature


Through tide measurement locations

• Harbour entrance:• One spring and one neap tide meas.

• ADCP and SiltProfiler

• Inside the harbour:• One summer and one winter meas.

• SiltProfiler and CTD

• Coastal zone:• Two transects in winter

• Three transects in summer

• SiltProfiler (summer and winter)

• ADCP (summer only)


Through tide measurement instruments : ADCP + CTD

ADCP:•Velocity profile•Sediment concentration profile

CTD:•Salinity (multiple depths)•Temperature


Through tide measurement instruments : ADCP + CTD

Harbour entrance; Neap tide 2h before HW

Harbour; Neap tide 3.30 h before HW


Through tide measurement instruments : SiltProfiler

SiltProfiler:•Sediment concentration profile•Salinity profile•Temperature profile

Specifications

High Frequency (100 Hz)

Wireless Data Transfer via Bluetooth technology

Freefall Profiling

3 Silt sensors:o1 Seapoint BS sensor (0-700 mg/l)o2 Transmittance Extinction Sensors (500-5000 mg/land 3500 – 50000 mg/l)

CTD sensor


Through tide measurement instruments : SiltProfiler

Navigation channel; winter. Avg. tide; 5h after HW

Harbour; summer. Avg. tide; 0.20h after HW


Near bed measurement locations

• Campaigns:• 1 x Summer

• 1 x Winter

• Two different frames

• Deployment: 2-4 weeks


Near bed measurements (HCBS Frame)

• Valeport Midas and RCM-9:• Velocity (0.3 m and 1.0 m above bed)

• Sediment concentration

• Argus: Sediment concentration profile

• Altus echo sounder: Bed level


Near bed measurements (HCBS Frame) : ARGUS

MOW 1 during winter.


Near bed measurements (HCBS Frame) : Altus

MOW 1; Winter


INSSEV Settling velocity measurements

INSSEV floc camera surface electronics in laboratory on RV Lancaster survey vessel

Example of floc images

Hydrodynamic sensors on bed frame being deployed from RV Lancaster survey vessel

1.2 mm


• 15 INSSEV samples from Albert-II Dok

• Obtained 0.6m above the bed

• 8th November 2006

• HW +1hr• 16m deep

• Water Temp ~ 12.8oC

• Salinity = 32

• U = 0.14 m/s

• SPM = 200-400 mg/l

• TMZ (17:00hr – HW+2.5hr)• SPM rose to 5 g/l

• U = 0.03 m/s



• Shear stress range:

• HW+1 = 2 Pa

• TMZ = 0.4 Pa

• LW = 0.15 Pa

• Dmean response:

• 130 m 375 m

• Wsmean response:

• 2 mm/s at HW+1

• Four-fold rise in TMZ to 8.5 mm/s



Sediment & Flocculation Dynamics

• A significant data set has been collected

• There is no evidence for a tick HCBS layer in the navigation channels in the vicinity of Zeebrugge

• Siltation of the harbour of Zeebrugge is strongly influenced by tidal filling and the eddy pattern in the harbour mouth.

• Siltation of the harbour of Zeebrugge shows a strong influence on the neap-spring tidal cycle.

• Density differences due to the fresh water discharge into the harbour have only a limited effect on the harbour siltation.


Conclusion

• A significant data set has been collected on fine cohesive sediment characteristics in the vicinity of Zeebrugge, calling for:• A regular follow up: a series of fixed stations is highly

recommended

• Efforts should be put in characterizing the physical conditions leading to the siltation rate in the access channels and the port

• Integration of wave/wind characteristics is necessary

• Integration of biological parameters is recommended

sediment and flocculation dynamics in the area of zeebrugge marc sas, alexander breugem and andrew...

Documents

area of zeebrugge slide

outer harbour of zeebrugge

harbour lead

area of zeebruggemarc

tide measurement instruments

long term measurement

winteradcp summer

summersiltprofiler summer