case study 4 Flashcards
(28 cards)
Why is sediment transport important in the Scheldt Estuary?
It is a vital shipping route requiring constant dredging.
What was the study focus?
Analyze sediment transport using existing data and new in-situ measurements.
Which initiative is this study part of?
Agenda for the Future (Flemish–Dutch initiative).
Which locations were studied?
Sill of Hansweert and Sill of Frederik.
What data was used in Part 1?
Multi-beam echo sounding.
What was the goal of the echo sounding analysis?
Identify natural sedimentation during periods without dredging.
What did the Hansweert site show?
Strong sedimentation near green buoy, linked to nearby sandbar.
What did the Frederik site show?
Sediment spread more widely across the channel.
What was the conclusion from echo sounding?
Each sill has unique sediment dynamics.
What equipment was used in the measurement campaign?
Two HILAS frames with ADCPs, OBS, YSI sensors, batteries.
Where were the HILAS frames placed?
On either side of a guidance wall at Sill of Frederik.
What was the purpose of the measurement campaign?
Measure flow and suspended sediment during spring–neap cycles.
What challenge occurred with ADCPs?
Blank zones between top and bottom sensors.
How were the blank zones solved?
Theoretical interpolation and Rouse profiles.
What methods were used for calibration?
Pump samples and LISST for grain size.
What does the raw acoustic signal convert to?
dB (decibels), then adjusted and calibrated to mg/L.
How was the data fitted?
Two linear segments with a kink at ~80 dB.
What did the flow show?
Stronger during spring tide, especially near the surface.
When is sediment transport stronger?
During the flood phase.
What does a low Rouse number (~0.04) indicate?
Uniform fine sediment throughout the column.
When is sand transported?
At max flood and ebb.
When is mud transported?
At slack low water.
What is the total output used for?
Depth-averaged sediment concentration + velocity to validate models.
Which sensors are best for sand?
Acoustic (ABS) – peak flood/ebb.
