IADC: Challenges of Optical Backscatter Monitoring

Image source: DHI

In the latest edition of their Terra et Aqua magazine, the International Association of Dredging Companies (IADC) put a special spotlight on the challenges of optical backscatter monitoring in mixed sediment environments.

Optical backscatter instruments (OBS) are very popular instruments for measuring suspended sediments in the field. In this IADC article, an analysis is given based on laboratory tests, numerical analysis and field measurements.

OBS instruments are simple and effective devices for measuring turbidity. The signal needs a transfer function to convert turbidity to total suspended matter concentration (TSMC). The transfer function is dependent on several variables, notably the grain size distribution.

There is an almost linear relationship between turbidity (e.g. given in NTU) and TSMC for specific sediment properties. Suspended sediment properties may shift in time either due to flocculation or through erosion and deposition, which may result in erroneous results as calibrations are usually made for stationary conditions.

The present analysis demonstrates that for stationary sediment properties, there is a linear relationship between turbidity and TSMC, but also that the relation is not linear if the sediment properties shift in time.

The conversion factors are shown to tend to an exponential function of median grain size and thus the calibration function between turbidity and TSMC for a mixed sediment environment also becomes exponential.

This is demonstrated through thorough analysis of excessive field measurements of suspended sediment dynamics in a mixed sediment non-tidal lagoon on the Baltic coast in southern Denmark.

Share this article

Follow Dredging Today

Events>

<< Aug 2019 >>
MTWTFSS
29 30 31 1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31 1

Eastern Chapter WEDA Fall 2019 Conference

Wednesday (10/16/19) afternoon will start the program with an opportunity to take the Dredging 101 course.

read more >

10TH Annual Conference Dredging in India

The conference will focus on strategies and solutions to meet the future dredging requirements…

read more >

Australasian Coasts and Ports 2019

Conference Theme “Future directions from 40°S and beyond” reflects the increasing awareness about the need to find suitable…

read more >

PORTS Conference

The PORTS Conference series is internationally recognized as an outstanding opportunity to network with…

read more >

Jobs>

Looking to fill a job opening?

By advertising your job here, on the homepage of DredgingToday.com, you'll reach countless professionals in the sector. For more information, click below....

apply

Dredging jobs in Abu Dhabi at NMDC

National Marine Dredging Company “NMDC” aims to be the largest dredging player in the Arab’s Gulf region...

apply

Looking to fill a job opening?

By advertising your job here, on the homepage of DredgingToday.com, you'll reach countless professionals in the sector. For more information, click below...

apply