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>

<< Dec 2019 >>
MTWTFSS
25 26 27 28 29 30 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 2 3 4 5

3rd International Congress Hydraulic Engineering Structures and Dredging

Russia’s leading maritime industry Media Group PortNews (www.portnews.ru) holds a traditional annual Congress “Hydraulic Engineering Structures and Dredging” in Moscow. 

The two-day Congress includes the 7th International Forum of Dredging Companies and the 3rd Technical Conference “Modern Solutions for Hydraulic Engineering”.

Infrastructure development is among the real sources of Russia’s economy growth. Construction of port facilities and new hydraulic engineering structures on the country’s inland waterways constitute an essential part of all infrastructure projects. It is important to take into account the best international practices to implement these projects effectively.

The program of the Congress will be devoted to the latest technologies for dredging and hydraulic engineering works. Speakers and delegates will refer to real projects to discuss specifics features of dredging works, as well as dedicated fleet and equipment involved.

To learn more about event, please, contact the organizing committee: snitko@portnews.ru

read more >

Jobs>

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

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