A major problem for Belgian seaports is the fact that the channels and harbours silt up very quickly. The zone between Ostend and the mouth of the Western Scheldt is known as one of ‘maximum turbidity’, meaning that it is a zone where the fine material in the water is at a maximum. 

Due to this silting up of the access channels, the government is obliged to carry out major dredging works to ensure the necessary depth of the channels and ports. Most of the dredged material is redeposited at sea at designated dumping sites. Every year around 10 million tons of material (dry matter) is dredged and redeposited in the sea. Part of this material is, however, displaced from the dumping sites and moves back to the places from where it was originally dredged, meaning that it has to be dredged again. Research is therefore needed to find more efficient dumping sites where the material is more likely to remain in place. 

Knowledge of the origin and movement of fine mud in the water is also important for other reasons. The quantity of material in suspension also determines water transparency and the high concentration of material in suspension is the reason why the Belgian seawater looks so grey. Water transparency is an important factor for organisms that live in the water and on the seabed, and which need light to grow and live. It is also known that polluting substances can attach themselves to these very fine particles.