How mud and silt plumes behave

years 

“During dredging activities, in order to create land in the sea or to deepen a harbour channel, sediment plumes appear under and behind the dredging vessel. It looks like smoke coming out of a reversed chimney. The plumes consist of mud and silt and give the water a brownish colour. One could compare this to throwing sand in the sea, except that the sand sinks to the bottom quickly. Mud and silt sink slower and may float in the sea for hours; therefore, less light can penetrate the water and this may affect fish, birds that eat fish, and coral. Mud and silt settling out of the plumes could also cover plants and animals on the seabed.

I’m investigating how the plumes behave near dredging vessels in order to know its effects and consequences. It’s difficult to understand how the plumes behave near the ship, because the plumes interact with the vessel and are influenced by its movements. I’m also looking into how the plumes swirl to the seabed. Water mixes with the mud and silt, but how will this change the plumes?

In order to understand the behaviour of the plumes, I’ve measured the water and its contents around a dredging vessel in Australia. A harbour channel had to be deep-ened, which gave me an opportunity to take measurements. We sailed around a dredging vessel in a special type of boat. We put special equipment in the water and navigated it through the plumes.

I collected lots of data thanks to that measurement. I’m currently using this data to see how it corresponds with the simulation of the plumes that I’ve made. I would like to create a model that can predict what percentage of the plumes will swirl around and what percentage will reach the seabed. Additionally, it would be interesting to know what effects the depths of the sea and the ship’s propeller have. Hopefully, this will be a model in which one could enter varying conditions and the model will simulate the plumes and the consequences beforehand.”