What is navigable mud and why is it important?

Navigable mud is a sediment layer found in waterways, primarily composed of fine particles such as silt and clay, organic matter and water. Its formation is the result of natural processes on and near waterways, such as riverine sediment transport, tidal actions and biological activity.

Unlike other sediment types, navigable mud has the distinctive characteristic of being semi-fluid, which allows vessels to navigate through it, under specific conditions. For safe navigation into ports and harbours, it’s important to keep space available under a ship keel – otherwise known as the under-keel clearance. Without this, challenges such as increased risks of grounding and damage to vessels can present themselves, compromising safety and operational efficiency.

The more favourable option to ensure under-keel clearance is dredging – however, navigable mud is a habitat for various marine organisms that thrive in these nutrient-rich environments and many marine ecosystems are particularly vulnerable to the disturbances caused by dredging. And from an operational perspective, the costs associated with dredging are substantial.

Innovative strategies are needed to ensure the management of navigable mud is controllable. The key lies in reducing the volume of mud that needs to be dredged, which can be achieved through more precise surveying and better alignment of mud management practices aligned to environmental and operational goals.

Advanced sonar systems, real-time monitoring tools and predictive modelling can all provide a more accurate understanding of mud dynamics. By improving the precision of surveys, maritime operators can identify areas where mud accumulation poses a significant risk to navigation, while also recognising zones where dredging may be unnecessary. Stema Systems’ innovative RheoTune and Silas2D technology optimises dredging operations through precise measurements of density and yield stress profiles of fluid mud simultaneously, for nautical depth determination in real-time. This data is imported into Silas2D, a sub-bottom profiling system to ensure high-resolution fluid mud data of the harbours area.

Additionally, advancements in environmentally conscious tools such as Tiamat are beneficial – the innovative hydrodynamic dredging machine. By dredging with nature, Tiamat redistributes sediment within the water column, allowing the natural tides to take the sediment away. Two pumps are used to inject water into the sediment overlying the bed of the harbour, whilst the first pump extracts the diluted silt and pumps it up a flume, from where it is released into the water column. The silt can be relocated either within the estuarine system on a flood tide or washed out of the harbour on an ebb tide through the natural tidal currents.

To find out more about Tiamat and the latest news from Haven Dredging, please visit www.havendredging.com