The functioning of modern society is highly dependent upon submarine cables and pipelines. These underwater assets crisscross the seabed carrying data, energy, and natural resources, providing connectivity and energy security.
As nations across the world seek to enhance connectivity and generate electricity offshore, the density of cables and pipelines is growing dramatically.
According to industry estimates, approximately 1.4million kilometres of submarine telecommunications cables accounting for approximately 95% of international data transmission ( TeleGeography, 2024), while substantial pipeline networks carry vital hydrocarbons across vast distances.
Shipping hazards associated with underwater cables and pipelines
The intensification of these intricate seabed networks brings with it significant maritime safety concerns, as vessels are increasingly likely to encounter both the asset itself, as well as their associated installation, maintenance or decommissioning activities.
Additionally, any accidental damage to these cables or pipelines is a major concern, not just for the maritime sector, but also because it can have negative economic, social and, depending on the nature of the asset involved, environmental consequences.
Collision
Depending on existing activities and available searoom in an area, during the installation/construction, there is an increase in collision risk through the potential creation of choke points and increased vessel movements.
Collision may result from passing vessels colliding with a third party vessel as cable and pipe layers are slow moving and have restricted manoeuvrability. This is less likely to occur with guard vessels in place, which can communicate with approaching vessels to ensure they maintain a safe passing distance and are aware of the activities.
Collisions may also arise between commercial vessels if they alter their route due to works and end up transiting in closer proximity to other passing vessels.
The impacts during decommissioning activities are generally like those during construction.
Electro-magnetic field
When transmission infrastructure is used, there is a potential impact on ships compasses from the electro-magnetic field generated.
Grounding
Grounding occurs when a vessel inadvertently makes contact with the seabed. Under keel clearance is the vertical distance between the bottom of the ship and the seabed.
Placing and burying cables or pipelines seabed leads to a reduction in under keel clearance. This is particularly relevant where depths are decreasing towards shore as the reduction in clearance is not as critical within deeper waters.
When this involves cables or pipelines damage can occur to the subsea asset, as well as injuries to personnel, damage to a vessel’s hull, risking structural integrity and compromising safety.
Snagging
Subsea cables introduce a risk of snagging, either by fishing gear or vessel anchors.
During the operational phase, fishing with mobile gear such as bottom trawls, beam trawls and dredges can snag cables resting on the seabed causing damage, especially if the cable is suspended above the bottom due to uneven seabed or inadequately protected/buried.
Ship anchors can also cause damage either by being directly deployed onto an asset or by an anchor being dragged across a cable as a ship tries to secure itself. It is also possible for ships to unknowingly drag their anchors long distances, impacting several cables in a row.
Commercial ships may choose to deploy an anchor in an emergency (e.g. loss of power), and whilst unlikely, this could result in cable snagging if the anchor penetrates deep enough. This is more likely to occur in the shallower, coastal waters where there is a higher risk of grounding and a greater need for immediate action. In addition, on rare occasions, accidental deployment of an anchor has occurred due to poor stowage or equipment failure which has damaged subsea cables.
Fishing and anchoring activities have been found to cause around two thirds of cable faults due to snagging.
Mitigation and management of risks
NASH Maritime undertakes Navigation Risk Assessments in line with the International Maritime Organisation’s (IMO) Formal Safety Assessment (FSA) methodology.
This structured methodology aims to enhance maritime safety, including protection of life, health, the marine environment and property, by using risk analysis and cost benefit assessment.
The Navigation Risk Assessment identifies and assesses the potential impacts and effects (cumulative and in-combination) a proposed development and associated activities can have on shipping and navigation by identifying hazards that may be encountered during construction, operation and decommissioning phases of the project.
Based on a review of hazard types, vessel categories and areas, it identifies risk controls to reduce the risk to As Low As Reasonably Practicable (ALARP); and provides recommendations in relation to the safety of the development and co-existence with regards to shipping and navigation.
Conclusion
While the advancement of submarine infrastructure has transformed global connectivity, it simultaneously creates unique challenges for the shipping sector. An accidental strike against an underwater cable or pipeline not only disrupts services and damages the vessel concerned but can also trigger environmental catastrophes, particularly in the case of hydrocarbon spills.
Moreover, the multiplicity of assets now on the seabed increases the risk of maritime accidents not only due to physical encounters but also due to navigational challenges posed by installation, maintenance and decommissioning activities.
To ensure safety of navigation, a coordinated approach involving regulatory oversight, information to mariners, and ongoing dialogue between stakeholders is vital for mitigating risks and ensuring the safety of navigational routes.
If you'd like to discuss this or any other topic relating to shipping and navigation safety, our experienced risk specialists would be happy to help.
References
TeleGeography (2024). “Submarine Cable Faqs.” Submarine Cable FAQs, www2.telegeography.com/submarine-cable-faqs-frequently-asked-questions. Accessed 22 Oct. 2024.
