Damage to Submarine Cables from Dragged Anchors

“Ship anchor damage remains a leading cause of damage globally, presenting a significant and preventable threat to submarine cables”

Submarine telecommunications and power cables form the backbone of global communications and energy networks. Their protection is critical to maintaining international connectivity, economic stability, and energy security. However, these cables face ongoing risk of damage from maritime activities, including commercial fishing, vessel anchoring and increasing development and human uses of the seabed.

This paper highlights the scale of the issue of damage from ships’ anchors and provides guidance on measures to mitigate anchor-related damage to submarine cables.

Impact of Anchor Damage on Submarine Cables

• Damage to submarine cables from dragged anchors account for approximately 30% of incidents each year representing around 60 faults. Damage to these cables is costly, with telecommunication repairs averaging £500k-£1m per incident and power cable repair costs reported to be in the region of £10m-£100m per incident depending on many variables. Downtime from cable damage has the potential to cause disruption to global communications and energy transmission and distribution.
• Dragged anchor incidents can happen following intentional deployment of the anchor or when the anchor deploys unintentionally while underway due to mechanical failure.
• Dragged anchors can damage multiple cables during a single event, heightening the risk of potential disruption due to multiple faults occurring at the same time.
• As well as disruption to communications or electricity networks, it can cause a backlog for repair vessels if multiple cables require repairing at the same time, therefore the impact of a dragged anchor can be more significant than a single event.
• It is worth noting that generally only those incidents which cause disruption to communications or electricity supply get media attention, however far more incidents of cable damage occur each week than is covered in the news. Therefore coverage can lead to the speculation that such incidents are uncommon or suspicious – however such incidents can be attributed to poor seamanship practices, equipment failure or improper stowage of anchors.
• It is important to highlight that there are cable ships located in strategic global locations dedicated to repairing submarine telecommunications cables.

Anchors: A Leading Cause of Cable Damage

• An ICPC White Paper published in 2011 demonstrated through use of AIS monitoring that anchors were a far more significant cause of damage than had previously been thought, where more incidents of damage had been attributed to fishing each year. This represented a marked increase in anchor-related incidents compared to earlier data¹.
• One of the most significant anchor drag events in recent history occurred off Sicily in 2008, where a ship dragged its anchor for 300 km, damaging six submarine cables. Such incidents can disrupt multiple cables in proximity, magnifying the impact of an event^{2 [?]}.
• Another example is the incident between the Channel Islands and Cornwall, UK where a vessel deployed anchor in poor weather, causing damage to several telecommunications cables³ .
• There was another incident on 17 March 2016 where a vessel dragged its anchor causing damage to telecommunications cables and a power cable, which cut off the electricity supply to the Isles of Scilly⁴ for a significant period of time.
• The Chilean flag container ship Aconcagua cut three of the then 4 cables linking the United States to Europe in 2002 while sailing from Philadelphia to New York City. The captain erroneously attributed the reduction in the ship’s speed during a gale to the wind when in fact it was the ship’s anchor dragging. Investigation revealed that the anchor windlass had only been secured with the brake and the chain stopper had not been used.
• The Liberian flagged vessel Blue Princess damaged three submarine cables in the Red Sea in 2012. Over a period of 12 hours on 17th February 2012, SEA-ME-WE 3, EASSy, and EIG, causing multiple cable faults. The vessel could be tracked using AIS as crossing the cables at a similar time as faults were reported and appeared to become fastened to the cable with the speed reducing to zero at the time of the final fault during that period.
• Several cruise ships anchored in Lyme Bay lost their anchors during the COVID-19 pandemic. The MAIB report⁵ highlighted that The International Association of Classification Societies (IACS) advises that the anchoring equipment is not designed to hold a ship of fully exposed coasts in rough weather or to stop a ship that is moving or drifting.
• An Incident in the Great Lakes, Michigan of an anchor being dragged without detection is reported⁶ as having damaged pipelines and 5 cables with the anchor having been deployed for 36 hrs covering approx. 600km causing significant damage.

Accidental Anchor Deployment

Accidental deployment of an anchor, without the crew’s knowledge, remains rare but can be possible due to the following factors:

• Anchors must be fully secured before departure using multiple securing mechanisms, including the windlass brake, bar stopper, and pelican hook/devil’s claws, tightened with bottle screws. Failure to do so can lead to unintended anchor deployment.
• Poor upkeep of anchor securing equipment increases the likelihood of accidental release.
• On large vessels, particularly those with the bridge located far aft, an anchor dropping into deep water may not be immediately detected, as it might not impact vessel steering or performance. This risk is lower on smaller vessels, where an accidental deployment is more likely to be observed.

Intentional Anchor Deployment in Adverse Weather

Intentional deployment of an anchor in rough weather can be hazardous and can lead to submarine cable damage. Key considerations include:

• Anchors are typically deployed when a vessel is stationary or nearly stationary, regardless of weather conditions.
• Deploying an anchor while a vessel is moving at full speed is extremely dangerous and is considered poor seamanship.
• If a vessel experiences an emergency such as machinery or steering failure for example near the coast, anchors may be deployed as a last resort to prevent grounding. However, past incidents have shown that cables can be broken under such circumstances.
• An anchor is not designed to hold fast on the seabed. The weight of the chain in conjunction with the anchor is there to hold the vessel, but in rough weather the vessel will move with the anchor. The ships’ watch must stay vigilant even when anchored.

Recommendations for Mitigating Anchor Damage

1. Improved Vessel Practices:

All vessels should comply with proper anchor-securing protocols using approved mechanical devices. These practices must be mandatory and subject to regular inspections, by vessel owners, class and ports.

2. Insurance

The ICPC has pro-actively highlighted the increasing trend of damage to submarine cables by ships’ anchors to vessels’ Protection & Indemnity Clubs (P&I Clubs) through the production and distribution of a loss prevention, safety and awareness document which also advises on what can be done to prevent anchors from being deployed whilst underway^{7 [?]}.

3. International Maritime Organisation – call to action

The International Maritime Organisation (IMO) should consider:

1. whether the securing of anchors prior to passage should be of a minimum standard methodology and a mandatory requirement.
2. the introduction of interlock on anchors when secured for sea passage with an alarm on bridge.
3. securing of the anchor for sea with the interlock or a reason why the interlock is not used should be a required entry in the vessel logbook and subject to Port State inspection.
4. greater promulgation of the problem via ‘M’ notices (Marine Coastguard Agency) and appropriate notices worldwide.
5. wider port inspections by the state following future submarine cable failures due to anchors.

4. Legal and Regulatory Framework:

International law requires nations to implement the provisions of the United Nations Law of the Sea Convention (1982) by establishing domestic criminal and civil law penalties upon those who damage submarine cables wilfully or by culpable negligence. These measures all contribute to reducing avoidable cable faults and can apply to anchor-related damage to submarine cables resulting from poor practices.

Conclusion

Anchors dragged by vessels, especially those underway, present a significant and preventable threat to submarine cables. By enforcing stricter operational standards, leveraging technology, and enhancing crew training, the maritime community can significantly reduce the risk of damage to this critical global infrastructure. The ICPC continues to advocate for collaborative measures to protect submarine cables and ensure their resilience in the face of increasing maritime pressures.

Resources:

1. The Threat of Damage to Submarine Cables by the Anchors of Ships Underway
2. Global Trends in Submarine Cable System Faults 2019 Update – SubOptic 2019
3. Summary of global repair commencement time analysis (available on request)
4. Reference to incident off Sicily where anchor drag damaged multiple cables. [?]
5. ICPC’s Government Best Practices for Protecting and Promoting Resilience of Submarine Telecommunications Cables.

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© International Cable Protection Committee 1999 - 2025