This report summarizes a grounding incident involving a small cargo vessel navigating a tidal river. The information is based on a preliminary safety investigation conducted by the Marine Accident Investigation Branch (MAIB) of the United Kingdom.
What Happened
A cargo vessel, measuring 80 meters in length and 12 meters in beam, entered a tidal river en route to a port with maximum allowable dimensions of 83 meters LOA and 13 meters beam. Two pilots boarded at the sea buoy, with pilot A taking the helm under assessment by a senior pilot (pilot B). A brief Master/pilot exchange took place before river entry. After passing a swing bridge, pilot A initiated speed reduction in preparation for berthing. Observing the vessel slightly off the planned track to port, he applied 30 degrees of starboard helm and engaged the main engine ahead.
The vessel’s bow rapidly swung starboard and, within one minute, grounded bow-first on the river’s western bank at a speed over ground of approximately 6 knots. The stern was then forced onto the eastern bank by the flood tide, resulting in the vessel becoming wedged across the waterway. Initial efforts to refloat the vessel were unsuccessful. Refloating was achieved later with the assistance of a tug during the evening flood tide.
Why It Happened
The incident was attributed to the bank effect, a hydrodynamic interaction occurring in confined waterways. In response to the perceived lateral deviation, the pilot’s strong starboard helm and engine application were likely excessive and led to the vessel’s rapid swing. The pilot had been conning the ship within a restricted and high-attention environment for nearly two hours, which may have contributed to a lapse in judgment due to fatigue or reduced situational awareness.
Actions Taken
The port authority initiated simulator-based training for pilots and conducted a review of vessel suitability criteria for port transits. A risk assessment for vessel groundings was also completed, including evaluation of the potential safety benefits of mandating escort tugs for certain transits.
Lessons Learned
- Bank effect remains a critical hazard in narrow waterways and must be factored into all manoeuvring decisions.
- While speed reduction is generally effective for mitigating bank effect, excessive helm or propulsion inputs may negate that benefit.
- Prolonged periods of high-concentration navigation can lead to fatigue-related lapses; bridge resource management should account for this with more active team engagement.
- Simulator training and transit suitability reviews are effective tools in enhancing pilot decision-making and risk awareness.
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Source: The Nautical Institute
