Interaction risks in narrow channels

Captain John Taylor and Taslim Imad of the Loss Prevention Team at Steamship Mutual have written on the risks of interaction in narrow channels.

The Marine Safety Investigation Unit (MSIU) of Transport Malta has recently published investigation reports for two accidents which took place in narrow channels. Details of the two events indicate that the accidents were caused by interaction.

The first incident, the grounding of MV APL Danube, took place in the Suez Canal, Egypt with a pilot on board. The APL Danube was approaching the km 133 mark in the canal when the vessel suddenly sheered to starboard. In an attempt to correct the heading the helm was ordered hard over to port and speed was increased.

However, the vessel continued to swing to starboard and ran aground.

MSIU stated in their report that “the vessel suffered loss of directional power due to bank effect, since she was in close proximity to the Eastern bank of the Suez Canal”.

The second incident, a collision, took place in the GhentTerneuzen Canal, Belgium, when the inward-bound MV Klara sheered to port across the canal, colliding with the tug Braakman, which had been assisting outward-bound MV Posidana, a vessel constrained by its draught.

The Klara was originally navigating in the middle of the canal, but had altered course slightly to starboard to provide more sea room to the MV Posidana. Just after passing the outbound barge Imperial Gas, that was ahead of MV Posidana, the pilot on the Klara started to very slowly alter course to port, to align the vessel’s heading with the canal channel track of 168°, parallel to the shoreline. The manoeuvre was initially uneventful until, with the MV Posidana bow still about 450m away, the vessel started to turn quickly to port, eventually colliding with the tug Braakman and the MV Posidana then ramming the starboard side of MV Klara.

The Steamship Mutual Risk Alert draws Members’ attention to the risks when vessels are navigating in narrow channels and highlights factors that give rise to this effect (see link below).

The Club said that it could not over-emphasize the importance of properly understanding and appreciating the phenomenon of Interaction when navigating in a narrow channel, and for the bridge team to be fully aware of their vessel’s characteristics.

It said that navigation in narrow channels should be carried out at slow speed with due regard to the local hydrographical conditions. A vessel’s speed should be appropriate for the depth of water, such as to adequately maintain control, with sufficient contingent power available to aid the rudder if necessary.

If a reduction in speed is required, it should be made in good time, in anticipation of the possible effects of interaction. A low speed will lessen the increase in draught due to squat as well as the sinkage and change of trim caused by interaction itself.

Depending upon the dimensions of the vessels and the channel, speed may have to be restricted. When vessels approach each other at these limiting speeds, interaction effects may be magnified, and a further reduction in speed may be necessary.

Those in charge of the handling of small vessels were urged to understand that more action and greater vigilance might be required on their part, particularly when passing large vessels which might be severely limited in the actions that they can take in a narrow channel.

Regardless of the relative size of the vessels involved, an overtaking manoeuvre should only commence after the vessel to be overtaken has agreed to the manoeuvre.