201916 Hydrodynamic interaction close-call

A cruise ship (CS Orange in the diagram) was moored starboard side to, bow out. Another cruise ship (CS Black) turned on arrival and was backing into its berth, going port side to. While CS Black was nearing its final position, the bridge officer on the starboard wing reported that CS Orange had begun to let go lines and was departing, yet the bridge team of CS Orange had not announced their intention to depart the berth on VHF 16 or the port working frequency. Several of CS Black’s lines were now ashore when CS Orange departed its berth and rapidly increased its speed.

The speed of CS Orange was close to 5 knots as its stern passed the bridge wing of CS Black. With a lateral distance of only 30 metres between the vessels, CS Black began to surge ahead. The relatively small under-keel clearance probably magnified the interaction effects. Thankfully, since the bridge team of CS Black were aware of the potential risk of hydrodynamic interaction, no strain had been taken on the spring lines until CS Orange was well clear.

 

Lessons learned

• The surging of CS Black during mooring could have caused the spring line to part had it been secured, which in turn could have caused serious injury or even death.
• During a mooring operation, it is important to maintain broad situational awareness. One cannot always count on the bridge teams of nearby vessels to exercise good and safe seamanship.

Editor’s note: For more hydrodynamic interactions see MARS 201703 and 201704 among others.