Analysis of Wave-Induced Motions and Their Effect on Cargo Securing in Coastal Cargo Vessels on the Nigerian Atlantic Coast

Wave-induced vessel motions including rolling, pitching, and heaving generate dynamic forces on cargo that must be resisted by the cargo securing arrangement to prevent shifting and associated vessel instability or structural damage. This study analyses the wave-induced motion environment and its effect on cargo securing adequacy aboard coastal cargo vessels navigating the Nigerian Atlantic coast between Lagos and Calabar. A quantitative engineering analysis methodology was employed, combining sea state characterisation from metocean records for the Nigerian coastal zone with a rigid body dynamics model of three representative cargo vessel types. Cargo securing calculations were performed in accordance with the IMO Code of Safe Practice for Cargo Stowage and Securing, using the modelled motion accelerations as inputs. Surveys of actual cargo securing practices were conducted aboard twenty coastal cargo vessels during port calls. Results indicate that peak roll and pitch accelerations generated during the West African swell season substantially exceed the acceleration values assumed in simplified cargo securing tables commonly used by vessel officers, suggesting that current cargo securing arrangements may be inadequate during adverse swell conditions. The study finds that horizontal lashing of cargo with synthetic fibre lashings achieves adequate calculated securing for swell conditions, while vertical restraint is the primary deficiency. The study contributes a motion-based cargo securing assessment specific to the Nigerian coastal environment. Keywords: wave-induced motions, cargo securing, coastal vessels, swell conditions, Nigerian Atlantic coast