ABSTRACT: Ship drift refers to the unintentional movement of a vessel caused by external forces—such as wind, currents, and waves—acting on the hull without deliberate control by the crew. During navigation, drift may result from failures in the propulsion system or rudder, which impair or prevent maneuverability, leading to course deviations and increasing the risk of grounding or collisions. When the vessel is moored, drift may occur due to extreme environmental conditions or human error that result in the breaking of mooring lines. In such cases, the problem known as unintentional unberthing occurs, often representing an even more critical situation, as the vessel is located near fixed structures such as quays, piers, or other vessels, thereby increasing the probability of accidents and damage to the environment and port infrastructure. This paper presents a study of an estuarine port area, carried out in a Froude-number based reduced-scale physical modeling, to assess the risks associated with the unintentional unberthing of a VLOC-class vessel (400,000 DWT). The study involved the analysis of the drifting trajectory of the vessel under various environmental conditions, positioning of the vessel at the berths, and occupancy of adjacent berths. A digital camera tracking system was employed to monitor the vessel's position at each moment in time, allowing for the assessment of collision risks with port structures or other ships, as well as the potential for grounding in shallow areas. The results of the physical model simulations identified the scenarios with the highest potential for damage, underscoring the importance of strict maintenance of mooring systems and serving as a basis for the development of an emergency action plan to mitigate accident risks in the port area.

KEYWORDS: Safety at Sea, Environment Protection, Meteorological Conditions, Collision Avoidance, Optimal Route, Simulator, Electronic Navigational Chart (ENC), Ports and Harbours

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