A method for the evalutation of the frequencies of incidental events related to the ships traffic inside a port using a statistical approach

Aim of this paper is to present a semi-probabilistic, semi-deterministic methodology to evaluate the risk of dangerous spills, and related public and environmental hazard, associated to the navigation in a narrow channel-port. The model is based on a Monte Carlo method with variance reduction technique and can simulate different kinds of ship (tonnage, carried substance) and different kinds of routes to reach or to leave the jetties and the port. The basic event probability (operating error) can evolve in collision with: other flowing or moored ships, sand banks, free jetties, dangerous structures. The possible consequences can be spills of hazardous materials, In addition, the probabilistic model evaluates the frequencies of the events at jetty, as onboard fire and/or explosion, load or unload and berth or unberth accidents. The simulation of the system in study can be performed automatically by a package of two programs: the first (input module) accepts the topological and traffic information about the port; the second (simulation module) simulates the port and the traffic using the inputs created by the first. The simulation program can handle sensitivity analysis. Finally, the methodology has been applied to an idealised but realistic situation of channel-port