Abstract
In order to establish the dimensions of approach channels and manoeuvring areas, PIANC guidelines consider two phases: Concept Design and Detailed Design.
The Concept Design Stage includes preliminary design of channel width, depth and alignment using empirical formulae, together with limited data related to ships and environmental conditions. Only rough estimates of the dimensions of the proposed channel (width, depth and alignment) are determined. The results sometimes are conservative, because general guidelines cannot assess all case-specific features and conditions.
The Detailed Design Stage is a more rigorous process intended to validate, develop and refine the Concept Design. The operational aspects are checked, referred to weather conditions, ship size and manoeuvring capacity, tug assistance, piloting, etc. If the conditions are relatively simple and all the design criteria are easily fulfilled, there may be no need to make significant adjustments to the Concept Design. But in most cases additional analyses are necessary to determine a more accurate design that will definitely be safe and usable without unnecessary expense. In this case, much more detailed information is needed regarding fairway geometry, weather and current conditions, ship characteristics, manoeuvring strategies, etc.
Real-time Manoeuvring Simulation is the most advanced tool to be used in this process. A realistic, detailed, complete representation of the port and its particular physical conditions is built. Ship behavior in shallow waters and restricted channels can be accurately reproduced, together with the assistance of specific tugs. Moreover, Pilots and Captains can take part in the analysis, so their expertise and the perception and decision making factors are incorporated to the design.
Real-time simulation, if properly defined and executed, can absolutely help to define a more accurate design and operation conditions of a port area. A detailed approach based on specific local conditions (geometrical and environmental), specific ships (dimensions, propulsion and steering capacity), AtoN and tug assistance will provide complete, accurate and detailed indications on the execution of manoeuvres, both in normal and emergency conditions. Therefore, precise operation limits, manoeuvring strategies and contingency plans can be elaborated also involving human factor.
In some cases, the analysis of new scenarios is outstanding, such as the access of new larger ship classes to existing ports (container vessels, LNG carriers, cruise vessels, …). The limitation in space and therefore the reduction of the manoeuvring areas becomes a critical factor. The final design will depend not only on the dimensions obtained from the statistical analysis of the simulation results but also on many other factors involved. These concern mainly Change Management (adaptation to key factors of the project in their new configuration) as well as the creation of a Confidence Building Process.
For this purpose, a technical committee representing the main experts in the project (Port Authority, Operators, Designers, Maritime Authority, Shipowners, Pilots, Tug Companies, ...) is recommended to be created to participate in common workshops during the design process, in order to check input data and assumptions, survey the simulations, contribute to the discussions and finally validate the simulation results and include their opinions.
This process is considered decisive in relevant projects involving such new scenarios, where important changes are proposed (increase in the size of vessels or significant changes in the geometry of the manoeuvring areas, especially if additional dredging is required).
In this way, the management of the change of all relevant factors by seafarers in charge of the manoeuvre (detailed knowledge of the behaviour of the new vessels, modified operational limits, training process of the new manoeuvring strategy, detailed knowledge of the modified manoeuvring areas and new AtoN, definition of communication procedures between Pilots and Tug operators, definition of operation procedures, ...) is totally connected with the proposed design. This process will finally conclude with the definition of a detailed procedure describing all relevant factors to take into account so as to operate the design vessel in the port.
Consequently, in most cases, the final manoeuvring areas (geometry and dimensions) are directly related to the manoeuvring skills and confidence level that Local Pilots are able to transmit to the main stakeholders of the project.
Interest and Benefit:
During years of port design studies related to navigable areas, the experience is that it is quite often necessary to explain why the manoeuvring areas obtained are sometimes so optimized in dimensions. From the point of view of the nautical advisor and port designer, it is important to highlight that the final design does not only consist of a set of dimensions to be defined, but also a detailed procedure to be fulfilled. This allows to, step by step, reach the final goal, which consists of operating the Design Vessel in the Port under the limiting conditions using the optimum required navigable areas. So, this complete design concept includes not only a geometrical description of the manoeuvring areas but also the consideration of a relevant set of nautical factors and human behaviour.