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Close encounters

Ports and harbours - Planning

When planning port developments it is essential that the concerns of mariner users be addressed at the earliest stage, argues Tom Drennan.

There is a kind of unwritten 'food chain' in action when port developments are being considered, with the economists at the top and the construction contractors at the bottom. Somewhere in between sits the input of marine consultants seeking to influence such issues as accessibility for ships, the impact on existing port customers and - of no little significance - will it work?

While the need for accurate environmental data is well understood, it is often the mariner who can add the extra dimension in terms of assessing what will be the true impact on the vessel, and hence downtime and the potential viability of the project.

Examples include the importance of the direction of wind and current. A wind speed which may be regarded as a limiting condition by the engineer may be of less or more concern to the mariner depending on its direction, other factors such as current, shelter from local structures, and the particular manoeuvring characteristics of the vessels.

Here, a marine impact assessment (MIA) can have a role in improving the overall success of the project.

Although an MIA has a number of separate but related elements, each development is different and not all will require the 'full treatment'. The elements required will depend on factors such as the nature and scale of the development, whether it is greenfield or mature, access channel dimensions, and the capacity of the waterways to handle increased traffic. So there is no one set route between the two fixed points of 'start' and 'finish'.

Because of this it is advisable to take the outputs from the environmental model to the next stage, shiphandling simulations, now an established part of port development.

Simulators, such as the one developed by British Maritime Technology, include coefficients for hull hydro-dynamics, propeller design, hull resistance, rudder design, wind loading, machinery performance, and environmental factors. But two hydrodynamic phenomena often underestimated by engineers, are shallow water effect and bank rejection.

At a later stage, full mission simulation has a valuable role to play in allowing pilots and port authorities to practise the vessel manoeuvres and so evolve the optimum berthing procedures, conditions, and use of tugs.

In addition to determining optimum channel dimensions, the output from the shiphandling simulations may also be used for marine traffic modelling.

This is probably where the mariner adds most value, with their real experience of 'driving ships', or of managing traffic flows in a port. Although less common, marine traffic simulation is becoming increasingly important to quantify potential collision risk and port delay.

Eagle Lyon Pope's Animated Marine Traffic Information System (AMATIS) has been used in MIAs in many ports since 1994, modelling different traffic management measures, and assisting developers in decision making by, for example, determining whether the new traffic justifies the building of a new approach channel.

With each of the animated vessels being assigned its own 'domain', AMATIS measures the occasions when the domains of ships under way interact. This is logged as an 'encounter' - not in itself a collision risk but an indication of potential risk and, importantly, a measure of the change in risk resulting from the new traffic.

The next stage is marine risk analysis. Measurement of future potential collision risk, and comparison with historic data for that port and similar ports, allows further consideration to be given to the project at the most effective stage. Here again, a mariner's input is complementary to that of the lead developers.

After the studies comes the time for hard decisions. The project must be measured against certain criteria, and judgements made about how criteria on such things as risk or delay are set.

There will always be an element of subjectivity, but the MIA process allows for iterative changes and measurable outputs which can be benchmarked against other port developments, thereby supporting the planning process.

Early, logical, and measurable assessment of the marine issues can pay dividends and make an important contribution to the overall success of the project.

In an industry which is becoming ever more dominated by the requirement to 'prove it', the mariner input - which is complementary to the other disciplines - should not be left to the end!

Tom Drennan is marine manager at consultant Eagle Lyon Pope

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