Ports authorities around the world can now benefit from a new vessel motion forecast tool 

A new CSIR-developed tool can predict the motion of moored ships in a port, for both current wave conditions and forecasted wave events, contributing to operational efficiency and port safety. First tested in the Port of Ngqura in South Africa, the tool can be set up to be port specific and can be integrated into most existing infrastructure.  

Some 13,000 ships enter South Africa’s eight ports annually. These ports process in the order of 10 000 containerised loads per day. The country’s total trade accounts for over 50% of the Gross Domestic Product, where 98% of the country’s trade is carried on ships. Many industries rely on imports and exports via our ports, where a safe port environment, with minimal disruptions while loading or offloading cargo, is critical.  

Delays at ports, caused by weather events and uncontrollable environmental factors such as wind and waves, are common and have far-reaching impacts. Across the world, ports face such problems, which impact their operability and interrupt operations. The motion of vessels that are moored in the ports, can contribute to the operational hindrances and downtime of the port, and also result in the breaking of mooring lines during larger environmental events.  

To assist with the management of mooring and long-period wave problems at ports, the CSIR has developed a vessel motion forecast tool. The tool allows port operators to assess the suitability of different sizes of vessels at berths for current wave conditions as well as forecasted future events. With correct planning, the tool will help to minimise disruptions during quayside operations and contribute to overall vessel safety.  

Mooring problems at ports 

One of the main contributing factors to mooring problems is long-period waves, also known as infra-gravity waves, which are waves that have periods of around 30 to 300 seconds. The behaviour of long-period waves results in different ship motions, where various berths inside a port can experience different wave patterns, which makes it difficult for port operators to predict the resulting ship motions. Solutions to manage the impact of long-period waves on moored vessels motion can be very costly and often involve making structural changes to the ports or adopting specialised mooring systems. 

Excessive downtime can have significant financial impacts on the port. The downtime can, however, be reduced with proper port planning and strategies such as where, when and what size vessels can be moored safely for optimal operational conditions. To help address the problem in a cost-effective way, the CSIR looked into the development of a new forecasting tool which predicts long wave-induced moored vessel motions.  

“Predicting the effects of long wave events on moored ships can be challenging for port operators, but this tool allows them to readily assess and quantify the impact of long-period waves on particular vessels at general berth locations inside the port, removing any guess work. This is achieved by linking numerous state-of-the-art numerical models, enabling the modelling of complete long-period wave climates and the resulting moored ship motions,” says Chris Troch, a senior coastal modeller at the CSIR.  

The CSIR has been providing long wave forecasts to the ports of Ngqura, Cape Town and Saldanha Bay for many years, and although this system has been proven to work well, the impact of these long-period waves at the respective ports has been missing. Recent experience has highlighted the fact that port operators are unable to readily assess and quantify the impact of long waves on a particular vessel based on the forecast alone. Although the port operators might be aware of a long-period wave event on the horizon, they are unable to determine what, if any, effect this will have on port operations. From the prevalence of adverse wave activities experienced at ports, a clear international opportunity for the creation of a stand-alone tool has been developed from mature capabilities. 

Proven in the Port of Ngqura  

The Vessel Motion Forecast Tool was developed and demonstrated at the Port of Ngqura, which utilises the CSIR-developed Integrated Port Operations Support System as input. The Port of Ngqura is situated in Algoa Bay, about 20 km northeast of Gqeberha in South Africa. It is the newest of the South African ports, having commenced operations in 2009. Originally planned as a bulk port, the port has been adapted for container handling. Ngqura’s current primary role is the transhipment of cargoes for the East and West African ports, as well as for inter-continental transshipments.  

In the future, significant growth is planned for the Port of Ngqura. But the port does encounter problems with moored container vessels. 

The berths inside the Port of Ngqura are protected by breakwaters, which provide protection from short-waves, swell and to some extent, long-period waves induced by wave groups. Harbour oscillations can however still be generated by long-period waves penetrating the port, which can have detrimental effects on the behaviour of moored ships in the port.  

In the past, the port has investigated various ways to solve this problem and improve the  mooring conditions at the container quay. Unfortunately most of these solutions are either impractical, have long implementation times or require large capital investments. Many wave-exposed ports around the world experience similar problems.   

Since the Port of Ngqura is one of the most affected ports in South Africa when it comes to long-period waves, it was selected for the development of the Vessel Motion Forecast Tool. Having access to a vast archive of measured wave data for the port – based on previous studies – worked in Troch’s favour as it contributed to accurate model calibrations. 

Beating the variables to minimise wave disturbance at berths  

The interaction between long-period waves, port geometry and moored ships is complex and to accurately predict or forecast long-period waves, numerical models are implemented. The downside to only having a long-period wave forecast however, is that it only gives the wave height at specific locations and it does not provide an indication on moored vessel impact. The wave patterns are generally different for all berth locations, and ship motions are also impacted by factors such as ship size and loaded state of the ship, resulting in only experienced port operators being able to interpret the long-period wave forecast. Due to these reasons, the Vessel Motion Forecast Tool was developed  

The system is innovative in the way it links various numerical models to perform in unison in an automated process to transform available offshore swell wave data to accurate long-period wave-induced moored vessel data. This is enhanced by a unique user-interface display that identifies potential problems per berth and vessel size at a glance, which can be used to manage operations and downtime inside a port.  

The tool is a fully automated, detailed, accurate, cost-effective and easy-to-use moored ship motion forecast system that is able to numerically model processes in detail. The tool has a user-friendly interface and assists in berth planning through its detailed moored ship forecasting. The system is expected to be implementable at various ports without any major restrictions. 

The tool consists of a long-period wave and moored ship motions forecast. Different port clients will be able to access the application via a user interface without having to understand the underlying computational model and CSIR-developed algorithms. The tool predicts moored ship motions for various class ships at certain berth locations and a prediction is given for the current wave condition, including any detected forecast wave event that could be of concern. The predicted vessel motions are linked to international guidelines, to give a container loading operability percentages, it also gives an indication on the safety of the moored ship based on mooring force limiting criteria. This allows port operators to establish whether a ship can be safely moored for the current wave conditions, or for any of the detected wave events in the future. Since each ship size reacts differently for each berth location, the port operators can use the tool to do berth planning in the most efficient way for the expected wave conditions.  

“During system development, info such as port bathymetry, berth layout and ship particulars are required. Measured and forecast wave data are used as input to the system, but this is automated. Measured data is not a requirement, but it does improve the tool performance. No user input is required once the system is set up,” Troch explains. 

The system can be implemented at any port where operations and safety are impacted by severe vessel motions. 

Clearing vessel backlogs  

An end user such as the Harbour Master or Port Captain is responsible for the safe operation of vessels entering, berthing and departing ports. The environment is challenging, and weather and human error are the main contributors to incidents in ports.  

When used correctly, the tool will indicate impending events and the effect of these events at particular berths to the port authorities. The simplistic nature of the tool makes it convenient to use without the need for specialised training.   

The new technology demonstrator was first developed for use by the Transnet National Ports Authority but is relevant to any port impacted by severe vessel motions. Entities that make use of ports, most notably, cargo owners, ship owners, import and export associations, insurance industry and underwriters could all benefit from the tool.