The following environmental aspects will affect shipping operations :

Wind

Strong wind will affect shipping in the following ways :

• Cargo operations (especially container handling) cannot be done during times of strong wind. Containers will swing in the wind, making it difficult for container gantry operators to load containers into the container guides on a ship, or to fit them onto the twistlocks that will secure them to hatch covers or onto the container below. The South African ports of Cape Town, Port Elizabeth and Ngqura are particularly prone to being affected by wind.
• The wind can be dangerous for ships entering or leaving port. Pilots may decide that the wind is too strong for the ship to berth or to sail. This applies particularly to high-sided vessels such as loaded containerships, passenger ships, vehicle carriers, large tankers or bulkers when in ballast. These ships present such a high windage that will cause a strong wind to move them uncontrollably.
• A head wind can reduce the speed of a ship – or if the master chooses to keep to the usual speed, the vessel will use more fuel. A stern wind will aid the ship and increase the speed (albeit slightly) and therefore a stern wind can also help to save fuel.
• String wind can drive ships ashore, especially if they are under-powered or disabled.
• Strong winds can cause ships to break their mooring lines which poses serious danger to the ship and to other ships with which she may collide. Two large containerships broke their mooring lines in Ngqura. One smashed into the port’s pilot launch. During a strong south-east gale in Cape Town, an oil rig broke her moorings and was blown into two containerships. Both were serious damaged : one had to be drydocked; the other was withdrawn from service while repaired to side plating were carried out. A fishing vessel was sunk during the incident.
• Strong wind will also cause heavy seas (See paragraph Heavy Seas below)

In 2003, the chartered containership Sealand Express was driven ashore in Table Bay, Cape Town, by strong wind and heavy seas, after dragging her anchor. She was refloated six weeks later. Note the heavy seas that were formed during many hours of strong wind. Photograph : Andrew Ingpen

Heavy Seas

These are the result of strong winds blowing in a constant direction over a long period, and across a long distance. Their affects on shipping are as follows :

• Ships can be damaged by heavy seas. Deck fittings, deckhouses or deck cargo can be damaged by heavy seas sweeping across the deck, while, in heavy seas, ships can suffer structural damage – buckled plating, cracked plating, buckled frames. Ships have been lost because of damage inflicted by heavy seas.
• Because of the danger of suffering damage, ships will reduce speed in times of heavy seas, especially if she is steaming into a head sea.
• Ships in heavy seas will pitch and/or roll. This can become quite violent at times and can make life very uncomfortable for the crew and passengers. The galley staff may find it difficult (even dangerous) to prepare the usual food, while sleep is interrupted by violent rolling. It can also be very difficult moving around a ship in heavy seas, although most seafarers get used to it.
• When the ship is rolling violently, cargo can shift or become damaged.
• Heavy seas can prevent pilots from boarding ships or from disembarking safely. This may result in harbours being closed, and therefore ships are delayed in berthing or sailing.
• Heavy seas can damage harbour installations, especially breakwaters that take the full force of the waves.
• Ships – especially when disabled – can be driven ashore by heavy seas.
• Under some conditions, harbour operations can be affected by range action (i.e. the swell outside the harbour causes a strong current that moves along a wharf. Ships can be moved to such an extent that they snap their mooring lines. Their movement can also halt cargo operations as it becomes difficult to load or discharge.

Off the coast of the Cape Peninsula in summer, the prevailing wind is the south-easter that can be very strong. False Bay is exposed to this wind as is Table Bay. However, an area along the western coast of the Cape Peninsula is sheltered from this wind by the mountains. Ships often anchor in this sheltered area, and even if the wind does blow, it is offshore and poses little threat to causing anchored ships to drag their anchors. (See the map below.)

In winter, the prevailing wind off the Cape Peninsula is from the north-west or west. This generates a significant swell along the western coast of the Cape Peninsula. Under such conditions, ships do not anchor in the area that is sheltered during summer. Although they continue to anchor in Table Bay itself, they sometimes have to leave the anchorage if the wind becomes too strong and/or the swell becomes too great as they are in danger of dragging their anchors and perhaps being driven ashore. (See the map and photograph below.)

Looking forward aboard the tanker Matterhorn Spirit during a voyage across the North Atlantic Ocean. Photograph : Captain Hans Schaefer

Rain

Ships can steam through rain. If visibility becomes impaired by the rain, the officers can use the radar and GPS to navigate the ship safely. However, rain will stop the loading or discharging of weather-sensitive cargoes (i.e. those cargoes that should get wet, such as cement, grain, paper, some machinery, and others.) Container operations can continue during rain.

Fog

Fog is formed when warm, moist air masses meet colder air. The warmer air cools and water vapour in the air condenses, forming fog. Fog affects shipping in the following ways :

• Although they can continue steaming as the officers on watch can use radar and GPS to navigate the ship safely, ships usually slow down during fog. This will delay their arrival at the next port, and, if their ETA at the port has to be met, they will have to make up time by increasing speed. That will cause more fuel to be used.
• Harbour operations will continue, although ships’ movements will be delayed.
• A number of ships have gone ashore or had collisions during fog along the South African coast over the years. Most of these accidents occurred before the invention of radar (during World War 2), although several have also occurred despite the use of radar. For example, the collision between the tanker Texanita and the bulker Oswego Guardian (both with radar) in 1972, and the stranding of the bulker Pantelis A Lemos (also with radar) near Saldanha Bay in 1973 occurred in fog.

Ice

The sinking of Titanic in 1912 still has the world’s attention, especially after the dramatic movie was made. The ship sank after striking an iceberg off the north-east coast of the USA, with terrible loss of life. Into that area, icebergs – originating off the Greenland coast – are brought into the shipping lanes off the north-east cost of USA and Canada but the southward-flowing Labrador Current. Although they pose a danger to shipping, icebergs are tracked by satellite now and ships are given regular reports of the positions of icebergs.

Ice also blocks ports. The entire coast of north-west Europe is ice-free in winter because o f the influence of the North Atlantic Drift that brings relatively warmer water to the region. However, some ports in the Baltic Sea, northern Russia and northern Canada become ice-bound in winter.

The tanker Matterhorn Spirit in the Baltic Sea in winter. Note the ice through which the ship is passing. The ship has a certain level of ice resistance, and can push her way through the relatively thin ice. However, she certainly would not be able to pass through very thick ice. Photograph : Captain Hans Schaefer