Exploring the Diverse Environmental Risks of Ship Collisions with Cargo Vessels
1. Introduction
One of the most dramatic forms of pollution at sea is that caused by major oil spills from tankers. Other forms of pollution associated with ships include garbage disposal or sewage through the throwing of non-plastic biodegradable wastes and eutrophication through the release of nutrient salts. However, the usual culprit is the operational discharge of oil from ships. In spite of the fact that the quantity of oil spilt at sea from ship operations is only a third of that from tanker accidents, it has been found that the chronic low-level discharge from shipping has a greater adverse environmental impact. This is because oil operational it is difficult to detect and clean up. Oil remains a pollution at sea for a long period and the continuous low-level discharge has the potential to disturb a variety of ecosystems for years to come. Steps have been taken to prevent oil pollution from shipping, including the International Convention for the Prevention of Pollution from Ships (MARPOL), which is a comprehensive and technical convention that can be amended to further increase its efficacy.
Environmental pollution and degradation has, in recent times, become an area of concern for many worldwide. This is due to increasing awareness of the potentially detrimental effects of environmental pollution. The current state and extent of environmental pollution is alarming and is a major cause for concern. The unrelenting pace of modern development has resulted in a burgeoning increase in the types and quantities of pollutants released into the environment. Chief culprits are the many different kinds of industry and transportation. This includes the maritime transportation of goods and materials. While it is generally an eco-friendly form of transport, the huge amount of cargo vessels plying the oceans also makes it potentially a significant source of marine pollution.
1.1 Background of ship collisions with cargo vessels
The environmental impact of ship collisions comes in many forms, ranging from fresh paint fouling of a new ship to the release of noxious substances, debris, and culminating in the potential catastrophic release of oil. This point makes ship collision a particularly high-risk activity; even a small-scale collision can have drastic repercussions. The shipping of noxious substances and oil is a high-consequence, high-probability event when it comes to ship collisions. A study was conducted by Hossain and Islam on the probability and impact of MARPOL Annex I and II oil spills caused by tankers worldwide. They used a quantitative risk assessment to show that the probability of occurrence of an oil spill in shipment is very high, and regions with high oil production and transport are at greatest risk (e.g., the Gulf of Mexico, North Sea, Mediterranean, and the Caribbean).
Ship collisions with cargo vessels are a global issue that has been increasing with the rapid growth in seaborne trade. The number of ships in oceans around the world is increasing, and therefore there is a higher probability that ships will collide. Derelict and semi-submerged ships are particularly hazardous to modern ships. They are difficult to detect on radar, and there is often little warning of their presence. Ships are also designed to travel at faster speeds these days, therefore there is a higher chance that a collision with an obstacle in the water will occur. An increase in the magnitude and frequency of ship collisions will result in larger economical and environmental impacts. The 1989 Exxon Valdez oil spill was one of the most publicized and studied ship pollution incidents, yet there are hundreds of ship collisions that result in oil spills into the ocean every year.
1.2 Significance of studying the environmental risks
The environmental consequences of ship collision incidents are numerous and far-reaching. The potential risks to the environment are great and include the direct consequences of a ship sinking or remaining afloat and releasing oil or other hazardous materials. These can have both immediate effects and long-term chronic effects. There are also many indirect consequences to the environment. The cost of a ship collision incident is difficult to determine and is often underrepresented in comparison to the true cost to the environment. This is due to the complexity and diversity of ecosystems and the interaction of the various affected components. Often the effects of a ship collision incident are unique to the specific location and conditions at the time of the accident. Environmental responses and recovery can require long-term mitigation management, habitat restoration or enhancement, and the cost of this is generally far greater than the original damage. The international law of the sea is predominantly geared to the protection of human interests and is often insufficient for dealing with the complexity of environmental issues and the protection of various affected resources. Because ship collision incidents are frequent yet variable events, it is difficult to quantify their specific and potential risks to the environment using past incidents or modeling techniques. This requires a more in-depth understanding of the processes and effects of ship collision incidents and the development of assessment methods specifically geared to environmental risk.
1.3 Purpose and objectives of the research
The primary purpose of this research is to comprehensively identify the environmental risks resulting from ship collisions involving different classes of vessels. This will provide a sound foundation for future studies on evaluating the management of these identified risks, and an understanding of the types of marine casualties likely to result in environmental damage. In order to achieve this goal, the research will assess the environmental risks resulting from ship collisions involving four different classes of vessels. This would be accomplished using several methodologies including past trend analysis of collision data, a Delphi analysis on the likely environmental impacts of specific collision scenarios, and analysis of the current and potential future damage mitigation measures for shipping and its effects on the environment.
The research will be the first to identify the specific types of shipping incidents and the vessels involved which are likely to result in environmental damage. This is significant as it will assist in recognizing the areas of greatest risk to the environment and help stakeholders to decide on the most prudent measures for serving the common good. This will provide an informed basis for maritime policy and decision makers wanting to avoid practices that would be detrimental to the environment, including an evaluation of the trade-offs between different types of shipping activities and the costs involved with reducing the risk of environmental damage from ship collision.
2. Types and Causes of Ship Collisions
There are three types of ship collisions, with each different type becoming increasingly more serious in terms of the risk of potential collision. A head-on collision occurs when two vessels are approaching each other “head on” and there is failure in the right-of-way regulations (explained later). This type of collision is the most serious as both vessels are on a constant bearing, which requires drastic alteration of course from one or both vessels to avoid the risk of collision. A slight or substantial error in judgment or a problem in communications, the required alteration of course or the actual passing of the other vessel, results in a collision. A side-sweep collision occurs along a vessel’s side. This collision is less serious than a head-on collision since the probability of success in transitioning from collision course to parallel course is decent. However, once the risk of collision is perceived to have been overcome, it is not uncommon for the vessel at fault to have acted to draw its vessels across the bow of the innocent vessel, thus turning the side-sweep collision into a T-bone collision. A T-bone collision got its name from the similarity of the vessel collision to a T-bone car accident. This type of collision is attributed to its an indication of its severe risk and potential damage to both vessels involved. Typically, T-bone collisions happen due to right-of-way violations or failure to adhere to traffic separation schemes. When at the base of all collision types, the root of the problem is due to the lack of skill in the manoeuvring of vessels and trying to avoid a situation with as little change to the present course or speed of the vessel to resolve the risk of collision.
2.1 Collision types: head-on, side-swipe, T-bone
There are three primary types of vessel collisions, categorized by the position of the striking and struck vessels. Drifts and Hughes identified these as head-on, side-swipe, and T-bone collisions. Analysis of collision dynamics will examine each of these in turn, as the damage caused depends on the relative headings and speeds of the two vessels. In a head-on collision, the two vessels are travelling on reciprocal courses that will result in impact. Damage will be simplified and the risk of pollution is limited. Far more serious are T-bone collisions where the striking vessel is at right angles to the other. This can result in penetration of the hull or striking the vessel broadside or stern causing severe damage and risk of pollution. Side-swap collisions are the most common and result from an error in the crossing situation whereby each vessel takes avoiding action in the same direction thereby causing follows an intended.
2.2 Factors contributing to ship collisions
The factors that lead to ship collisions are still poorly understood, largely due to a lack of detailed information about the circumstances of individual incidents. Factors can be very varied, and difficult to disentangle from one another. One approach to understanding them is to consider the necessary conditions that must be met for a collision to occur. According to Newton’s second law of motion, the critical condition is that the rate of change of momentum of one, or both, of the colliding ships, with respect to the other, is not equal to zero. This can occur if a ship alters its speed or course such that it moves across another ship’s path, or stops, or fails to respond to changes in the movement of other ships. In a similar vein, sufficient relative movement between two ships is also a necessary condition for collision, such as when one ship drifts or is set onto a dangerous course by wind, current or tide. These necessary conditions can be considered in conjunction with a range of other, more specific factors. An extensive study of collisions between fishing vessels off the south coast of Ireland identified the following common sequence of events. An overtaking vessel alters course to starboard to pass ahead of the vessel being overtaken. Due to confusion or misunderstanding, the two vessels alter course to pass each other on the same side. The inside vessel is unaware of the presence of the outside vessel on its inside quarter because it is in the blind sector of the inside vessel’s only deck-mounted radar. This sequence has clear similarities with the “rules of the road” situations regarding overtaking and meeting head-on and suggests that failure to adhere to these rules is a common factor in many collisions.
2.3 Common causes of ship collisions
• Violation of rules of navigation.
• This is one of the oldest causes. There are various rules of navigation at sea for the purpose of prevention of collision. Ignorance of these rules or more often than not neglecting these rules and regulations lead to collisions. Such rules are made by international conventions and agreements and are mostly based upon general principles of good seamanship. An example of this cause would be when the vessel was on the port side of the stand-on vessel where the rules stipulate that vessels on the port side of the other are to keep out of the way of the stand-on vessel but due to lack of understanding of these rules two vessels would try to do the same thing. Any confusion over what to do in the situation can prove dangerous.
• Poor lookout.
• Many collisions occur during fair weather or clear visibility. This is not related to environmental causes but more so due to vessel personnel being complacent in the belief that there is no other traffic around. This is mostly the case with a large number of pleasure craft operators. A lookout by sight and hearing as well as by all available means appropriate to the prevailing circumstances and conditions so as to make a full appraisal of the situation and the risk of collision is a requirement of the International regulations for preventing collisions at sea (1972). This is not complied with in many situations where the officer on duty believes that nothing should be wrong within the time he leaves the bridge until his return. Such a belief in itself is erroneous and can be a cause of collision.
3. Environmental Impacts of Ship Collisions
The release of oil can have devastating effects on the marine environment and on coastal areas. Oil can persist in sediments, releasing hydrocarbons over a long period, and cause damage to benthic fauna and flora. It can have fatal and sub-lethal effects on organisms at all levels in the marine environment, from plankton to large mammals. It has been shown to cause a range of effects on fish. For example, the early life stages of many fish species can be particularly sensitive to oil pollution. Oil can also have negative effects on birds and mammals through oiling of their feathers or fur, which can result in hypothermia, increased risk of drowning or death, and it can have long-term effects on the reproductive capabilities of the individual. Finally, oil pollution can cause damage to areas of special conservation or historic interest and harm industries such as aquaculture and fisheries.
The environmental impacts from ship collisions are quite complex. The release of oil and chemicals and the physical destruction caused by the ship can lead to a wide range of impacts. The release of oil resulting from a collision or running aground can have the most devastating effect on the environment. Unlike the release of oil from a tanker, which occurs mostly offshore, the release of oil from groundings and collisions is usually in or near coastal waters. It can have a wide variety of effects, depending on the type and quantity of oil released and the characteristics of the area affected. Car engine oil and diesel are also known to cause havoc to the environment. For example, the release of 5 tonnes of diesel from a cargo vessel that ran aground at the entrance to the Firth of Forth, near Edinburgh, caused pollution of bird populations, loss of several species of marine life, and it continues to affect the local economy which relied on fishing.
3.1 Oil spills and pollution
Shipping activities are particularly prone to causing oil pollution in the marine environment. Compared to oil tanker accidents, which have the potential to cause catastrophic oil spills, the quantity of oil spilt in individual incidents involving cargo ships may be smaller, but can still have serious effects. This is due to the fact that oil is carried as fuel for the vessel in addition to the lubricating oils for the engine, and the damage from oil spillage can be longer lasting than the structural damage and subsequent release of cargo. Oil is toxic to marine organisms, often being lethal on contact. Light oils can persist in the marine environment for decades, in some cases still being a hazard to wildlife and sea bed communities. Due to the variety of ways oil can affect the marine environment as a pollutant, it is considered one of the most dangerous substances to the marine environment. Oil is also one of the hardest substances to clean up from an affected environment and costs of oil spill clean ups in the past have been substantial. Usually the costs of damage to an affected environment or losses in the fishing industry have been far greater than the costs of clean up. Oil spills from ship accidents can have dramatic effects which are readily apparent in the short term such as dead and oil-covered sea birds or marine mammals, but there are also more subtle long-term effects which may not be noticeable but can cause damage to affected environments such as smothering of sea grass beds and soft sediments.
3.2 Damage to marine ecosystems
Damage to marine ecosystems can be caused by many factors stemming from ship collisions, including the introduction of toxic substances or the actual destruction of environments. The extent of damage is usually dependent on the severity of the spill, the type of ecosystem affected, the animals and plants present, and the intensity of the cleanup operation. Oil spills can have a detrimental effect on marine ecosystems. Oil tends to float on the water’s surface and becomes mixed by water and wave action, making a sticky, toxic substance that can persist in the environment for months or even years. Oil coats everything that it comes into contact with and can cause chronic and often fatal health problems in organisms. It is often lethal to marine mammals and surface-dwelling creatures, which can die from acute exposure. Sea otters and birds are the most famous victims of oil spills. A light coat of oil on the feathers of birds and fur of otters can destroy the insulating ability, and the animals can die from hypothermia during cold weather. High-profile events such as large oil spills create media attention and raise awareness of the severity of oil pollution and its ongoing effects. This can be seen from the Oil Pollution Act, whereby double-hulled tankers were required to prevent spills such as the Exxon Valdez from occurring. Other areas of prevention include international legislation.
The actual destruction of ecosystems resulting from ship groundings can occur as a result of impact or through the smothering effects of oil. Physical damage takes the form of scouring the substrate, removal of vegetation, and in the worst case, total habitat destruction. Shallow subtidal soft bottom communities are extremely vulnerable to the effects of ship groundings due to their proximity to shipping lanes and high-use areas. Damage occurs when ships run aground, as propellers create furrows and holes in the substrate, and the turbulence dislodges and removes organisms from the sediment. This has been seen in a number of ship groundings, one of the most famous being the grounding of the MV Braer in Shetland, which resulted in the spillage of 84,500 tonnes of light crude oil and an 11-mile-long slick, severely damaging the area of Garth’s Ness and continuing to have effects on the environment today. In deep water, oil spills can sink to the seafloor, and with the marine environment being heavily influenced by vertical flow processes, the effects on the seafloor can be significant. An example of this would be the Torrey Canyon, which spilled 25-36 million gallons of oil off the Isles of Scilly, with continued effects being seen on the marine environment today.
3.3 Threats to marine wildlife
As with terrestrial animals, the main impact of a ship collision on marine wildlife is direct mortality, from being hit by the ship or from injury caused by the collision. These impacts may affect populations of marine mammals, sea turtles, and large fish species which may be killed outright or sustain injuries that affect their survival and reproductive success. Effects on populations of large, long-lived species may have considerable implications for the structure and functioning of marine ecosystems. Available information on collision-related mortality of marine animals is sparse, largely confined to reports of specific incidents or to the activities of individual researchers. There have been few attempts to quantify the global extent of the problem and little attention has been directed to improving the situation. However, a preliminary assessment of the risk of a number of potential threats to marine wildlife in the North-east Atlantic (including ship collisions) conducted by the Natural History Museum for the Joint Nature Conservation Committee estimated that the risk of ship collisions for marine turtles was medium to high. This assessment was based on the distribution of marine turtle species and the density of ship traffic in areas where turtles occur.
4. Mitigation Strategies and Future Outlook
4.2 Technological advancements for collision prevention
As the world becomes more dependent on electronic navigation systems, there is a danger that the standards of watchkeeping on the bridge of some vessels will be lowered. A full appraisal of the role and effectiveness of the collision regulations in meeting the needs of modern ship operation and in preventing collisions is required. The correct use of radar by ships is one of the main aids to collision avoidance, and so ships of 300 tons and above must have a radar system.
Radar has been teamed with vast advances in computer technology and aided by devices such as Automatic Radar Plotting Aids (ARPA). More recent advances in satellite technology have led to the development of the Global Positioning System (GPS), which is a set of satellites and receivers with the ability to determine the exact position of a ship anywhere in the world. This knowledge has led to the development of Electronic Chart and Display and Information Systems (ECDIS), which is an automated navigation system that uses electronic navigational charts and integrates position information from the GPS with information from other onboard sensors such as log and depth devices.
International regulations and guidelines
Only after World War I, countries began to consider the need to develop international regulations on ship safety. This led in 1914 to the 1st Safety of Life at Sea Convention (SOLAS) convened in London and further safety requirements for tankers. The most significant worldwide measure to improve safety at sea is provided by the International Convention for the Safety of Life at Sea (SOLAS), which requires flag states to ensure that ships comply with functional requirements. It was first adopted in 1974 and it entered into force in 1980, setting out international minimum standards for the construction, equipment, and operation of ships.
4.1 International regulations and guidelines
The regulations and guidelines, provisions that are directives to achieve an objective. They are action oriented and are addressed to specific sectors, aiming to prevent and control marine pollution coming from ships, minimize the risk of damage to the coastal and marine environment as a result of a ship’s operations in a port or its approach procedures, reduce air pollution and GHG emissions from ships, and manage the transfer of invasive aquatic species in ballast water and biofouling. After a series of meetings and discussions, the Marine Environment Protection Committee adopted the “Final Act of the Conference the International Convention for the Prevention of Pollution from Ships, 1973, as modified by the Protocol of 1978” on 17 February 2004, which was henceforth called MARPOL 73/78. This covered comprehensive aspects of marine environment protection including prevention of pollution, air pollution, and prevention of damage to the marine environment. The International Convention for the Control and Management of Ships’ Ballast Water and Sediments was adopted intending to prevent and control the introduction of invasive aquatic species and bioinvasion by establishing standards for discharge and treatment, exchange of ballast water and sediments management. Ships today are highly reliant on electronic navigation systems. In view of this, the International Convention for the Safety of Life at Sea, specifically Chapter V, has defined the requirement for an Electronic Chart Display and Information System (ECDIS) as a navigation tool which is designed to enhance safety, and the IMO resolution MSC.86(70) removed paper charts as a back-up option, making ECDIS essential to ships in the future. This will reduce the problem of navigational errors caused by geographical or hydrographical uncertainties of uncharted potential hazards. Collectively, the regulations and guidelines that have been or will be taken in the future are designed to specifically reduce the risk and damage caused by ship collisions with cargo vessels to its surrounding environment.
4.2 Technological advancements for collision prevention
The technological advancement of Electronic Navigational Charts (ENC) for precaution to shipping routes in potential navigational risk areas is a positive move for collision prevention. The system enables the ship navigators to program a route using the best available information to display the route to be taken and the associated navigational hazards. The system could be used to develop routing measures where areas with a high probability of risk could be avoided using the ENC to analyze port entry and approaches to identify areas of potential risk within the local area. This concept had been developed further by UKC Management project which is developing and testing a software tool that uses data stored in digital GPS based ships to predict and thus avoid potential collisions. It is still an ongoing strategy to prevent ship-ship collisions but it is a positive development in that it will identify high-risk areas and with the ability to avoid potential collisions.
Another technology under development using modern knowledge management techniques is the development of Intelligent Awareness Decision (IADS) support system designed to ensure that bridge teams are maintaining an optimal state of situational awareness. This is an important development since it is lack of situation awareness due to poor decision making that is involved in 80% of incidents. IADS supports prediction and safety risk assessment through constant monitoring and reporting of the user’s assessment of the situation and proposing alternative action when a high-risk situation is identified. This concept shares similarities with the aviation industry’s Crew Resources Management training for incident prevention.
In recent times the automatic identification system (AIS) has become a valuable tool for collision prevention by allowing the monitoring, identification and exchange of vital information regarding the vessel’s identity, position, course, speed, navigational status and other safety-related information with other nearby ships and Vessel Traffic Services (VTS) stations. AIS has accelerated the practice of ship to ship route crossing encounters using the give way vessel and the stand on vessel by providing immediate identification of position and heading of the other vessel and the likelihood of a close quarters situation so that rapid and better-informed decisions can be made.
4.3 Future prospects and challenges in reducing ship collisions
One solution to reducing the risk of collision may be in reducing the overall number of ships at sea, particularly in high risk areas. Whilst the trading demands of the modern global economy make this an unlikely prospect, the growth of air freight and continued efforts to reduce stockpiling of oil with increased production and refining on an as needed basis may see a slow reduction in certain high risk shipping activities. Energy efficiency gains in shipping may also lead to a reduction in the operational speed of certain vessel types. This would generate mixed results; reducing the kinetic energy and thus consequences of a collision, but increasing the time reaction time of some collisions and placing heavier demands on crews to maintain effective situational awareness.
Despite the protective effect of the measures that have been taken to date, the projected increase in world trade coupled with the large number of highly populated narrow seas indicates that the risk of collision is likely to remain high. The growth of international shipping penetration in all ocean areas also means that the risk of teething problems with new technology increase and that in some cases, complicated cost effective solutions will have to be found whereby the level of risk is not increased. With very few new ships being constructed for operation in isolation, the impact of increasing automation and technology in collision avoidance systems will be slow to influence the risk for existing vessels.

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