Coastal Engineering

Summary

Coastal engineering is a branch of engineering that aims to solve coastal zone problems such as shoreline erosion and the destruction caused by tsunamis through the development, construction, and preservation of mechanisms and structures. Coastal engineering also entails understanding the theories and processes of wave actions and forces, ocean currents, and wave-structure interactions. Given that coastal areas are often highly populated and especially vulnerable to human impact, coastal engineering attempts to blend conservation and management of the world's coastal zones with the development requirements of humans.

Definition and Basic Principles

Coastal engineering is a branch of civil engineering involved in the development, design, construction, and preservation of structures in coastal zone areas. Its primary function is to monitor and control shoreline erosion, design and develop harbors and transport channels, and protect low-lying areas from tidal flooding and tsunamis. To achieve such objectives, coastal engineers must have a strong understanding of the sciences of engineering, oceanography, meteorology, hydrodynamics, geomorphology, and geology. They must also have a strong understanding of the theories and processes of wave motion and action, wave-structure interaction, wave-force forecasting, and ocean current prediction.

Coastal areas are socially, economically, and ecologically crucial. They are home to a significant proportion of the world's human population, serve as important breeding grounds for many animal species, and are important for tourism, aquaculture, fishing, transport, and trade. These multiple uses of a relatively small area have led to rapid environmental degradation and have created conflict and the need to achieve a sustainable balance.

Background and History

Although the specialty of coastal engineering emerged only in the latter half of the twentieth century, the ideas of coastal engineering and management have been practiced for centuries. Humans have long lived in coastal zones and attempted to control and manage the effects of tidal flooding and wave action and to engage in land reclamation. People have developed ports to make transportation and trading easier. The first riverport was built on Egypt’s Nile River before 3000 BCE. The first coastal port was built on Pharos near Alexandria in about 2000 BCE. For centuries, many countries wanting to protect strategic coastal areas used structures such as embankments as sea defenses.

Early engineering projects mainly involved hard coastal engineering—designing and building docks, ports, defenses, and walkways. Although coastal engineering has long been practiced, the actual coastal processes and their driving forces were little understood. Therefore, formal engineering development requires much more comprehensive knowledge of the ocean and the processes and principles involved.

Traditionally, engineering projects in coastal zones were the province of civil and military engineers. However, because of the growing need for specific research in coastal engineering, the first International Conference on Coastal Engineering was held in 1950 in California, establishing the branch of applied science and introducing the terminology. The conference proceedings stated that coastal engineering was not a novel science or unconnected to civil engineering but rather was a branch of civil engineering that was strongly reliant on and influenced by sciences such as oceanography, meteorology, electronics, and fluid and structural mechanics.

By the 1960s, significant inroads had been made into understanding coastal processes, and this, coupled with advances in modeling, highlighted the importance of incorporating such processes into design and construction. By the 1970s, an increased understanding of coastal processes led to the introduction of soft coastal engineering, including beach nourishment and artificial dunes. In the following decades, significant progress was made in developing coastal engineering techniques, such as modeling techniques for deep-water wave prediction, and understanding processes, including wave-structure interaction and coastal sediment erosion.

Essentially, coastal engineering has transformed from a science that simply responds to anthropocentric demands (docks, ports, and harbors) to one that aims to balance human requirements and environmental protection, with a particular focus on mitigating natural and human-induced coastal erosion.

How It Works

It is the job of a coastal engineer to recognize the characteristics and natural processes of the shoreline environment and to apply fundamental engineering theories and philosophies to solving ecological problems. To be successful, a coastal engineer must have a strong understanding of other sciences such as oceanography, meteorology, geomorphology, structural and fluid mechanics, and hydrodynamics. In particular, this means clarifying and using theories of wave action, wave-structure interaction, wave-force forecasting, ocean current prediction, and beach profile modification.

Coastlines across the world are the natural division between the terrestrial landscape and the seas and oceans. The geological composition of these areas is distinctive, as are the natural and anthropomorphic processes that affect them. Coastal engineering techniques must consider the morphological development of coasts, such as erosion and accretion, and relate this to shore protection through engineering approaches and structures.

The action of waves on the shoreline forms one of the fundamental areas of coastal engineering research. Waves contain a very large amount of energy formed by the action of wind over vast tracts of open water, the gravitational attraction of the Sun and Moon, and occasionally seismic activity (as with tsunamis). Although this energy is collected over very large areas, it is released along relatively small areas of coastline. This release of energy, in the form of breaking waves, strongly influences coastal areas’ sediment and geological structures. The shoreline or beaches, frequently composed of sediments such as sand, shingle, or gravel, are constantly battered and reshaped by the wind and water.

Erosion is a natural process, and the movement of sediment is achieved by wave uprush, which transports sand onshore, and backwash, which transports sand offshore. The natural erosion process in coastal areas is very complex and involves flow fields created through the action of breaking waves and erratic turbulent sediment transport in the water column and a shifting shoreline. Worldwide research aims to develop predictive models of this erosion process. Over time and under normal conditions, erosion is also a relatively cyclical process. Sediment can be carried offshore during one season and dumped back onshore during the next season and moved obliquely along the shore over time. Erosion processes can, however, be significantly disrupted by human activity and structures or can be considered undesirable because of human requirements and desired aesthetics. Coastal engineering structures can be both detrimental and beneficial concerning coast erosion, and most coastal engineers believe that only an integrated and holistic approach to planning and design can generate long-term sustainability.

Within this energetic and process-driven natural boundary between land and sea, people have constructed coastal engineering structures such as ports and harbors, which have had positive and negative effects on the environment. The design of such structures must predict wave dynamics and their impact on individual coastal zones and beach environments. Since the emergence of coastal engineering science, much greater emphasis has been placed on understanding coastal processes, such as wave action, and designing and developing policies and structures to protect coastal areas from erosion.

Although the study of coastal erosion is a fundamental concept for coastal engineering, coastal engineers must also recognize and study coastal protection measures and applications such as hard and soft shoreline protection structures, understand the effects of these structures on the morphology of the coastal areas, and develop effective coastal zone management plans and policies.

Applications and Products

Coastal engineering structures and activities vary significantly from country to country. They depend on social aspects, such as the country's history and development and its people's relationship to the ocean, and environmental and structural aspects, such as the nature of the ocean along the country's coast, geomorphological and geological conditions, the ecosystem, climate, extent of tectonic activity, currents, and wave action.

Generally, there are two types of coastal engineering applications—hard and soft coastal engineering. Although hard stabilization techniques have been used for many years and are considered appropriate under certain circumstances, they can also be expensive and can disrupt and destroy natural shoreline processes and habitats, intertidal areas, and wetlands. In some cases, they can even increase erosion. As coastal engineering has evolved and become more sophisticated, engineers have moved away from constructing hard structures with little understanding of their impact on the environment and toward incorporating soft engineering and minimizing the ecological impact.

Hard Structures and Applications. Groins are solid structures, usually constructed from wood, concrete, or rocks, running perpendicular from the foreshore into the water (under normal wave levels). They aim to disrupt water flow and reduce the transportation of sediment from longshore drift. They trap sediment to extend or preserve the beach area on the up-drift side and reduce erosion on the down-drift side. The size and length of these structures are usually determined based on specific local conditions, including wave dynamics, beach slope, and environmental factors. Seawalls are large, rigid, and usually vertical structures constructed from concrete. They are found at the transition between the low-lying beach and the higher mainland and run parallel to the shoreline. The main function of a seawall is to preserve the shoreline by preventing additional shoreline erosion and recession during direct wave-energy impact and flooding. Seawalls are, however, not effective in preventing longshore erosion.

Revetments are a concrete, rock, or stone veneer, or facing, constructed on a beach slope to prevent erosion caused by wave action and storm surges. Unlike seawalls, which can assist in flood prevention, revetments are not usually constructed for this function. Revetments are always built as sloping structures, and although they may sometimes be completely solid and rigid, they are often built with interlocking slabs or stone and designed to be permeable. This permeability tends to enhance the strength of the revetment and the absorption of wave energy while reducing erosion and wave run-up. Revetments can also be made from sand-filled bags, interlocking tires, concrete-filled bags, and wire-mesh stone-filled gabions (sunken cylinders filled with earth or stones). As revetments tend to be passive structures, their application is often limited to areas already protected in some other way or by some other engineering structure.

Breakwaters are fixed or floating structures built parallel or at an angle to the shoreline. The main function of a breakwater is to protect the shore and activities along the coastline by reducing the impact of wave energy. The ability and impact of a breakwater depend on whether it is submerged or floating, its distance from the shoreline, its length and orientation, and if it is solid or segmented. The four main types of floating breakwaters are box, pontoon, mat, and tethered float. The three main types of detached breakwaters are offshore, coastal, and beach.

Soft Structures and Applications. Shore nourishment has become one of the most common soft coastal engineering applications. The three main types are backshore, beach, and shoreface nourishment. As the name suggests, nourishment involves artificially adding sand to the backshore (upper part of the beach), beach, or shoreface (usually the seaside of the bar) attempting to modify the effects of erosion. Although nourishment replaces sand in an eroded area and is considered a rather natural form of coastal engineering, it does not address the causes or processes of erosion or reduce the impact of wave energy.

Sand dune stabilization is a relatively basic and common form of soft coastal engineering. It involves planting vegetation to stabilize and protect dunes along the coastline. Creating artificial dunes is also considered an effective form of soft coast engineering protection, particularly in conjunction with shore nourishment.

Beach drainage, or beach dewatering, is a system of shore protection based on the concept of physically draining water from a beach. Drainpipes are installed and buried below the beach and parallel to the shoreline. These pipes collect seawater and transport it to a pumping station, where it is collected and either returned to the ocean or used. Beach drainage helps reduce erosion by lowering the water table in the uprush zone and reducing the force of the backwash by increasing the volume of water that seeps into the beach.

Careers and Course Work

Many universities offer undergraduate and graduate degrees in coastal engineering. Most commonly, students who wish to pursue a career in coastal engineering will study engineering or marine science as an undergraduate. By graduation, students should have a solid understanding of coastal engineering concepts, theories, processes, and practices, such as wave action, wave transformation, statistical and numerical analysis, tides and currents, beach dynamics and coastal structures, and the impact of natural and anthropogenic factors on the coastal environment. In addition, as coastal engineers need to provide the scientific base data used for coastal zone management, they require knowledge and experience in using modeling.

Students who study coastal engineering can enter such careers as consulting engineers, project managers, environmental consultants, and construction contractors and such fields as construction management, coastal and oceanographic engineering, water resource management, and hydrologic engineering. They may find employment in the private sector, with nongovernmental organizations, with specialized government organizations and agencies, or in universities undertaking teaching and research.

Social Context and Future Prospects

The social, economic, and ecological consequences of coastal erosion are significant. Almost 60 percent of the world's population lives within 100 kilometers of a coast. Coastal areas provide significant economic benefits—fish and other maritime products, a means of transportation, and easier access to trading partners—and numerous recreational opportunities. However, the economic and aesthetic appeal of coastal areas has created population pressure that has greatly increased the need for functional coastal structures, such as ports, wharfs, and jetties, and infrastructure, such as roads and sewerage facilities, which increase erosion and pollution. The erosion caused by human activities and structures can change beach dynamics and profiles, which can have ecological effects, such as the loss of animal breeding grounds, and social effects, such as making the area unsafe for swimming.

Research and climate change modeling has indicated that sea levels may rise significantly in the twenty-first century. This, coupled with an associated increase in coastal storm frequency and strength, will produce more floods and greater erosion, creating serious ecological repercussions for the coastal zones of the world, which are often densely populated and popular areas for tourism. The construction of such engineering structures as ports, harbors, recreational facilities, and resorts is necessary for continued economic and social development. Such engineering has, however, a significant ecological impact on the coastal zone areas, particularly an increase in erosion. One of the primary goals of coastal engineering is to rectify erosion issues.

The difficulty for the future of coastal engineering is that some of the solutions to such environmental or aesthetic issues can be ineffective or ecologically unsound, exacerbating the problem. As such, the future of coastal engineering requires integrated coastal zone management (ICZM), a holistic and integrated strategy and approach incorporating hard and soft engineering for managing all aspects of coastal areas. It incorporates advances in modeling that help develop a framework for predicting coastal erosion hazards and processes. Many coastal engineers advocate an integrated approach, stating that the future ecological and economic sustainability of the world's fragile and vulnerable coastal areas depends on its adoption. Such a strategy is optimal, as it considers issues like climate change, sea level rise, navigational needs, the impact on plants and animals, and aesthetic considerations.

Further Reading

Dean, Robert G., and Robert A. Dalrymple. Coastal Processes with Engineering Applications. 2002. Cambridge UP, 2004.

Jha, Ramakar, et al. River and Coastal Engineering: Hydraulics, Water Resources and Coastal Engineering. Springer, 2023.

Kamphuis, J. William. Introduction to Coastal Engineering and Management. 3rd ed. World Scientific, 2020.

Kraus, Nicholas, ed. History and Heritage of Coastal Engineering: A Collection of Papers on the History of Coastal Engineering in Countries Hosting the International Coastal Engineering Conference 1950–1996. American Society of Civil Engineers, 1996.

Reeve, Dominic, Andrew Chadwick, and Christopher Fleming. Coastal Engineering: Processes, Theory and Design Practice. 3rd ed., CRC Press, 2018.

Shibayama, Tomoya. Coastal Processes: Concepts in Coastal Engineering and Their Application to Multifarious Environment. World Scientific, 2009.

Sorensen, Robert. Basic Coastal Engineering. 3rd ed. Springer, 2006.

Young, Kim. Handbook of Coastal and Ocean Engineering. World Scientific Publishing, 2018.