Coastal Protection Hard Engineering | A Level Geography Note

Hard engineering, also known as structural measures, refers to the use of man-made structures to protect coastlines from erosion and flooding. These structures include seawalls, breakwaters, groins, and jetties.

Hard engineering is often used as a solution to coastal erosion and flooding, as it can provide immediate protection and is relatively straightforward to implement. However, this approach can also have negative impacts on the coastal environment, including the alteration of natural sediment transport patterns and the loss of habitats for coastal wildlife. Studies have shown that a combination of hard and soft engineering approaches may be more effective in managing coastal erosion and flooding over the long-term.

The main focus of this article will be on hard engineering and explain the method of operation, advantages, and disadvantages.

Differentiating Hard and Soft Engineering in Coastal Protection

Hard engineering refers to the use of man-made structures, such as seawalls, breakwaters, groins, and jetties, to protect coastlines from erosion and flooding. This approach is often used as a solution to coastal erosion and flooding, as it can provide immediate protection and is relatively straightforward to implement. However, hard engineering can also have negative impacts on the coastal environment, such as altering natural sediment transport patterns and loss of habitats for coastal wildlife.

Soft engineering, on the other hand, focuses on natural solutions to coastal erosion and flooding, such as beach nourishment, dune restoration, and the use of vegetation. This approach aims to mimic natural processes and can be more sustainable in the long-term, as it allows for the natural dynamics of the coast to continue. However, soft engineering can be less effective in providing immediate protection and may require more maintenance.

A combination of hard and soft engineering approaches may be the most effective in managing coastal erosion and flooding over the long-term.

What are the Techniques of Hard Engineering?

As briefly touched on above, hard engineering techniques for coastal protection include the construction of structures such as seawalls, breakwaters, groins and jetties. Before we dive into the details of each kind and provide examples, here’s a brief explanation: Seawalls are vertical walls made of concrete, steel or stone, built along the shoreline to hold back the sea and protect the land behind it. Breakwaters are structures built in the sea that protect the coast from the force of waves, they can be constructed in different forms like submerged, semi-submerged, and detached. Groins are small walls perpendicular to the beach that trap sand and prevent longshore drift and erosion. Jetties are structures built on the river mouths and at the entrance of harbors to control the flow of sand and sediment and protect the navigation channel. These structures can provide immediate protection against coastal erosion and flooding, but they can also have negative impacts on the coastal environment, such as altering natural sediment transport patterns and loss of habitats for coastal wildlife.

Ocean Walls

An ocean wall, also known as a seawall, is a man-made structure built along the shoreline to hold back the sea and protect the land behind it. They are typically made of concrete, steel or stone and can be built at various heights, depending on the level of protection needed. Seawalls can be effective in protecting coastal areas from erosion and flooding, but they can also have negative impacts on the coastal environment. For example, seawalls can disrupt natural sediment transport patterns, leading to erosion elsewhere along the coast. They can also alter the natural beach profile and negatively impact coastal habitats for wildlife.

The Great Wall of seawall in the Netherlands, called Afsluitdijk, is a well-known example of an ocean wall. It is a series of dikes and dams that protect the low-lying Netherlands from the North Sea. The wall stretches for over 500 kilometers along the coast and is up to 32 meters high in some places. It was built in stages over several centuries and has been continuously strengthened and modernized to protect the country from flooding. The wall has been successful in preventing coastal flooding, but it also has negative impacts on the coastal environment, such as altering natural sediment transport patterns and reducing the availability of habitats for coastal wildlife. Additionally, the wall is not able to protect against a very large storm surge, and thus the Netherlands have been working on different types of coastal protection measures like beach nourishment and dune restoration, to reduce the risks of flooding.

Satellite image showing a sea wall, Afluitdijk, in the Netherlands

Afsluitdijk with the Wadden Sea, Netherlands

One example of an ocean wall in the United Kingdom the sea wall in Ventnor on the Isle of Wight, England. It is a coastal protection structure that was built to protect the town of Ventnor from coastal erosion and flooding. The wall stretches for approximately 800 meters along the coast and is made of reinforced concrete. It was built in the late 19th century, and it has been continuously strengthened and modernized over the years to protect the town from the sea. The wall is designed to dissipate the energy of waves and slow down coastal erosion by creating a stable surface for sediment to accumulate.

The sea wall in Ventnor has been successful in protecting the town from coastal erosion and flooding, but like many coastal protection structures, it also has negative impacts on the coastal environment. The wall disrupts natural sediment transport patterns, leading to erosion elsewhere along the coast. It also alters the natural beach profile and negatively impacts coastal habitats for wildlife. Additionally, the wall is not able to protect against a very large storm surge, and thus the town is planning to upgrade it in the near future.

An example of an ocean or sea wall in Ventnor on the Isle of Wight, England

Revetments

Revetments are man-made structures used to protect coastlines from erosion and flooding. They are typically made of rock, concrete, or other durable materials and are constructed on top of the beach or along the shoreline. Revetments are designed to dissipate the energy of waves and slow down coastal erosion by creating a stable surface for sediment to accumulate. They can be used to protect beaches, cliffs, and other coastal areas that are vulnerable to erosion. Revetments can be an effective solution for coastal protection but they also can have negative impacts on the coastal environment, such as altering natural sediment transport patterns and reducing the availability of habitats for coastal wildlife.

Illustration showing how a revetment works in coastal protection with hard engineering

An example of revetments in the United Kingdom is along the Holderness Coast. It is a stretch of coastline in the East Riding of Yorkshire, England, that is particularly vulnerable to coastal erosion. Revetments have been constructed along the coast to protect it from erosion. The revetments are made of rock and concrete and are designed to dissipate the energy of waves and slow down coastal erosion by creating a stable surface for sediment to accumulate.

Coastal erosion along the Holderness coastline, United Kingdom, Google maps street view

Rocks being used to construct a revetment along the Holderness coastline

Coastal Barrages

Coastal barrages are large-scale coastal protection structures that are used to prevent coastal flooding. They are essentially dams that are built across a bay or estuary, and they use a combination of gates, locks and pumps to control the flow of water. Barrages can be used to generate electricity, create new habitats for wildlife, and provide other benefits. They are often built in areas that are particularly vulnerable to coastal flooding and erosion, such as low-lying estuaries and delta regions. However, barrages can also have negative impacts on the coastal environment, such as altering natural sediment transport patterns and reducing the availability of habitats for coastal wildlife. Additionally, they can also have impacts on water quality, and on the local economy, such as fishing and navigation.

One example of a coastal barrage is the proposed Tidal Lagoon Power station in Swansea Bay, Wales, UK. It is a proposed network of tidal lagoons that would use the energy of the tide to generate electricity. The project includes a barrage across the entrance of the estuary, which would have a series of turbines that generate electricity as the tide flows in and out. The project is still in the planning phase, and if built, it would be the first of its kind in the world and the largest tidal power station in the world, with a total installed capacity of over 3 GW.

The proposed project is expected to have a number of benefits, such as providing renewable energy, creating new habitats for wildlife, and providing other economic benefits. However, it also has potential negative impacts on the environment, such as altering natural sediment transport patterns, reducing the availability of habitats for coastal wildlife, and affecting water quality. The project is still under evaluation and the final decision is pending.

Artist’s interpretation of the proposed Tidal Lagoon Power station in Swansea Bay

The Cardiff Bay Barrage is a large-scale coastal protection structure that was built across the River Ely in Cardiff, Wales, UK. The barrage was completed in 1999, and it is designed to prevent coastal flooding and create new habitats for wildlife. It includes a series of locks, gates and pumps that are used to control the flow of water in and out of the bay. The barrage has created a freshwater lake in the bay, which is now used for a variety of recreational activities such as boating, fishing and bird watching.

The Cardiff Bay Barrage was a controversial project due to the potential negative impacts on the environment, such as altering natural sediment transport patterns, reducing the availability of habitats for coastal wildlife, and affecting water quality. However, studies have been conducted to minimize the negative impacts of the barrage and to ensure the sustainability of the project. The barrage also provides economic benefits, such as the development of a new waterfront area for the city of Cardiff, with new housing, offices, and retail spaces.

Rock Armour

Rock armour is a type of hard engineering used in coastal protection to dissipate the energy of waves and slow down coastal erosion. It involves placing large rocks or boulders along the shoreline to create a stable surface for sediment to accumulate. The rocks are typically chosen for their size, shape, and durability and are placed in a specific pattern to effectively dissipate the energy of waves. Rock armour can be used to protect beaches, cliffs, and other coastal areas that are vulnerable to erosion.

Rock armour is a relatively simple and cost-effective method of coastal protection, but it also has negative impacts on the coastal environment. It can disrupt natural sediment transport patterns, leading to erosion elsewhere along the coast. It can also alter the natural beach profile and negatively impact coastal habitats for wildlife. Additionally, rock armour may not be effective in areas with very high wave energy, and it may require maintenance and replacement over time.

Example of rock armour used along the San Francisco Bay shoreline

Example of rock armour used along Dawlish Warren, South Devon, England

Gabions

Gabions are baskets or cages filled with rocks or other materials that are used in coastal protection and other forms of earth retention. They are typically made of steel wire and can be used to construct walls, embankments, and other structures. Gabions are an example of hard engineering and are used to dissipate the energy of waves and slow down coastal erosion by creating a stable surface for sediment to accumulate.

Gabions can be used to protect beaches, cliffs, and other coastal areas that are vulnerable to erosion, as well as retaining walls, river banks and slope stabilization. They are a relatively simple and cost-effective method of coastal protection, but like other hard engineering solutions, they also have negative impacts on the coastal environment. Gabions can disrupt natural sediment transport patterns, leading to erosion elsewhere along the coast. They can also alter the natural beach profile and negatively impact coastal habitats for wildlife.

An example of gabions used in the UK can be found along the coast of Thropness

Groyne

Groynes are structures built perpendicular to the beach that are used to trap sand and prevent longshore drift and coastal erosion. They are typically made of wood, concrete or steel and can be built in different forms, such as parallel, perpendicular or diagonal. Groynes are an example of hard engineering and are used to dissipate the energy of waves and slow down coastal erosion by creating a stable surface for sediment to accumulate.

Groynes can be used to protect beaches, cliffs, and other coastal areas that are vulnerable to erosion. They are relatively simple and cost-effective method of coastal protection, but like other hard engineering solutions, they also have negative impacts on the coastal environment. Groynes can disrupt natural sediment transport patterns, leading to erosion elsewhere along the coast. They can also alter the natural beach profile and negatively impact coastal habitats for wildlife. Additionally, groynes may not be effective in areas with very high wave energy, and they may require maintenance and replacement over time.

Example of a wooden groyne, Mundesley, UK

Example of wooden groynes along the coast of Bridlington, England

Cliff Fixing

Cliff fixing is a method of coastal protection used to stabilize and protect cliffs from erosion. It involves the installation of anchors, cables, or other materials into the cliff face to secure loose rock and soil and prevent further erosion. The anchors are drilled into the cliff face and are connected to cables or other materials that are used to secure the cliff and prevent further erosion. It is a hard engineering method of coastal protection and is used to dissipate the energy of waves and slow down coastal erosion.

Cliff fixing can be used to protect cliffs, coastal areas and infrastructure that are vulnerable to erosion, such as roads, railroads and buildings. It is a relatively simple and cost-effective method of coastal protection, but like other hard engineering solutions, it also has negative impacts on the coastal environment. Cliff fixing can disrupt natural sediment transport patterns, leading to erosion elsewhere along the coast. It can also alter the natural beach profile and negatively impact coastal habitats for wildlife. Additionally, cliff fixing may not be effective in areas with very high wave energy, and it may require maintenance and replacement over time.

Cliff fixing to stabilise the land around Canford Cliffs, Dorset, UK

Hydroseeding and mesh to stabilise the Canford Cliffs

Offshore Reefs

Offshore reefs are a type of hard engineering used in coastal protection to dissipate the energy of waves and slow down coastal erosion. They involve the construction of artificial reefs made of rock, concrete or other materials, that are built in the shallow waters off the coast. These reefs are designed to break the energy of waves before they reach the shore, reducing the erosion and flooding caused by the waves. They can be made in various shapes and sizes, and can also provide habitats for marine life.

Offshore reefs are often used in areas with high wave energy, such as near ports, harbors, and oil and gas platforms. They can be used to protect beaches, cliffs, and other coastal areas that are vulnerable to erosion, as well as providing other benefits such as creating new habitats for wildlife, and providing recreational opportunities such as diving and fishing. However, like many coastal protection structures, offshore reefs also have negative impacts on the coastal environment, such as altering natural sediment transport patterns, reducing the availability of habitats for coastal wildlife and affecting water quality. Therefore, it’s important to consider alternative options when choosing a method of coastal protection.

An offshore reef is an example of coastal protection — Example of an offshore reef or breakwater in Portland Harbour, UK

What are the Advantages of Hard Engineering Coastal Protection?

Groynes block the wind for individuals on the seashore.
Groynes don’t influence access to the seashore.
They are generally inexpensive, and if very well kept, they can operate for 40 years.
They are a lot less expensive to fix than other hard engineering arrangements.
A wide, sandy seashore draws visitors, which brings advantages to the local economy.
An ocean divider gives individuals a feeling of well-being and security.
Ocean dividers frequently have a promenade over them, which is popular with visitors.
Ocean dividers, in general, have a long life expectancy and make substantial barriers where wave activity is vigorous.
Ocean dividers don’t hinder the development of residue along the coast by longshore drifts.
Revetments don’t block individuals from strolling along a seashore.
They are less expensive and less invasive than an ocean divider.
Less seashore material is dissolved in contrast to an ocean divider.
They are inexpensive in contrast to developing an ocean divider.
The structure is neat and straightforward to develop. It very well may be built in weeks instead of months, lessening the monetary effect of its establishment.
It is adaptable in that it very well may be set before an ocean divider, broadening its life expectancy. It can likewise be utilised to balance out slants on sand ridges.
A rock protective layer doesn’t obstruct the development of residue along the coast by longshore drifts.
They are inexpensive and simple to build.
They are cost-effective as they can last between 20–25 years.
Gabions don’t hinder the development of residue along the coast by longshore drifts.
Seashores have a characteristic appearance.

What are the Disadvantages of Hard Engineering Coastal Protection?

Groynes don’t look appealing.
Groynes are a hindrance that obstructs individuals from strolling along a seashore
The seashore on the downdrift side of the groyne can be a lot lower than the up-float side. This can make them hazardous, especially for small children. At Hornsea on the Holderness Coast, there is a height contrast of nearly 2m between the seashore on either side.
A seashore’s downdrift of the barriers causes a decrease in seashore material because of their effect on the longshore drift. This prompts expanded erosion, which has a monetary impact further along the coast.
Groynes need standard upkeep.
Groynes are insufficient during storm conditions.
Ocean dividers can influence access to the seashore.
Coastal flooding can happen when waves overtop (break over) the ocean divider.
Ocean dividers are extremely expensive to develop and maintain.
Reflected waves scour the seashore and can undermine structures.
Recurved ocean dividers can increase the erosion of seashore material.
Ocean dividers don’t look appealing.
Ocean dividers devastate living spaces for marine creatures.
Ocean dividers influence the coastal framework and lessen the contribution of residue.
Revetments can block access to the seashore.
A short life expectancy (especially when developed from wood) and unacceptable where wave vitality is high.
Revetments don’t look appealing.
Revetments demolish living spaces.
Revetments influence the coastal framework and decrease the contribution of residue.
Access to the seashore is troublesome as individuals need to move over the stone shield or make alternative routes.
Costs increase when the stone is imported.
Access to the seashore becomes difficult as individuals need to move over the stone defensive layer or make temporary re-routes.
In a harmed state, gabions are dangerous.
Gabions are limited to sandy seashores as material tossed at them on shingle seashores would rapidly degrade them.

Read more about Coastal Landscape Development

Summary

As we’ve discussed at length, hard engineering is a method of coastal protection that involves the construction of man-made structures to protect coastal areas from the effects of waves and storms. These structures, such as breakwaters, sea walls, and groins, are designed to dissipate the energy of incoming waves, reducing the amount of erosion that occurs on the shoreline.

This can be beneficial for protecting coastal infrastructure and property, as well as preserving natural habitats. Hard engineering can also be used to create new land, for example, by building artificial islands or expanding existing ones. However, hard engineering solutions can also have negative impacts such as trapping sediment and altering the natural shape of the coast. It is important to consider the long-term consequences of hard engineering solutions and to use them in conjunction with other methods of coastal protection, such as beach nourishment and conservation of natural habitats.

Frequently Asked Questions

What is coastal protection hard engineering?

Coastal protection hard engineering refers to the use of artificial structures and constructions to manage coastal erosion and protect coastal areas from flooding and wave damage. It includes measures such as seawalls, groynes, breakwaters, and offshore barriers.

How do seawalls work for coastal protection?

Seawalls are vertical structures built parallel to the coastline. They act as barriers against incoming waves, dissipating wave energy and reducing erosion and flooding in the protected area. However, seawalls can cause erosion in adjacent areas and impact natural coastal processes.

What is the purpose of constructing groynes along the coast?

Groynes are perpendicular structures built from the shoreline into the sea. They are designed to trap sediment carried by longshore currents, thereby stabilizing beaches and preventing sediment loss from erosion. Groynes can also create recreational areas and prevent longshore drift.

How do breakwaters contribute to coastal protection?

Breakwaters are offshore structures placed parallel or at an angle to the coastline. They act as barriers, reducing wave energy and providing a calm zone behind them. Breakwaters help protect harbours, beaches, and coastal developments from the direct impact of waves.

What are the potential drawbacks of coastal protection hard engineering?

Drawbacks of coastal protection hard engineering include disruption of natural processes, high costs and maintenance, visual impact, potential habitat loss, and long-term sustainability concerns.

References

“Coastal Engineering: Processes, Theory and Design Practice” by J.A.C. Walkden
“Coastal Engineering: An Introduction” by J.W. van der Meer
“Coastal Engineering: Concepts, Processes, Design” by P.D. Komar and A.J. Raven.
“Shoreline Management Guidelines” by the National Research Council of the National Academies.
“The Performance of Seawalls and the Implications for Coastal Risk Management” by C.K. Shum, D.F.R. Cleary and P.D. Komar
“Seawalls as hazard-mitigation measures: a case study of their impacts on beach and nearshore environments” by R.C. Beavers, J.D.B. Jackson and J.J. Williams.
“Gabions in coastal engineering” by S.K. Kana, W.J. van de Graaff and J.A.C. Walkden
“Groynes in coastal engineering” by S.K. Kana, W.J. van de Graaff and J.A.C. Walkden.