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Unlock This CourseSea walls are one of the most common types of hard engineering used to protect coastlines from erosion and flooding. These massive concrete or stone barriers stand like giant shields between the land and the sea, absorbing the power of crashing waves. As climate change brings more extreme weather and rising sea levels, sea walls have become increasingly important for protecting coastal communities, infrastructure and valuable land.
Key Definitions:
Sea walls work by creating a solid barrier that absorbs and reflects wave energy. When waves hit the wall, their energy is either absorbed by the structure or bounced back out to sea. This prevents waves from reaching the land behind, protecting it from erosion and flooding. The wall must be built high enough to cope with storm surges and strong enough to withstand constant battering from waves.
Not all sea walls are the same. Engineers design different types depending on local conditions, available materials and the level of protection needed.
These are the most traditional type, built as straight vertical barriers. They're effective at reflecting wave energy but can create strong backwash that may cause scouring at their base.
Made from reinforced concrete or large stone blocks. Built with deep foundations to prevent undermining by waves.
Reflects waves directly back to sea, creating turbulent water conditions in front of the wall.
Suitable for areas with limited space where maximum protection is needed in a small area.
These walls have a curved face that deflects wave energy upwards and back out to sea. This design reduces the force of waves hitting the wall and minimises dangerous spray.
Built with a series of steps or terraces, these walls break up wave energy more gradually. Each step absorbs some energy, reducing the overall impact on the structure.
The world's longest sea wall is in South Korea - the Saemangeum Seawall stretches for 33.9 kilometres! It was built to reclaim land from the sea and protect against flooding.
Sea walls offer several important benefits that make them popular choices for coastal protection:
Sea walls provide very effective protection against both erosion and flooding. They can withstand powerful storm waves and protect valuable land and property behind them. Unlike soft engineering solutions, they offer immediate and reliable protection.
Well-built sea walls can last 50-100 years with proper maintenance. This makes them cost-effective over time, despite high initial construction costs. Many Victorian sea walls built in the 1800s are still protecting coastlines today.
Despite their effectiveness, sea walls also have significant drawbacks that must be considered:
Sea walls are extremely expensive to build and maintain. Construction costs can reach £5,000-£10,000 per metre, making them one of the most expensive coastal defences. Regular maintenance is also costly as salt water and constant wave action cause ongoing damage.
Sea walls can have serious environmental consequences. They often destroy natural habitats like beaches and rock pools. The artificial structure disrupts natural coastal processes and can prevent wildlife from accessing breeding or feeding areas.
Reflected waves can increase erosion of nearby unprotected coastline and make water conditions dangerous for boats and swimmers.
Large concrete walls can be unsightly and block sea views, potentially affecting tourism and property values.
People may develop in areas behind sea walls, increasing risk if the wall fails during extreme events.
In 2014, storms destroyed a section of the sea wall protecting the railway line at Dawlish, cutting off Cornwall and Devon from the rest of the UK's rail network. The wall was rebuilt at a cost of £80 million, demonstrating both the importance and expense of sea wall maintenance. The new wall was designed to be higher and stronger to cope with climate change impacts.
Building an effective sea wall requires careful planning and engineering expertise. Several factors must be considered:
Engineers must study local wave patterns, including the height, frequency and direction of waves. Storm conditions and potential future changes due to climate change must also be considered. The wall must be designed to withstand the most extreme conditions expected.
The foundation is crucial for sea wall stability. It must be deep enough to prevent undermining by waves and strong enough to support the wall's weight. Poor foundations are the main cause of sea wall failure.
Before construction, engineers conduct detailed surveys of the seabed, rock types and existing coastal processes. This information helps determine the best design and construction methods for local conditions.
Sea walls require ongoing maintenance to remain effective. Regular inspections check for cracks, erosion of foundations and damage from storms. Repairs must be carried out quickly to prevent small problems becoming major failures.
London's flood defences include 180 kilometres of sea walls along the Thames. These walls, combined with the Thames Barrier, protect 1.25 million people and £200 billion worth of property from flooding. The walls are constantly maintained and upgraded to cope with rising sea levels. Some sections have been raised three times since original construction, showing how sea walls must adapt to changing conditions.
Modern sea wall design is evolving to address traditional problems. New approaches include:
Modern sea walls increasingly incorporate features to support wildlife, such as artificial rock pools, textured surfaces for marine life and integrated habitat creation. These "living sea walls" provide protection while maintaining some environmental benefits.
New sea walls are designed to be easily modified or raised as sea levels rise. This flexibility helps manage the long-term costs and effectiveness of coastal protection.
Sea walls remain one of the most important tools for protecting coastlines, despite their high costs and environmental impacts. As climate change increases coastal risks, the role of sea walls in protecting communities and infrastructure becomes even more critical. However, successful coastal management increasingly combines sea walls with other approaches, including soft engineering and managed retreat, to create comprehensive and sustainable coastal protection strategies.
Understanding sea walls helps us appreciate both the power of human engineering and the ongoing challenge of living alongside the sea. As future geographers and planners, recognising when sea walls are appropriate - and when alternative approaches might be better - is essential for sustainable coastal management.