Coastal Management: Soft Engineering

Soft Engineering Methods

Beach nourishment involves adding sand or shingle to an existing beach to make it higher and wider. This helps absorb wave energy, reducing erosion and flooding. The new material is often dredged from the seabed or brought from elsewhere.

Dune regeneration is the process of restoring sand dunes by planting vegetation such as marram grass to stabilise the sand. Fencing off areas to prevent trampling helps dunes recover naturally, acting as a natural barrier against the sea.

Managed retreat means allowing certain low-lying coastal areas to flood naturally by removing existing defences. This creates new habitats like salt marshes which absorb wave energy and reduce erosion further inland.

Marsh creation involves deliberately flooding areas behind the coast to form salt marshes. These marshes act as natural buffers, slowing waves and trapping sediment to protect the coastline.

Soft engineering works with natural processes rather than against them, aiming to create sustainable, long-term coastal protection. It is often preferred because it adapts better to changing conditions such as rising sea levels and has a lower environmental impact compared to hard engineering.

For instance, at Happisburgh in Norfolk, managed retreat has been used to allow natural flooding of farmland, creating salt marshes that reduce wave energy and protect inland areas.

Advantages of Soft Engineering

• Environmentally friendly: Soft engineering methods enhance natural coastal features rather than replacing them with concrete or rock. This supports biodiversity and natural habitats.
• Sustainable: These methods work with natural processes, so they tend to be more sustainable over time as they can adapt to changing conditions like rising sea levels.
• Enhances natural habitats: Techniques like dune regeneration and marsh creation provide homes for wildlife such as birds, insects, and marine life.
• Lower cost than hard engineering: Soft engineering is generally cheaper to install and maintain than expensive sea walls or groynes.

For example, beach nourishment at Bournemouth has helped maintain a wide sandy beach that protects the town and provides a habitat for coastal plants and animals.

Disadvantages of Soft Engineering

• Requires regular maintenance: Beaches need topping up with new sand, and dunes require ongoing care to prevent damage from foot traffic or storms.
• Less effective in severe storms: Soft engineering may not withstand powerful storms or extreme weather events as well as hard defences.
• Can be slow to protect: Some methods, like managed retreat, take time to establish natural barriers such as salt marshes before they effectively reduce erosion.
• Limited lifespan: Without continual management, soft engineering features can degrade or be overwhelmed by rising sea levels.

For example, beach nourishment requires sand to be replaced every few years, which can be costly and disruptive.

Case Studies in the UK

Happisburgh, Norfolk – Managed retreat has been used here since 2010. Coastal defences were removed to allow flooding of farmland, creating salt marshes that absorb wave energy. The local community was involved in decision-making, balancing environmental benefits with loss of farmland. Community involvement helps ensure local needs are met and increases the success of such projects. Over time, this has reduced erosion risk to inland areas, although some farmland was sacrificed.

Bournemouth, Dorset – Beach nourishment has been ongoing to maintain the wide sandy beach that protects the town’s seafront. Sand is dredged offshore and pumped onto the beach regularly. This soft engineering approach supports tourism and protects properties from erosion. The local council works with environmental groups to monitor impacts on wildlife.

Sefton Coast, Merseyside – Dune regeneration projects have planted marram grass and installed fencing to prevent trampling. This has stabilised dunes, reduced erosion, and improved habitats for rare species like the natterjack toad. Community volunteers help maintain the area, showing effective local involvement.

Medmerry Managed Realignment, West Sussex – One of the UK’s largest managed retreat schemes, completed in 2013. Coastal defences were breached to allow controlled flooding of farmland, creating 183 hectares of new salt marsh. This provides natural flood protection for nearby villages and enhances biodiversity. The project was planned with local stakeholders and has proved effective in reducing flood risk.

Learning Example: Calculating Beach Nourishment Volume

Suppose a beach needs to be raised by 2 metres over an area of 500 metres length and 30 metres width to protect against erosion. Calculate the volume of sand needed.

Volume = length × width × height

Volume = $500\,\mathrm{m} \times 30\,\mathrm{m} \times 2\,\mathrm{m} = 30,000\,\mathrm{m^3}$

So, 30,000 cubic metres of sand are required for nourishment.