Managing UK & Global Coastlines

Why Coastlines Need Managing

Around the UK, roughly 17 million people live within 5 km of the coast. Storms, rising sea levels and the erosion of soft cliffs put homes, farmland, businesses and ecosystems at risk. Coastal managers have to balance the cost of protecting the coast against the value of what is being lost — and they have to do this with the climate changing faster than the cliffs themselves. Cost-benefit analysis is at the heart of every decision: spend a million pounds to save a road, or accept that the road will fall into the sea?

Key Fact

Coastal management uses two main approaches — hard engineering (working against the sea) and soft engineering (working with natural processes). Most modern Shoreline Management Plans combine both.

Hard Engineering Strategies

Hard engineering uses solid, engineered structures to absorb or block wave energy. The four main strategies are sea walls, rock armour (rip-rap), groynes and gabions. A sea wall reflects waves back out to sea and protects the land behind it; a typical concrete sea wall costs around £5,000 per metre but has a lifespan of fifty years or more. Rock armour is large boulders dumped at the foot of cliffs to break up wave energy. Groynes are wooden or rock fences built across the beach to trap sediment moving by longshore drift, widening the beach so it absorbs wave energy before it reaches the cliff. Gabions are wire cages of stones used as a cheaper, shorter-life option in lower-risk locations.

Hard engineering works quickly and gives communities visible reassurance, but the structures are expensive, can scar the landscape and may starve neighbouring stretches of coast of sediment. The classic example is Mappleton on the Holderness coast: rock groynes built in the 1990s now protect the village, but the cliffs to the south are eroding faster because longshore drift can no longer replenish their beaches.

Soft Engineering Strategies

Soft engineering works with the natural system instead of against it. Beach nourishment imports sand from offshore to widen a beach so it absorbs more wave energy — the sand at Bournemouth has been topped up several times since 1970. Dune regeneration plants marram grass and uses fences to rebuild sand dunes that act as a natural sea wall. Salt-marsh creation deliberately allows low-value land to flood so that mud, plants and tidal channels can develop — the marsh then absorbs storm surges before they reach the sea wall behind. Soft methods are usually cheaper to maintain and look more natural, but they need topping up and may not protect against extreme storms.

Hard engineering is high-cost, high-impact and gives a quick result — useful where the value of property is very high (a town centre, a port, a nuclear power station). Soft engineering is lower-cost in the long term and protects ecosystems, but is best suited to lower-value coastlines where there is space for the system to flex. The trick is choosing the right tool for the right place: a sea wall in front of Blackpool Tower makes sense; a sea wall in front of an empty saltmarsh does not.

Hold the Line vs Managed Retreat

Decision-makers do not just choose between hard and soft methods — they also choose how much of the coast to defend at all. The four classic Shoreline Management Plan options are hold the line, advance the line, no active intervention and managed realignment. Managed retreat — sometimes called managed realignment — is increasingly used on the East coast of England, where defending soft, low-lying land is no longer cost-effective. At Medmerry in West Sussex (2013), the Environment Agency breached an existing sea wall and let 183 hectares of farmland flood. A new defence was built 2 km inland, and the flooded zone became a salt marsh that absorbs storm surges and protects 348 properties in the village behind.

The North Norfolk coast is one of the fastest-eroding shorelines in Europe. At Happisburgh, the cliffs have retreated by more than 250 m since 1600, and homes have fallen into the sea since 1990. The Shoreline Management Plan recommends ‘no active intervention’ here: the cost of defending such a low-population area outweighs the cost of buying out residents. Compare this with Cromer further along the coast, where a sea wall, groynes and beach nourishment hold the line because the town’s tourism economy is worth defending. The same coastline gets two opposite policies based on cost-benefit reasoning.

Integrated Coastal Zone Management

Modern coasts are not managed metre by metre — they are managed as whole stretches of shoreline. Integrated Coastal Zone Management (ICZM) brings together councils, the Environment Agency, conservation groups and local people to make co-ordinated decisions for a sediment cell — the natural stretch of coast within which sand and shingle move. Shoreline Management Plans cover the coast of England in about twenty separate plans, each built around a sediment cell, and set a policy for every stretch in 0–20, 20–50 and 50–100 year time horizons. This stops one council building a sea wall that wrecks the beach next door.

Small Island States & Sea Level Rise

For some countries the question is not how to defend the coast but whether the country itself will survive. The Maldives sits an average of 1.5 m above sea level, and the IPCC projects 0.4–0.8 m of global sea level rise by 2100. The government has already built a 3 m sea wall around the capital Malé (paid for largely by Japanese aid) and is constructing the artificial island of Hulhumalé at 2 m above sea level. The Republic of Kiribati has bought 20 km² of land in Fiji as future relocation insurance. These responses cost hundreds of millions of dollars in countries that did not cause climate change, raising sharp questions about climate justice and the future status of environmental refugees.