At £5,000 each, groynes are relatively cheap and, if well maintained, can last up to 40 years. A larger beach, with more space for activities, attracts more tourists, which boosts the local economy.

Rock groynes at Sandbanks, Poole, have concrete crests for people to walk along to reach a viewing or fishing point. Groynes also act as windbreaks

At £110 a metre, they are relatively cheap and easy to construct. Gabions are often constructed on site using local pebbles. This makes them much cheaper than sea walls, rock armour or groynes. It also makes them ideal as a quick-fix solution. For the cost, they are good value for money, as they may last 20-25 years.

They blend in better than other hard engineering methods, especially when sand is blown into them or when they are covered by vegetation.

Groynes are barriers, which impede walking along a beach. They are also dangerous, as they have deep water on one side and shallow water on the other. This is a particular hazard to children who find it hard to resist climbing on them

By trapping sediment, groynes restrict the supply of sediment down-drift. For example, the new groynes at Poole restrict sediment movement towards Bournemouth. The problem is merely passed on to incur more cost.

Groynes may be considered unattractive, especially degraded ones.

Rock armour makes access to the beach difficult, as people have to clamber over it or make long detours. People may have accidents when clambering over it as rocks may be unstable and, if rocks are regularly covered by the tide, they may collect slippery seaweed, which accentuates the hazard

Rock armour is ugly and it often covers vast areas of a beach. Driftwood and litter become trapped in the structure and imported rocks do not blend in with the local geology.

Highly resistant rocks from Norway and Sweden are often used in preference to rocks from local quarries. This may cause resentment and it inflates the cost considerably.