Types of coastal protection

Types of coastal protection

1) A groyne is a fence-like rigid structure from an ocean floor, or bank of a river. They are perpendicular to the coast and interrupt water flow, and they limit the amount of sediment. Groynes are designed to slow down longshore drift and build up the beach. They are often made of tropical hard woods, or concrete. Groynes may have a life of 15-20 years but often have to be replaced rather than repaired.

2) A gabion cage is a metal cage filled with rocks, and they are stacked to form a simple wall. They are used to protect a cliff or area in the short term only, since they are easily damaged by powerful storm waves and the cages tend to rust quite quickly. Gabion cages have the advantage of ease of use and are quite cheap, but their life span is short.

Gabion cages acting as barriers to incoming waves.

Build up of sediment and the beach.

3) Revetments are sloping structures placed on banks or cliffs in such a way, to absorb then energy of incoming water. They are mainly made of stone or wood. Stone revetments are also the most economical and quickest to install of all of the methods of erosion control, and are very effective. They are very easy to maintain. This is a form of hard engineering.

4) Sea walls are usually massive, vertical structures which are used to protect areas from heavy wave action. The most common materials they are made out of are, poured concrete, concrete blocks, and metal sheet piles. Sea walls are curved and are designed to deflect incoming wave energy, therefore reducing the effects of strong waves. They are very expensive to build, and poor designed sea walls will require constant maintenance repairs to be carried out.

A steep stoned revetment.

The wave energy is absorbed when it crashes into the stone revetment.

A curved sea wall which will deflect incoming waves.

5) Beach replenishment or beach nourishment is a non-structural method which involves the transport of the nourishment material from one area to the affected area. It is very expensive to carry out this, and if it is a poorly designed project, then there could be a severely impacted ecosystem. Once a beach is nourished, it almost always is necessary to regularly renourish it since nourished beaches tend to erode faster than natural beaches.

6) Rip Rap or Rock armour is normally made from hard rock, especially granite, or concrete rubble. It normally works by absorbing the impact of a wave before the wave reaches the cliff or sea defense, and so minimizes the erosion caused by the wave.

I. Groynes- Hard engineeringII. Gabion cages- Hard engineeringIII. Revetments- Hard engineeringIV. Seawalls – Hard engineeringV. Beach replenishment- Soft engineeringVI. Rip-rap – Hard engineering

The differences between hard and soft engineering are, that hard engineering costs more to build then soft engineering, and requires a lot of man power to build. Mostly Hard engineering does not fit in with the natural environment of the place, while soft engineering mostly does. Soft engineering has a natural feeling, while hard engineering has a more industrial feel to it.