There are several types of coastal protection measures that can be used to reduce erosion. Hard engineering options like groynes, gabion cages, revetments, seawalls, and rip rap absorb wave energy through rigid structures. Groynes interrupt water flow perpendicular to the coast to limit sediment loss. Gabion cages are stacked rock-filled wire cages that act as temporary barriers. Revetments are sloped stone or wood structures that absorb wave energy. Seawalls are massive vertical walls that deflect waves. Rip rap is rock or concrete rubble that minimizes erosion. Beach replenishment involves adding new sediment and is considered soft engineering since it has a more natural appearance and fits better within the environment.

1. 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.

2. 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.

3. 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 engineering
II. Gabion cages- Hard engineering
III. Revetments- Hard engineering
IV. Seawalls – Hard engineering
V. Beach replenishment- Soft engineering
VI. Rip-rap – Hard engineering

4. 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.