Coastal management techniques are introduced in a coastal environment because of the increasing need to protect and manage coastal landforms, landscapes and surrounding areas. There are two main aims of introducing coastal management in an area:
- Providing defence against and mitigating (reducing) the impacts of flooding
- Providing protection against and mitigating the impacts of coastal erosion
Certain types of management can target specific aspects of a coastline, and introduce some other aims of managing coastlines:
- Stabilising beaches affected by longshore drift
- Stabilising sand dune areas
- Protecting fragile estuarine landscapes
There are two main forms that coastal management can take, hard engineering and soft engineering.
Hard engineering is when a physical change is made to a coastal landscape using resistant materials, like concrete, boulders, wood and metal. Hard engineering encompasses the idea of working against nature, because the approaches are quite unnatural, involving construction. Hard engineering techniques tend to be quite expensive and be on a large scale. There are various types of hard engineering techniques, as follows:
|Name of technique
|How it works
|Sea wall (recurved)
|The wall is at the back of the beach, against the cliff face or other such feature lying behind the beach. As a wave moves up the beach, it eventually reaches the wall, the curve causes the wave to be thrown back, which then interrupts the path of the next incoming wave. This means that wave energy is significantly reduced, so much less damage is done to the landscapes.
A sea wall also acts as a flood barrier.
|This is an effective way of reducing wave energy before waves hit the landforms and area behind the beach, so they are protected and less damage is done.
|Sea walls often look very unattractive in a coastal area, as they do not really blend in to the natural surroundings. This may mean that as the area is physically less appealing, there are less visitors so less income to an area, so having economic impacts as well as environmental. Another economic disadvantage is that sea walls cost quite a lot to build and repair. To build, a sea wall may cost between £3000 and £4000 per metre, and depending on the damage, it can be up to around £5000 per metre to repair it.
|Rock armour/Armoured blocks/Rip-rap
|Rock armour is essentially just large rock boulders which are placed in front of the cliff or sea wall. As waves come up the beach, they reach the boulders before the cliffs or wall, so the rocks take the force of the waves, dissipating the energy before the waves can hit behind the boulders.
|This is a good technique because it is in general, very effective at absorbing the energy of the waves, and dissipating it before the waves can attack the cliffs/sea wall. It also builds up the beach further. They can provide a facility which will attract different types of people, for example, on some beaches with rock armour, people go to fish from the boulders, providing business for local industries.
|This is quite an expensive technique, because depending on where the boulders come from, it can cost a lot to transport them to the beach. In addition, the boulders do not look particularly attractive on the beach, so in some cases can deter people from visiting the beach.
|These are structures, usually rock or wood, which extend out into the sea from the back of the beach perpendicular to the water. The idea is that as longshore drift occurs, they interrupt this process by blocking sediment from moving further downdrift. This allows the beach to build up more in certain areas
|They are effective at causing the beach to build up more, so then preventing further erosion of the coastline, as a more built up beach is a natural barrier to erosion.
|Although they cause the beach the build up in some areas, by stopping the natural movement of sediment along the beach, it starves the beach further down of sediment, meaning more erosion will take place in these areas. They are quite an unattractive and very unnatural form of coastal management, so make the beach less appealing. They are also very expensive to build and maintain.
|These are concrete/wooden structures which are designed to break to wave and absorb the energy. They are placed along a beach and prevent erosion as they weaken the energy of the waves against the coastline behind the structures.
|They are an effective way to reduce to wave energy before water hits cliffs. Once they are built, costs of maintenance are not too high.
|Building costs of revetments can be very high, so economically, they may not be the most viable technique. They are also very unnatural and unappealing to the eye at the coast, so make the beach less attractive.
|These are structures whereby small rocks are contained within a steel mesh cage, and a joined set of these cages are placed at the back of the beach. The idea is that as waves come in, the energy is dissipated by the gaps between the rocks in the cages, so there is less energy to attack the cliff.
|In general, gabions are a very cheap method of coastal management.
|They are not hugely effective due to using only small rocks, which are limited in capability to dissipate wave energy. They are also quite a short-term resolution, lasting between 5 and 10 years usually, before needing replacing, so over time, costs can accumulate. They do not look particularly natural or attractive on the beach.
|This involves securing the cliffs by putting iron bars into the cliff face. Not only do the bars make the cliff more stable, but they also help to absorb some wave energy, meaning less damage to the cliffs themselves.
|Stabilising the cliff means the prevention of landslides and other mass movement, as the foundations of the cliff are more securely connected. It also gives a relatively natural appearance, as usually the bars are hidden within the cliff.
|Although the cliff is secured to some extent, this does not provide a direct barrier between the cliff and the waves, so it is still very much open and susceptible to erosion by the waves, so its effectiveness is limited.
|These are constituted of concrete or natural blocks which are sunk offshore to change the direction of the wave. They force the waves to break before reaching the shore, so significantly reducing their energy prior to them reaching the coast.
|It means waves have less energy to erode the beach, allowing a greater build up of the beach, which, in turn, will prevent further erosion. As the blocks are in the sea, they are hidden from view to some extent, so the beach remains having a natural, attractive appearance.
|In strong storms, they can be susceptible to movement and weakening, so their impact is limited. They are also quite difficult to install, so it can be a time-consuming and expensive process.
|These act as a dam across an estuary, preventing flooding by controlling the water.
|They are effective ways to stop flooding in these areas, so reducing risks of erosion. They can also help to create fresh water lakes which can be habitats for a great range of wildlife.
|They are very expensive to build and maintain. Many environmentalists oppose the construction of barrages, because it causes a permanent rise in water levels, which can be damaging to many structures and areas around the barrage.
Soft engineering involves using natural systems for coastal defence, like beaches, dunes and salt marshes, which can absorb and adjust to wave and tide energy. Generally, it means working with nature, so allows the erosional processes to occur but uses methods to limit its damage. The systems are manipulated but are not drastically changed. Soft engineering techniques are as follows:
|Name of technique
|How it works
|This is when sediment is added to the beach in order to replenish it after some has been lost due to longshore drift. Often, it involves moving material from one end of the beach to the other.
|It creates wider beaches, so waves lose their energy more quickly before reaching the cliffs, meaning they have less erosional power. It has a very natural appearance and does not involve any artificial addition to the coast, so the area remains appealing to people.
|The process can harm wildlife in both the places sediment is being added to and where it is being removed from. It can be quite an expensive process because it needs to be repeated many times, and also, in some cases the sediment is sourced from a different beach, so transport costs can be high.
|This can include strategies like replanting areas with marram grass to stabilise the surface, afforestation, selective grazing, restricting access for people, creating boardwalks for tourists to use, and providing information to visitors about how the area can be damaged.
|It makes the sand dunes a lot more stable, so they are less susceptible to erosion. Most techniques involved in this are quite cheap, so it is economically viable. It means the beach remains to have a natural appearance.
|Many of the processes need repeating, like planting marram grass, so it is quite time-consuming and can eventually be relatively costly. There is also no guarantee that tourists will stick to the provided paths, so its effectiveness may be limited.
|This technique means breaching the current sea defences so that the water reaches land behind, but making use of this in some way, like turning it into a salt marsh.
|Creating a landscape like a saltmarsh behind the beach means that more wildlife is facilitated. It could also be economically beneficial for an area, as money no longer needs to be spent on creating hard sea defences, and there is more tourism from people visiting the marshes.
|There is often conflict with landowners who will be losing land as a result of this, for example, farmers are often at risk of their land being destroyed by the sea after the defences are breached.
|This means analysing the way in which the land surrounding the coast is used and how people behave around it. It also means providing education to people about how the area can be protected and conserved. Authorities can plan for the future and how to protect the coastline.
|This strategy allows areas to be ahead of the threats to the coastline – by doing land-use management, it secures the land before there is serious threat from erosion, so can be quite effective in advance. Depending on the approaches taken, this technique is not too expensive.
|When authorities have to make decisions about how the land is used, it may mean that other areas have to be located to put certain facilities in, rather than in close proximity to the coastline, which can be quite difficult. It could also affect the tourism industry at the coast if land use is limited.
|There is ongoing debate about whether coastal protection is actually a necessary priority for funds. Doing nothing about it means that money can be put into improving things/areas with high economic value for lots of people.
|It is a good idea for the economy to do nothing about coastal protection, as often, management techniques are very expensive, but not actually massively effective in the case of storms, when erosional force against the coast is very strong.
|Although in the short term doing nothing can be economically beneficial, long term, it may eventually mean that lots of money has to be spent on repairs after damage is done through erosional processes.