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Managing coastlines
 Hard engineering
Soft engineering
 
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The coastline is a used environment.  Human beings, plants and animals all use the coastline for different things.  In the case of humans, we use the coastline for agriculture, for fishing, for industry and power generation, for transport routes and for land upon which to live.  However, a lot of these land uses are incompatible with the fact that the coastline is constantly changing. 

 

Erosion processes remove land from some parts of the coastline, whereas deposition processes create new land in other places.  In addition, the fact that the sea level is rising locally and globally could add to these erosion and deposition problems whilst also removing land from use at the coastline.  It is for these reasons that human beings have long sought to control and MANAGE the coastline.  However, there is a huge debate as to how to do this - either by using HARD ENGINEERING or SOFT engineering.


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Hard engineering sea walls, groynes, rock armour

Hard engineering involves the building of entirely ARTIFICIAL structures using various materials such as rock, concrete and steel to reduce or stop the impact of coastal processes.

Sea walls are walls of concrete, supported by Iron pilings dug into the underlying rock, that are designed to prevent coastal erosion. They are generally placed at the foot of vulnerable cliffs or at the top of a beach.  They can be up to 5m high and can be flat faced or curved.  The curved walls are more expensive but dissipate the energy from incoming waves better.  These defences can be up to 6 million per kilometre to construct.  Their good points are that they are very effective, have a reasonably long lifespan and often have walkways along the top for people to walk along.  However, they are very expensive and are accused of being ugly (not aesthetically pleasing!).  Also, sea walls have been known to cause down current scarring, where waves cause more damage to unprotected areas.

Groynes (as seen at Seaton Sluice!) are basically wooded fences that run at right angles to the beach.  These fences run out into the sea, and are designed to interrupt longshore drift and catch sediment as it moves along the coastline, thus widening a beach.   This larger beach can then act as a buffer against waves, as there is more beach to absorb wave energy.  these features can cost as much as 10,000 each, and need to be spaced at 200m intervals.  They are good because they result in a larger beach, which not only protects the coastline but can also be good for tourism.  In addition, they are not that expensive. However, they starve down current (or drift) beaches, which makes them more vulnerable to erosion, and again they are not that attractive.

Groyne at Seaton Sluice

Rock armour - This is a simple strategy that involves the dumping of huge boulders of rock at the base of a cliff.  These rocks help the wave to break an din so doing they absorb the wave energy.  They cost between 1,000 and 4,000 per metre, depending upon the material used, and are relatively cheap and easy to maintain.  They are however unnatural and do not fit with the geology of the cliff line, and can be expensive to transport.  Another type of rock armour are Gabions - which are cages of smaller rocks that work in much the same way.

Rock armour

Hard engineering schemes are effective but expensive, and recent attempts to manage coastal processes have focussed on softer engineering techniques.  These techniques seek to mimic natures own ways of managing coastal processes and to use natural materials and strategies to prevent erosion.  In effect, these measures can be better for the environment, cost less money to implement and maintain, but not totally control the erosion problem. They are a more sustainable way of managing the coastline.
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Soft engineering beach nourishment, dune regeneration and marsh creation.

Beach nourishment is a measure whereby additional sand and shingle is added to a beach to make it higher and wider.  This material is brought onshore by barge, and moved about by large trucks and diggers.  It costs around 3000 per km and is a cheap method.  It will blend in with the beach if the sediment is locally sourced (such as the new sand dune at Seaton Sluice, which was created from dredged sediment for the River Blyth) and will have benefits for tourists.  However, this method needs constant maintenance or else this new sediment will also eventually be eroded by the sea!

Beach nourishment

Dune regeneration basically involves artificially creating new sand dunes along the coastline to act as a buffer between the land and the sea.  Sand dunes occur naturally but are under threat because they are fragile and people walk all over them, ride horses and motorbikes on them and destroy the dune ecosystem.  Using fencing to help trap sand, planting Marram grass into coconut matting (as was done at Seaton Sluice) and encouraging dune formation helps to protect these systems which protect our coastline and absorb storm and wave energy. This can cost 2,000 per 100m and helps to maintain the ecosystem of the area whilst offering protection.  However, it is time consuming to plant the Marram grass and fence off areas, and is less effective than hard engineering schemes. 

 

Managed retreat is a method whereby we humans concede defeat to the power of the sea and allow it to erode and create salt marshes for example.  We can also allow cliff erosion to occur in areas of low value farmland and just compensate farmers for their losses, rather than construct more expensive coastal defences.  This can only work where the coasts of compensation are significantly less than the coasts of building coastal defences, and can be a cheap option.  It can also be beneficial to plants and animals by providing new habitat.  This method is highly controversial however, as land is lost and the human cost can be greater than just financial.  Imagine a farmer told to quit land and a family home that could have been in the family for generations because the council do not want to build a sea defence - the trauma of this is huge. 
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Think abut it

Try the space race below

Watch the video and make a list of pros and cons for each method of controlling coastal erosion