Starter: Mind-map all the different things people use coast lines for. What are Coasts used for?
Some coastlines are under threat of erosion causing cliffs to retreat and beach material to be lost. Others are at risk from coastal flooding . In many cases the decision has been made to try and reduce the erosion to protect the coastline. This is called COASTAL MANAGEMENT. Coastal Management = The attempt by people to maintain the natural features of the coast for their own advantage
Types of Coastal Management HARD ENGINEERING Hard engineering options tend to be expensive and short-term . They may also have a high impact on the landscape or environment. SOFT ENGINEERING Soft engineering options are often less expensive than hard engineering options. They are usually also more long-term and sustainable , with less impact on the environment.
GROYNES – Wooden/concrete barriers built at right angles to the beach.
Very commonly used
They help build up beach material by preventing longshore drift.
Groynes are small scale solutions and are cheaper than sea walls.
Groynes reduce sediment loss from LSD, which may have an effect on areas downcoast (as these areas might get starved of material and their beaches get smaller).
They have a short lifespan.
Vertical or sloping walls, built along the shoreline
Usually made of concrete .
They concentrate wave energy and reflect it back at the sea .
Often controversial as they are ugly and can be destroyed eventually.
Waves scour at the bases of the walls & eventually undermine them, causing failure. As a result, seawalls only provide temporary protection before needing replacement.
They are expensive .
The wall receives maximum impact which weakens the structure.
Designed to reduce the energy of the waves
The structures absorb the energy of the waves before they reach the cliffs. This method prevents wave scour.
Allow sediment to pass through them , which means that LSD is not stopped .
They are also very cheap , but they do need to be replaced quite often & can be regarded as ugly.
Large boulders that are lain against the cliff / on the beach like a wall
They are permeable structures so allow water through but they are able to dissipate wave energy by absorbing the impact of the waves.
Boulders are much cheaper than sea walls & are longer lasting .
However, some consider them ugly & can reduce the recreational value of the beach.
They can also act as groynes & can prevent LSD
Rock Armour (Rip-Rap)
Similar to the Rip-rap method of protection (they dissipate wave energy etc).
However, gabions use smaller rocks and are encased in a wire mesh
Potential problems arise when the wire mesh breaks ( risk of injury ) and could also say that they are pretty ugly .
Gabions may not last for a long period of time (5-10 years)
Replacement of sand/pebbles on eroding beaches.
Beaches are the best natural protection against erosion as they dissipate wave energy
The best example is the nourishment of beaches at Miami Beach where 17.7 million m³ of sediment was built up
The problem with beach nourishment is that one severe storm event may remove vast amounts of the expensive sediment.
Short life span
Beach Nourishment / Replenishment
Sand dunes and cliffs are a natural sea defence .
They dissipate wave energy and protect the area behind from flooding .
They are stabilised by fences or by planting grasses to hold the sand and rocks together.
This is cheap and effective but easily damaged by people if not maintained and have a short life span
This is where in certain areas, the sea is allowed to reclaim (flood) the land that was once covered by the sea.
This often means that farmland is lost , but the pressure of floods are reduced because it creates salt marshes that can be flooded and can absorb the energy.
A natural and long-term sustainable solution.
Does require compensation for land that is lost.
Sea Wall Do nothing – managed retreat Beach Renourishment Groynes Cliff reshaping Beach Renourishment Rock Armour
Method How does it work? Advantages Disadvantages Groynes Sea Wall Revetments Rock Armour Gabions Beach renourishment Beach reshaping Managed Retreat
Working in groups of 3
Look through the booklet of activities
Timeline for the day ( important = meet in North carpark @ 0745, return @ 1700)