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 Types of Coastal Coastal

ManagementManagement

HARD HARD ENGINEERINGENGINEERING

Hard engineering Hard engineering options tend to be options tend to be expensiveexpensive and and short-termshort-term. .

They may also They may also have a high impact have a high impact on the landscape on the landscape or environment. or environment.

SOFT SOFT ENGINEERINGENGINEERING

Soft engineering Soft engineering options are often options are often less expensive less expensive than than hard engineering hard engineering options. options.

They are usually They are usually also also more long-more long-term and term and sustainablesustainable, with , with less impact on the less impact on the environment. environment.

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.

GROYNES – Wooden/concrete barriers built at right angles to the beach.

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.

SEA WALLSSEA WALLS

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.

REVETMENTSREVETMENTS

• 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)

GABIONSGABIONS

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 / ReplenishmentBeach Nourishment / Replenishment

Beach reshaping.•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

MANAGED RETREATMANAGED RETREAT•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 reshapingBeach

Renourishment

Rock Armour

Method How does it work? Advantages Disadvantages

Groynes

Sea Wall

Revetments

Rock Armour

Gabions

Beach renourishment

Beach reshaping

Managed Retreat

Dorset tripDorset trip

• Working in groups of 3

• Look through the booklet of activities

• Timeline for the day (important = meet in North carpark @ 0745, return @ 1700)

• What to bring?