Lesson 13-How are coasts managed? Flashcards
What is coastalisation?
-The process where a coast is being developed and people are moving to the coast, increasing the number of people at risk from the marine related environmental activity
-by-product of urbanisation in which people move to cities as majority of large cities are coastal
Why might the risks from a storm surge be exacerbated?
-Removing Natural vegetation like Mangrove forests provide protection against extreme weather events but many are destroyed to make way for toursim services and housing
-Global Warming as the surface of oceans get warmer, it is predicted that the frequency and intensity of storms will increase
Impacts of sea level rise on coastal communities?
-house prices
-insurance companies
-environment damage
-destroyed depositional landforms
-loss of life, culture and homes
Impacts of sea level rise on coastal communities-House Prices
- Causing significantly reduced house pricing and land prices (as the area becomes known to be at significant risk) leading to economic loss for homeowners and local coastal economies
Impacts of sea level rise on coastal communities-Insurance companies
- In the UK, many insureers dont provide home insurance to people living coastlines that are at extreme risk of erosion or storm surges
Impacts of sea level rise on local communities-Environment damage
- Storm surges also damage the environment by destroying plant successions and damaging many coastal landforms.
Impacts of sea level rise on coastal communities-Destroyed deopsitional landforms
- Was seen in 2013, when the spit ‘Spurn Head’ was partially destroyed by a large storm surge. If depositional features are destroyed then erosion may occur more quickly closer to the cliff face, which can increase the risk of collapse of cliffs and threats to land owners.
Impacts of sea level rise on coastal communities-Loss of life, culture and homes
- Forced to migrate to avoid the rising sea levels and the rising risk of flooding. In low-lying countries such as Bangladesh where the coastline is made up of clay sands many people may be displaced due to the potential impacts of climate change on the coast.
Why do we want to manage the coastline?
- To defend human structures as theres potential for new economic loss to occur
How can we manage the coastline?
- Hard engineering- Sea/Rock walls
- Soft engineering- Dune regeneration
What are our options for managing the coastline?
- Hold the line- maintaining the position of the coastline using mostly hard engineering methods
- Advance the line-extending the coastline out to sea by building up the beach and land reclamation
- Do nothing-let nature take its course, this means that along these stretches there are few if any risks of erosion
- Managed realignment/ retreat-low-lying areas are recognised as being threatened by flooding are flooded in a controlled way deliberately
How do we decide which option to use to manage the coastline?
- A cost benefit analysis is carried out before a coastal management project is given the go ahead.
- Costs are forecast and then compared with the expected benefits.
How is a cost benefit analysis calculated?
- Costs are forecast based on known tangible costs of coastal defences such as how much 100m of sea wall will cost to build and maintain, and intangible costs such as the visual impact of the sea wall
- The costs are then weighed up against the benefits for the environment and population
Hard engineering strategies
- Groynes
- Sea walls
- Rip rap/Rock armour
- Revetments
- Offshore Breakwater
Hard engineering strategies-Groynes
- Built perpandoicular to the shore to trap sediment so the beach builds up to absorb wave energy
-Sediment starvation further down beach, Unattractive,Needs maintanence
+Not as expensive,Improves tourist potential with built up beach
Hard engineering strategies-Sea walls
- Walls with a curved surface that absorb and reflect wave energy
- £6000 per metre, ugly and intrusive to landscape
+Highly effective,Tourism benefits as walk ways are created
Hard engineering strategies- Riprap/Rock Armour
- Large concrete or granite boulders at the foot of the cliff. The spoaces between the boulders caused waves to bounce between many surfaces, reducing the energy of the wave
-Dangerous when people are on them,Rocks from elsewhere are intrusive to local geology
+Cheaper than sea walls, Used for recreation like fishing
Hard engineering strategies-Revetments
- A sloped or ramp-like structure that greaks up wave energy
-Need lots of maintenance,Unnatural looking,Slopes are dangerous
+Cost-effective compared to other hard engineering strategies
Hard engineering strategies-Offshore Breakwater
- Rock barrier a little out to sea from the shoreline. This breaks the waves and dissipates their energy before they reach the coast
-Can create navigation barrieer in harbour areas
+Effective, Away from the beach so does not disrupt tourism potential
Soft engineering-Managed retreat
- It involves abandoning existing coastal defences and allowing the sea to flood inland until it reaches higher land or a new line of coast defence.
- Allowing low-lying coastal areas to flood and develop into salt marshes produces a good natural defence against storms.
- It also increases the amount of salt marsh – a threatened ecosystem. It is a relatively cheap method of coastal defence.
- The main cost is one of compensating people for the loss of ‘drowned’ homes and livelihoods.
MAIN RESPONSE TO CLIMATE CHANGE RISING SEA LEVELS
Soft engineering strategies
- Beach nourishment
- Cliff Regrading and Drainage
- Dune rehabilitation
- Marsh Creation
Soft engineering strategies-Beach nourishment
- Adding sand or shingle to a beach to widen it as it creates more surface area to absorb wave energy
-Material subject to erosion and longshore drift so requires maintenance, Dredging the seabed can have bad consequences
+Looks very natural, Bigger beaches are better for tourism, Relatively cheap
Soft engineering strategies-Cliff Regrading and Drainage
- Reducing the angle of the cliff to stablise the slope. Drainage of water also stabilises the cliff against mass movement
-Can look unatural as cliff is flatter, creates cliff retreat, causes dried out cliffs which collapse
+Cost effective
Soft engineering strategies-Dune stabilisation
- Planting species like Marram grass so that the roots bind the dunes. The dunes absorb wave energy and protect the land behind them.
-People walk on dunes and damage them, planting is time-consuming and takes time for it to grow
+Cheap and sustainable, creates habitants for wildlife, maintains a natural environment
