Coasts- Coastal Management Flashcards
Reasons for coastal management
- coastal erosion
- coastal flooding
- failure of former defences
Why are coastal defences becoming increasingly more important?
- global warming- sea level rise
- high sea levels increase risk of flooding
- increasing population- more people living there increases value of land
- failure of past defences- some areas now starved of sediment and more exposed to erosion
Definition of ‘hold the line’
Maintain current defences or build new ones to ensure the coastline stays where it is
Definition of ‘advance the line’
Build new defences seaward if existing line
Definition of ‘retreat the line’ (managed retreat)
Allow the coastline to retreat due to flooding and erosion but closely manage the rate and location of this retreat
Define ‘do nothing’ as a management strategy
Low value areas of land left to natural coastal processes as not deemed valuable enough to spend money on defences
Social factors which may dictate the chosen management strategy
- number of people directly impacted
- history/culture
- employment
Economic factors which may dictate the chosen management strategy
- value of infrastructure and housing
- value of businesses
- cost of the defences
Environmental factors which may dictate the chosen management strategy
- value of ecosystem
- how common the ecosystem is
- pollution to ecosystem
Political factors which may dictate the chosen management strategy
- who will fund the project eg. local council
- voter opinion/importance
- relationship with other areas
What is a Cost Benefit Analysis?
- 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
- a project where cost exceeds benefit is unlikely to be given permission to go ahead
What are ‘tangible’ costs and benefits?
Where costs and benefits are known and can be given a monetary value
What are ‘intangible’ costs and benefits?
Where costs may be difficult to assess but are important (eg. visual impact)
What is beach nourishment?
The addition of sand/pebbles to an existing beach to make it higher or wider
The sediment is usually dredged from the nearby seabed
Advantages and disadvantages of beach nourishment
ADVANTAGES-
-relatively cheap and easy to maintain
-looks natural and blends in with existing beach
-increases tourist potential by creating a bigger beach
DISADVANTAGES-
-needs constant maintenance because of the natural processes of erosion and longshore drift
What is dune regeneration?
Marram grass can be planted to stabilise dunes.
Areas can be fenced to keep people off newly planted dunes
Advantages and disadvantages of dune regeneration
ADVANTAGES- -maintains natural coastal environment -provides important wildlife habitats -relatively cheap and sustainable DISADVANTAGES- -time consuming to plant marram grass -people may respond negatively to being kept off certain areas
What is managed retreat?
Allowing the coastline to retreat in a managed way eg. creating salt marsh environments by deliberately breaching flood banks that protect low lying farmland
Advantages of managed retreat
- sand dunes act as a good barrier against coastal flooding and erosion
- can be exploited as a natural defence against the sea
- creating salt marshes increases biodiversity
Advantages and disadvantages of doing nothing to prevent further erosion
ADVANTAGES-
-saves money if the land is worth less than the defence would cost
DISADVANTAGES-
-eventually the cliffs may be eroded so far that high value land becomes at risk- so sea defences will have to be constructed eventually
What are sea walls?
Stone or concrete walls at the foot of a cliff or top of a beach
Usually have a curved face to reflect waves back into the sea
Advantages and disadvantages of sea walls
ADVANTAGES-
-effective prevention of erosion
-often have promenade for people to walk along
DISADVANTAGES-
-reflect wave energy rather than absorbing it
-can be intrusive and unnatural looking
-very expensive to build and maintain
What are groynes?
Timber/rock structures built at right angles to the coast
Trap sediment being moved along the coast by longshore drift-building up the beach
Advantages and disadvantages of groynes
ADVANTAGES-
-work with natural processes to build up beach- increases tourist potential
-relatively inexpensive
DISADVANTAGES-
-starve beaches further along the coast of sediment
-unnatural and can be unattractive
What are gabions?
Consist of metal cages containing rock.
Usually constructed at the base of a cliff to absorb wave energy and reduce erosion
Advantages and disadvantages of gabions
ADVANTAGES- -relatively cheap to construct DISADVANTAGES- -not very attractive -not particularly effective (compared to for instance sea walls)
What are revetments?
Sloping wooden, concrete or rock structures places at the foot of a cliff or the top of a beach.
They break up the waves energy
Advantages and disadvantages of revetments
ADVANTAGES- -relatively inexpensive to build DISADVANTAGES- -intrusive and unnatural looking -need high levels of maintenance
What are barrages?
- sometimes constructed in bays and estuaries
- partially submerged structures that contain gates that control the tidal flows of the sea and river water from the land
- help provide a more consistent water level
Advantages and disadvantages of barrages
ADVANTAGES-
-can also be used to generate hydro-electricity
DISADVANTAGES-
-have an impact on the environment (obstructs flow of sewage)
-takes a long time to construct
-very expensive to construct
Advantages and disadvantages of offshore reefs
ADVANTAGES-
-provides a new habitat
-less intrusive and less of an impact on LSD
-breakwaters create favourable waves for surfers
-creates extra beach
-improves biodiversity
DISADVANTAGES-
-causes side deposits of mud and seaweed
-captures litter from ships
-currents around the edge of breakwaters dangerous for swimmers
Shoreline management plans (SMP) aims
- assess risk associated with coastal erosion
- address risk in sustainable way
- ensure management plans comply with nature conservation
- provide policy for coastal management
- assess risks to developed and natural environment
- documents constantly renewed
- promote long term management policies into 22nd century
What coastal management is in place at Slapton Sands
- beach at Torcross artificially strengthened by sea wall and rock armour installed
- Slapton Ley designated sight of special scientific interest (SSSI)
- barrier beach at Slapton has A379 running along it- which requires protection to ensure local people can travel
What challenges have coastal managers faced in Slapton?
- in 2001 a large storm destroyed 250m of road across barrier beach
- a grant of £245,000 was all managers had to fix it
- 2014 storm destroyed many defences in Torcross, Hallsands and Beesands- £95,000 received as part of gov. Emergency Flood Recovery Fund
- however Hallsands is an area of no intervention so funding could not be spent repairing there- residents raised £20,000
What factors does the Shoreline Management Plan for South Devon and Dorset Coastal Authorities consider?
- no. of households at risk
- impact on agricultural land and farming communities
- impact in the environment and wildlife
- whether erosion affects local community infrastructure and transport
Location of Odisha (coastal risk vs reward)
- state on east coast of India
- borders the Bay of Bengal
- India’s 9th largest state by area and 11th by pop.
- coastline features Chilika Lake and Mahanadi Delta
Unique ecology of Odisha
- Chilika Lake is a salty lagoon renowned for bird life
- has 1435km2 of Mangrove forest
- lake acts as temporary store in water cycle and beach is an important store in whole coastal system
Opportunities of living in Odisha
- huge potential for offshore wind, tidal and wave power
- 35% of coastline contains minerals and heavy metal deposits- economic potentials
- opportunities for offshore oil and gas
- many local people employed in coastal fishing- coastal ports provide a source of income
- cultural sites draw in visitors from around the world (leads to growth of tourism industry- income for locals)
Risks of living in Odisha
- coastal communities vulnerable to storm surges and tsunamis
- only 14% of coastline is classes as stable- long term development is therefore risky
- it is hard to predict whether existing defences will have a negative effect more than positive
