(Engineering) Coastal Defences Flashcards
Sea wall
Coastal defence Concrete -disadvantages: Expensive to maintain Reflects wave energy Ugly -advantages: Works with natural processes Protects land behind
Groynes
Timber/rock structure built angled to coast
Traps sediment (LSD), builds up the beach
-disadvantages:
Unnatural and ugly
Beaches further along suffer due to loss of sediment deposition.
-advantages:
Effective prevention of erosion
Creates walks (promenade)
Gabions
Large stacked boulders Disadvantages: Intrusive Dangerous Low habitat value Difficult to install Advantages: Absorbs wave energy Allows beach build up Durable (long lasting)
Revetments
Sloping wooden/concrete/rock at foot of cliff Breaks wave energy (prevents erosion) Disadvantages: Intrusive/ugly Needs high levels of maintenance Advantages Not expensive to build
Barrages
Partially submerged structures Controls tidal flow of sea Disadvantages: Expensive Alters habitat Intrusive Prevents boat access Advantages: Environmentally friendly? Durable
Offshore reefs
Rock barrier (partially submerged) Breaks up wave energy (ARTIFICIALLY) Disadvantages: Visually unappealing Potential navigation hazard Advantages: Effective permeable barrier.
Beach nourishment
Additional sand or pebbles (increase height or width)
Sediment usually dredged from nearby seabed
Advantages:
Cheap
Looks natural
Increases tourist potential
Disadvantages:
Needs constant maintenance (due to erosion and LSD)
Dune stabilisation/regeneration
Marram grass planted to increase/stabilise sand dune population Areas fenced off (protection) Advantages: Maintaining natural coastal environment Provides habitats Cheap Durable/sustainable Disadvantages: Time consuming (hand planted) Negative responses (due to fenced off areas)
Managed retreat
Areas of coats are allowed to erode
Advantages:
Retains natural balance of coastal system
Eroded material encourages development of beaches and salt marshes
Disadvantages:
People lose their livelihood (eg. Farmers losing land etc.)
Land-use management (coastal zone)
ICZM
E.g. beach nourishment/dune regeneration/coastal defences. Advantages: Natural (provides habitats) Cheap Attracts tourists Disadvantages: Time consuming Constant maintenance Sand from somewhere else
Do nothing
Allowing natural forces to manage themselves -continued erosion and LSD Advantages: Flooding=deposited material/fertilises farmland Cheap Environmentally friendly Disadvantages: Destroys homes/land Erosion Flooding
Hold the line
Maintain current defence or build new ones to ensure coastline stays where it is.
Advance the line
Build new defences seaward of existing line,
