hard and soft engineering Flashcards
4 types of hard engineering
- sea wall
- gabions
- groynes
- rock armour
what is a sea wall? where are they placed? recurved vs flat more expensive? extra stability?
- provide a barrier between sea and land
- placed at back of beach
- recurved sea wall deflect wave’s energy, reducing its erosive power
- recurved walls and more expensive than flat ones
- steps at bottom of sea wall - for protection, extra stability
what is hard engineering ? (3)
- using artificial structures to protect a coastline
- effective
- unnatural
what are groynes?
where are they placed?
what do they do?
where does sediment go?
- wooden/stone structures
- built at foreshore
- approx. 50 m apart at right angles to the Beach
- trap sediment from LSD
- sediment builds up at up drift of groyne
what is rock armour? placed where? position of rocks? what do they do? why are high boulders used? what happens when water gets through gaps in rock?
- made out of 1000’s huge boulders
- placed at back of beach
- downslope arrangement to deflect sea’s energy and reduce wave’s erosive power
- boulders can’t be moved in storm waves
- when water gets in through rock’s gap, pressure is released and this reduces wave’s energy and erosive power
what are gabions? positioned? what happens when water gets in cages? why might they be placed at front of cliff? covered by what?
- cages filled with pebbles from beach
- back of sandy beach to create a low, wall-like structure
- water enters cages and this absorbs/dissipates wave’s energy, reducing the rate of erosion
- may be placed at front of cliff where covered with vegetation - gives stability to a cliff reducing landslides
benefits of sea walls?
disadvantages of sea walls?
social: gives residents a sense of security
economic: last many years if maintained well
environmental: don’t interfere with LSD
social: restrict people’s access to beach
economic: expensive to build £5000 per metre
environmental: destroyer habitats and looks ugly
benefits of groynes?
disadvantages of groynes?
social: Builds a beach - which encourages tourism.
economic: £5000 each, cheap to build
environmental: They trap sediment being carried by longshore drift, builds up beach
social: barriers which can interfere with people walking across beach
economic: because sediment is trapped at updraft, there’s no sediment at down-drift so beach looks uneven
environmental: unattractive, degraded ones (poor quality)
benefits of rock armour ?
disadvantages of rock amour?
social: Cheaper than a sea wall and easy to maintain.
economic: cheap - £1000-3000 per metre
environmental: Can be used for fishing.
social: makes access to beach difficult, reduce tourism
economic: The rocks are expensive to transport.
environnemental: They look different to the local geology, as the rock has been imported from other areas and dangerous when wet, causes injuries e.g. slips
benefits of gabions?
disadvantages of gabions?
social: -
economic: Cheap - approximately £100 per metre.
environmental: blend in better with environment
social: is damaged, they are dangerous
economic: need to be regularly maintained because they get damaged easily
environmental: damaged baboons causes birds feet to get stuck
what is soft engineering? (3)
- works with nature
- less effective
- cheaper
what is beach nourishment? (3)
- replacement of lost sediment
- nourished beach means less waves van get onto beach
- more sediment means wave’s energy is dissipated and absorbs by sand / sediment
what is beach recharge ? (2)
- sediment is taken from bay and placed back onto beach
- takes place every 10 years at Sandbanks in Poole
what is beach recycling? (2)
- the removal of sand from a drown drift area
- and placed on beach where its losing sand (up drift area)
what is beach reprofiling? (3)
- re-shaping of the beach using already existing material
- beach is lowered at destructive waves
- bulldozers move shingle back up to beach
