coastal management (2B.11) Flashcards
two types of engineering
- hard engineering: physical management of the coasts to CONTROL/ GO AGAINST natural processes such as erosion and longshore drift
- soft engineering: working WITH natural processes and protections to defend areas of the coastline
different types of hard engineering
- sea walls
made of stone/ concrete and run parallel to the backshore and they usually have curved face to reflect waves back into the sea
- modern walls are able to absorb wave energy and act as physical barrier against erosion
- effective and give people sense of security
- prevent flooding and can be used as a promenade
however,
- they’re expensive (£5000 per linear metre)
- do not fit into natural surroundings
- greatly reduce supply of sediments - gabions
pebbles in wire baskets which when tied can make a wall
- very flexible in terms of placement eg on the backshore or to help hold back mass movement on a cliff
- relatively cheap and easy to maintain
however,
- not suitable for high energy locations- not v strong
- needs frequent repair - rip rap
boulders or specially designed concrete shapes with large s.a to dissapte waves energy
- long lasting and flexible: can be used to protect sea wall base or used as a breakwater/ groyne
however,
- may look unsightly: contrast with natural rock
- access difficulties - revetments
commonly wooden interlocking sloping structures placed parallel to backshore to take force of breaking waves
- absorb wave energy and traps sediments behind them reducing its removal by other erosional processes (builds up beach)
- longshore drift is still able to able to continue and cheaper than sea walls
however,
- made need constant maintenance
- unsightly - groynes
wooden structures built on beach at right angles aimed to slow down longshore drift and trap sediment
- builds up beach so that wave energy is absorbed by the beach rather than on the backshore
- bigger beach increases tourist potential
- not too expensive
however,
- starve beach further down the coast of fresh sediment which often leads to increased erosion elsewhere
- unnatural and obstructs the beach - offshore breakwaters
partly submerged rock barrier in shallow waters designed to break up the waves before they reach the coast
- purpose is to absorb wave energy and dissipate waves before they have chance to damage the foreshore or backshore
- create sheltered water areas- good for water sports/ recreational use
- can protect entrance to harbours (calmer waters)
however,
- expensive £1- £2 million total
- may look unsightly at low tide
- may increase deposition on the landward side reducing longshore drift
different types of soft engineering
- cliff regrading and drainage
- beach nourishment
- dune stabilisation
- managed retreat
sustainable management
is designed to cope with future threats (increased storm events, rising sea levels) for an overall social, economic and environmental benefit but its implementation can lead to local conflicts in many countries.
adopting sustainable coastal management may lead to conflict because:
- coastal natural resources may have to be used to less in order to protect them - so some people lose income
- relocation may be needed where engineering solutions are too costly or not technically feasible
- some erosion and/or flooding will always occur, as engineering schemes cannot protect against all threats.
- future trends, such as sea level rise, may change, creating uncertainty and the need to change plan.
example of conflict caused by sustainable coast management
! not everyone is happy with soft engineering !
EG Happisburgh Case Study (Norfolk coast)
- over 250km of land lost from 1600-1850
- 6- 10m cliffs made of unconsolidated glacial clay
- it would take £15 million to close the gap in sea defeneces and so currently, managed retreat/ do nothing is the likely route: this is also because beaches to the south are supplied by sediment from this area so no hard engineering strategies that could affect the sediment cell are an option
- residents are being geiven time to move out but receieving very little compensation apart from £1000 in moving costs!!
coastal managers argue that H must be seen in a wider context of wider SMP
EG by 2105, between 20 and 35 houses would be ‘saved’ from erosion, with a combined value of £4 million - 7 million
beach regrading and drainagre
a) reduces angle of cliff to help stabilise it (calculated by engineers) b) drains water to reduce pressure therefore preventing/ reducing mass movements
- both natural looking
- both bring confidence to landowners
however,
- regrading effectively causes the cliffs to retreat and is quite expensive: not to mention that engineers may get their calculations wrong/ extreme weather could affect
- drainage is difficult to implement along the whole of cliff without disturbing the cohesion of the rock layers
- drainage doesnt prevent mass movemnt only reduces to some extent
beach nourishment
artificial addition of material to beach to replace sediment lost by erosion, enlarge the each so that it dissipates energy, reduces erosion and increases tourists
- looks natural
- supports local tourist industry
however,
- £20 mill. per km of beach
- sediment must not be sources from elsewhere in the sediment cell
- winter storm conditions mean that it does not last long
dune stabilisation
dunes provide natural barrier, planting vegetation helps keep them in pace
- maintains natural coastal environment
- provides important wildlife habitats
- effective barrier to higher sea levels and tides
- sustainable!
however,
- time consuming
- powerful storms may mean only works for a short while
- areas have to be cornered off reducing tourism
managed retreat
where it is accepted that little can be done to stop flooding/ recession so areas are set aside for sea to flood/ erode (eg creation of marshes)
- allows natural processes to tak eplace uninterrupted
- act as buffer zone to powerful waves (barrier between sea and land)
- can extend current ecosystems
however,
- agricultural land is lost (does not stop land from being lost)
- farmers/ landowners need to be compensated
examples of sustainable management
- managing natural resources (fish, farmland, water supply) to ensure long-term productivity
- managing flood and erosion risk where possible, or relocating to safe areas
- creating alternative livelihoods before existing ones are lost to the sea
- adapting to sea level rise by relocating, alternative building methods and water supplies
- educating communities to understand why change is needed and how to adapt.
- monitoring coastal change and adapting to unexpected trends
