8.4 Sustainable management of coasts

• What is sustainable coastal management?


  Managing the wider coastal zone in terms of people and their economic livelihoods, social and cultural well-being, and safety from coastal hazards, as well as minimising environmental and ecological impacts.
• What is a sediment cell? (or littoral cell)


  An area of coastline where sediment is in a closed system (self-contained). Each cell can be broken into smaller sub-cells

  
• How do sediment cells operate?


  • cells are discreet and function separately from each other

  
  

  • the sediment cells are geographically bounded by significant disruptions such as headlands and estuaries

  
  

  • within the cell, sediment is sourced, transferred and stored, coarse sediments are not exchanged between cells, but finer sediment can be

  
  

  • over time, sub-sinks such as beaches and spits will erode and the sediment will re-enter the system

  
  

  • the sediment cell will produce depositional features which are in equilibrium with the amount of sediment available
• Hard engineering:


  Building artificial structures such as sea walls aimed at controlling natural processes of erosion, mass movement or to alter them to protect the coast (such as encouraging deposition)

  Advantages:- overall very successful in protecting coastlines for decades

  Disadvantages:- high costs- makes coastline visually unattractive- Defences built in one place frequently have adverse consequences further along the coast

  
• Soft engineering:


  A sustainable approach to managing the coast without using artificial structures and working with natural environment- less obvious and instrusive, more visually appealing, cheaper in long term.

  1) Beach nourishment:Artificial replenishment of beach sediment to:replace sediment lost by erosion,to enlarge the beachso that it dissipates wave energy and reduces erosion andincreases the amenity value of the beach.

  2) Cliff regrading + drainage: Cliff slope angles reduced to increase stabilityRe-vegetated to reduce surface erosion

  3) Dune stabilisation:Fences are used to reduce wind speeds across the dunes,dunes are then replanted with marram andlymegrass to stabilise the surfaceThis reduces erosion by wind and water.

  4) 'do nothing'

  5) Managed retreat: coastline allowed to retreat at certain places

  
• CASE STUDY: Overview


  Shoreline Management Plan (SMP) of sub-cell 4d 'Beachy Head to Selsey Bill

  
• SMP policies:


  Hold the line:maintain or upgrade the level of protection provided by defences.

  Advance the line:build new defences seaward of the existing defence line

  Managed retreat:allowing retreat of the shoreline, with management to control or limitmovement

  No active intervention:a decision not to invest in providing or maintaining defences
• Overview of SMP of Selsey Bill to Beach head


  Selsey Bill to Beachy Head is a coastline located in the south of the UK

  • 4d sediment

  • affected by erosion and weathering due to longshore drift affecting the coast

  • coast is managed by various types of hard engineering and soft engineering
• Hard engineering: Brighton


  Seaside town that attracts tourists all year round, bringing a total of£380 million per yearto the UK’s GDP from tourism

  •groynesto trap sediment between wooden beams and to prevent backwash•sea wall(original built in 1835 when knowledge of sediment cells was not around) been maintained

  These techniques have been around for 50 years and as a result the groynes are corroding + sea wall is about to collapse

  Management and upkeep of seawall will cost£40 million, sea wall and groynes are unsightly for tourists - tourists could stop visiting due tovisual pollution.
• Evaluation of hard engineering:


  These techniques have efficiently stopped erosion in Brighton – proving that a coast can be managed successfully

  However, this management has caused longshore drift to no longer transport sediment to thebeaches eastward of Brighton Marina,causing these beaches to be washed away as their sediment is no longer being replaced when eroded.

  Management is not sustainable as issue of erosion is solved in Brighton but has caused further erosion and affected livelihoods at Cuckmere.
• Soft engineering: Cuckmere


  - Located between Pevensey and Brighton, another area significantly affected by erosion to the east of Brighton,protective shingle beach is retreating as a result.-100 year SMPproposingmanaged retreat, encouraging the area to naturally rebuild itself- Plan would include letting the area flood and to let mud and sediment build up over time to create saltmarsh lost due erosion.
• Evaluation of management at Cuckmere:


  - Locals opposed to SMP, destruction of property.-A259 roadwould be flooded causing congestion.- Actual benefits of SMP would take 50 years to come into place, would destroy livelihoods in the meantime.- Debatable whether risk of flooding overcomes benefits of fixing Cuckmere’s coast.- Not so sustainable as locals are opposed to the plan.
• Soft engineering: Pevensey


  Small coastal town located eastwards of Brighton.-Beachy Head:9km shingle beach was its own protection until sediment was no longer being replaced as Brighton’s sea walls + groynes stopped longshore drift + lost a large amount of saltmarshes and mudflats from flooding and coastal erosion due to lack- Beach Head is aSSSI(site of scientific special interest) – so must be protected.-Soft engineering:beach replenishment used to build up natural beach again and to stimulate longshore drift to occur again.- However, this caused dust, fumes and noise pollution, irritating locals and wildlife- Now, barges dredge the seabed and ship the sand to the shore to be placed on beach.
• Evaluation of management at Pevensey:


  - Usingbarges was much more sustainable and cheaperas the sand was already on the sea floor so free as it didn’t need to be bought from anywhere, affects locals less.- Tyresalso placed under sand to make the beach more resistant to constructive + destructive waves as the sand stuck in the tyres would make it less vulnerable to erosion.- This was extremely sustainable, reused materials as tyres were taken from landfill.-Stopped erosion at Pevensey for the foreseeable future.
• Conclusion:


  - Hard engineering at Brighton, successfully managed erosion with groynes and sea wall- However, has caused erosion to areas east of Brighton which were originally protected from erosion as sediment cell has been disrupted.- Butmanaging Brighton’s coast is economically sustainable to ensure the tourism industry can continue into the future.- There have been solutions put in place at Pevensey and Cuckmere to protect shingle beaches from erosion.- Issues still need to be sorted in Cuckmere with locals’ retaliation.