Edexcel IGCSE Geography 复习笔记 2.3.3 Coastal Management
Edexcel IGCSE Geography 复习笔记 2.3.3 Coastal Management
Coastal Strategies
- Management of coastal regions is performed by identifying coastal cells
- This breaks a long coastline into manageable sections and helps identify two related risks:
- The risk of erosion and land retreat
- The risk of flooding
- Identification allows resources to be allocated effectively to reduce the impacts of these risks
- The 'cost-benefit' is easier to calculate using coastal cells
Shoreline Management Plans
- Shoreline Management Plans (SMP) set out an approach to managing a coastline from flooding and erosional risk
- The plans aim to reduce the risk to people, settlements, agricultural land and natural environments (salt marshes etc.)
- There are four approaches available for coastal management, with differing costs and consequences:
- Hold the line
- Long term approach and the most costly
- Build and maintain coastal defences so the current position of the shoreline remains the same
- Hard engineering is the most dominant method used with soft engineering used to support
- Advance the line
- Build new defences to extend the existing shoreline
- Involves land reclamation
- Hard and soft engineering is used
- Managed realignment
- Coastline is allowed to move naturally
- Processes are monitored and directed when and where necessary
- Most natural approach to coastal defence
- Mostly soft engineering with some hard engineering to support
- Do nothing
- Cheapest method, but most controversial of the options
- The coast is allowed to erode and retreat landward
- No investment is made in protecting the coastline or defending against flooding, regardless of any previous intervention
- Decisions about which approach to apply are complex and depend on:
- Economic value of the resources that would be protected, e.g. land, homes etc
- Engineering solutions - it might not be possible to 'hold the line' for moving landforms such as spits, or unstable cliffs
- Cultural and ecological value of land - historic sites and areas of unusual diversity
- Community pressure - local campaigns to protect the region
- Social value of communities - long-standing, historic communities
Hard Engineering Methods
- Hard engineering involves building some form of sea defence, usually from concrete, wood or rock
- Structures are expensive to build and need to be maintained
- Defences work against the power of the waves
- Each type of defence has its strengths and weaknesses
- Protecting one area can impact regions further along the coast, which results in faster erosion and flooding
- Hard engineering is used when settlements and expensive installations (power stations etc) are at risk - the economic benefit is greater than the costs to build
Hard Engineered Defences
| Strategy | Description | Advantages | Disadvantages |
| Sea Wall | A wall, usually concrete, and curved outwards to deflect the power of the waves | Most effective at preventing both erosion and flooding (if the wall is high enough) | Very expensive to build and maintain
It can be damaged if the material is not maintained in front of the wall Restricts access to the beach Unsightly to look at |
| Groynes | Wood, rock or steel piling built at right angles to the shore, which traps beach material being moved by longshore drift | Slows down beach erosion
Creates wider beaches |
Stops material moving down the coast where the material may have been building up and protecting the base of a cliff elsewhere
Starves other beaches of sand. Wood groynes need maintenance to prevent wood rot Makes walking along the shoreline difficult |
| Rip-rap | Large boulders are piled up to protect a stretch of coast | Cheaper method of construction
Works to absorb wave energy from the base of cliffs and sea walls |
Boulders can be eroded or dislodged during heavy storms |
| Gabions | Wire cages filled with stone, concrete, sand etc | Cheapest form of coastal defence
Cages absorb wave energy Can be stacked at the base of a sea wall or cliffs |
Wire cages can break and they need to be securely tied down
Not as efficient as other coastal defences |
| Revetments | Sloping wooden or concrete fence with an open plank structure | Work to break the force of the waves
Traps beach material behind them Set at the base of cliffs or in front of the sea wall Cheaper than sea walls but not as effective |
Not effective in stormy conditions
Can make beach inaccessible for people Regular maintenance is necessary Visually unattractive |
| Off-shore barriers | Large concrete blocks, rocks and boulders are sunk offshore to alter wave direction and dissipate wave energy | Effective at breaking wave energy before reaching the shore
Beach material is built up Low maintenance Maintains natural beach appearance |
Expensive to build
Can be removed in heavy storms Can be unattractive Prevents surfing and sailing |
Soft Engineering Methods
- Soft engineering works with natural processes rather than against them
- Usually cheaper and do not damage the appearance of the coast
- Considered to be a more sustainable approach to coastal protection
- However, they are not as effective as hard engineering methods
Soft Engineered Defences
| Strategy | Description | Advantages | Disadvantages |
| Beach replenishment | Pumping or dumping sand and shingle back onto a beach to replace eroded material | Beaches absorb wave energy
Widens beach front |
Has be repeated regularly which is expensive
Can impact sediment transportation down the coast |
| Fencing, hedging, and replacing vegetation | Helps to stabilise sand dunes or beaches
Reduces wind erosion |
Cheap method to protect against flooding and erosion | Hard to protect larger areas of coastline cliffs |
| Cliff regrading | The angle of a cliff is reduced to reduce mass movement | Prevents sudden loss of large sections of cliff
Regrading can also slow down wave cut notching at base of cliffs as wave energy is slowed |
Does not stop cliff erosion |
| Managed retreat | Existing coastal defences are abandoned allowing the sea to flood inland until it reaches higher land or a new line of defences | No expensive construction costs
Creates new habitats such as salt marshes |
Disruptive to people where land and homes are lost
Cost of relocation can be expensive Compensation to people and businesses may not be paid |
- There are conflicting views about using a particular type of engineering for coastal defence
- Most coastal managers aim to use a range of methods depending on the value of what is being protected
- This method is known as Integrated Coastal Zone Management (ICZM)
- ICMZ aims to use a combination of methods to best reflect all stakeholder needs
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