Coastal Management (Cambridge (CIE) IGCSE Geography) : Revision Note

Coastal defence strategies

• Management of coastal regions is performed by identifying coastal cells

• This technique breaks a long coastline into manageable sections and helps identify two related risks:

  • The risk of erosion and land retreat 

  • The risk of flooding

• Identifying risks allows resources to be used efficiently to limit their impacts

• The 'cost to benefit' is easier to calculate using coastal cells

Prediction

• Early warning systems allow communities to prepare (evacuate or take shelter) before flooding occurs

• Two methods are used to help forecast coastal flooding

  • Past records: diaries, newspapers, government/council records, etc.

  • These identify areas that are at high risk of flooding and their frequency

  • Modern technology: GIS, satellite and computer monitoring, weather stations (local and national), etc.

  • They forecast and track potential hazardous events, such as:

    • Storms: track the storm's path and associated storm surge

    • Earthquakes: the size and position of underwater tremors and possible tsunami outcome

• Both forecasting methods help officials determine when and where the event will occur

• They shows the risk of damage and fatalities as well as the potential intensity and scope of the flooding

Prevention

• Prevention is about taking action that reduces or removes the risk of coastal flooding. Actions include:

Flood defences

• These are built along high-risk stretches of coast 

Emergency centres

• Centrally placed on higher ground where people can be safe from flooding

Early warning systems

• Allows for preparation or evacuation of an area

Education

• Informing local people on what to do if and when a flood occurs

Planning

• Any new development should be planned away from high-risk-areas

• Design buildings to deal with low levels of flooding

  • Raise buildings to allow floodwaters to flow underneath

  • Strengthen barriers

  • Sealing a property to prevent floodwater intrusion is known as dry floodproofing

  • Wet floodproofing allows some flooding of the building

Buffer zones

• Areas of land are allowed to flood before reaching settlements

  • This slows down the floodwater's journey by allowing the surge's energy to dissipate

  • It can mean moving people away from the coast, which could be controversial 

Hard and soft engineering

• There are conflicting views about what type of engineering to use 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 stakeholders' needs

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 a more sustainable approach to coastal protection

• However, they are not as effective as hard engineering methods

  • Areas can just be left at the mercy of the sea

  • More gentle intervention may not be effective

  • People can lose their homes and livelihoods

Beach replenishment

• This is the pumping or dumping of sand and shingle back onto a beach to replace eroded material

• Advantages

  • Beaches are a natural defence against erosion and coastal flooding by absorbing wave energy 

  • Widens beachfront and looks natural

  • Can improve the attractiveness of a stretch of coast

  • Creates a useful amenity for tourism

  • It is a relatively cheap option and easy to maintain

• Disadvantages

  • Has to be repeated regularly, which can be expensive

  • Can impact sediment transportation down the coast

  • People may be prevented from using the beach for several weeks during maintenance

Fencing, hedging, and replacing vegetation

• Helps to stabilise sand dunes or beaches

• Reduces wind erosion

• Advantages

  • Cheap method to protect against flooding and erosion

• Disadvantages

  • Hard to protect larger areas of coastal cliffs

Cliff re-grading

• This is when the angle of a cliff is softened to reduce mass movement

• Advantages

  • Prevents the sudden loss of large sections of cliff

  • As wave energy is slowed, wave-cut notching is reduced at the base of the cliff

• Disadvantages

  • It does not stop cliff erosion; it only slows it down

Beach re-profiling

• Beach re-profiling is the artificial re-shaping of a beach using existing beach material

• Advantages

  • Replaces shingle after winter storms

  • Increasing the profile reduces wave energy before the base of the cliffs

• Disadvantages

  • Re-profiling may have a negative effect on beach habitats

Dune regeneration

• Dune regeneration is the artificial creation of new dunes or the restoration of existing dunes using strategies such as marram grass planting or fencing them off from human impact

• Advantages

  • Sand dunes act as a physical barrier between the sea and the land

  • Dunes absorb wave energy and water

  • This strategy is considered the most natural and can produce an attractive amenity for tourists

  • Dunes may also increase biodiversity by providing a wider range of natural habitats for plants, animals, and birds

• Disadvantages

  • They can be easily damaged by storms

  • Time-consuming to plant the grass and maintain the area

  • It can also deter tourists at this time 

Managed retreat

• The existing coastal defences are abandoned, allowing the sea to flood inland until it reaches higher land or a new line of defences

• Advantages

  • There are no expensive construction costs

  • Creates new habitats such as salt marshes

• Disadvantages

  • Disruptive to people where land and homes are lost

  • The cost of relocation can be expensive

  • Full compensation to people and businesses may not be paid

Hard engineering methods

• Hard engineering involves building concrete, wood, or rock sea defences

• Building and maintaining structures is costly

• Defences work against the power of the waves

• Each defence has pros and cons

• Protection in one place can increase erosion and flooding along the coast

• When settlements and expensive installations (power stations, etc.) are under risk, hard engineering is used because the economic gain outweighs the costs

Sea wall

• A seawall is usually concrete and curved outwards to deflect the power of the waves

• Advantages

  • Most effective at preventing both erosion and flooding (if the wall is high enough)

• Disadvantages

  • Very expensive to build and maintain

  • It can be damaged if the material in front of the wall is not maintained

  • Restricts access to the beach

  • Unsightly to look at

Groynes

• These are wood, rock or steel pilings that are built at right angles to the shore

• Longshore drift moves beach material into groynes

• Advantages

  • Most effective at preventing both erosion and flooding (if the wall is high enough)

• Disadvantages

  • Keeps material from moving down the coast and protects cliff bases elsewhere

  • Starves other beaches of sand

  • Wooden groynes need maintenance to prevent wood rot

  • Makes walking along the shoreline difficult

Rip-rap or rock armour

• Large boulders are piled up to protect a stretch of coast

• Works to absorb wave energy from the base of cliffs and sea walls

• Advantages

  • Cheaper method of construction

• Disadvantages

  • Boulders can be eroded or dislodged during heavy storms

Gabions

• Wire cages are filled with stone, concrete, sand, etc.

• Cages absorb wave energy

• Advantages

  • Cheapest form of coastal defence

  • Can be stacked at the base of a seawall or cliffs

• Disadvantages

  • 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 

• Revetments work to break the force of the waves

• Advantages

  • Traps beach material behind them

  • Set at the base of cliffs or in front of the seawall

  • Cheaper than seawalls but not as effective

• Disadvantages

  • 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 weaken wave energy

• Advantages

  • Beach material is built up

  • Low maintenance

  • Maintains natural beach appearance

• Disadvantages

  • Expensive to build

  • Can be removed in heavy storms

  • Can be unattractive

  • Prevents surfing and sailing

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 or retreat

• Some or all coastal defences are removed, allowing the coastline to move naturally

• Over time the land becomes flooded marshes, effectively protecting the land behind 

• Most natural approach to coastal defence, as it doesn't need maintenance and creates new habitats for animals and plants

• However, the land is lost to the sea, which brings conflict, loss of livelihood and saltwater damages existing ecosystems

• 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