8.4. Coastal Management Strategies Flashcards

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1
Q

Methods of Protecting against Coastal Erosion

A
  • Hard engineering

- Soft engineering

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2
Q

Hard Engineering

A

Most common way of protecting vulnerable coastlines, which involves building large, solid structures to absorb or reflect the energy of the waves

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3
Q

Types of Hard Engineering

A

1) Vertical Sea Wall
2) Groynes
3) Breakwater
4) Gabions

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4
Q

Vertical Sea Wall

A
  • Solid, vertical wall of masonry or concrete

- Deep foundations are needed to maintain stability

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5
Q

Vertical Sea Wall Advantages and Disadvantages

A

Advantages

  • Solid structure that can withstand severe wave action
  • Maintains the line of the coastline

Disadvantages

  • High initial costs and high maintenance costs
  • Reduced access to beach - steps have to be provided at regular intervals
  • Basal scour is a problem
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6
Q

Groynes

A
  • Usually of wood - a barrier of stout timber piles and planks built at right angles to the shore
  • They control longshore drift and encourage deposition of beach material
  • Can be made out of stones
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7
Q

Groynes Advantages and Disadvantages

A

Advantages

  • Relatively cheap, but actual cost depends on length and spacing
  • Encourages deposition of beach material, therefore making a wider beach which absorbs wave energy and encourages tourists

Disadvantages

  • Only last 20 years so the maintenance costs are high
  • Visually unappealing and rock groynes are dangerous if people walk on them
  • Interfere with longshore drift so they can cause problems downdrift where beaches are depleted of sediment and erosion rates increase there
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8
Q

Breakwater

A
  • Solid Structure made of masonry with a concrete caps
  • Foundations go down to the bedrock
  • They deflect waves and provide a sheltered environment behind them
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9
Q

Breakwater Advantages and Disadvantages

A

Advantages

  • Protects the area behind them from wave action, reducing erosion and providing a sheltered harbour for small boats
  • Slows longshore drift and encourages a build-up of sediment

Disadvantages

  • Very expensive to build as they are broad and deep
  • Maintenance expensive
  • Basal scour is a problem
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10
Q

Gabions

A
  • Wire cages filled with stones

- Can be wired together to make any shape or structure

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11
Q

Gabions Advantages and Disadvantages

A

Advantages

  • Cheap to build
  • Very flexible as they can be used to produce different shapes and structures

Disadvantages
- Very short lifespan - often no more than 5 years and maintenance costs are high
Unsightly and the wire can be dangerous once it rusts and the gabions burst
- If used as a sea wall they reduce access to the beach

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12
Q

Soft Engineering

A

These strategies are becoming more popular as our understanding of coastal processes improves. It involves working with nature to protect the coast by enhancing the natural, protective, coastal processes

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13
Q

Beach Nourishment

A
  • Artificial addition of beach material (sand, shingle or pebbles) from another location
  • The sediment can be brought by lorry or dredged from offshore
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14
Q

Beach Nourishment Advantages and Disadvantages

A

Advantages

  • Builds up the beach, making it a bigger buffer to absorb wave energy
  • Low initial costs - but this depends on how far the sediment has to be moved
  • Bigger beach attracts tourists
  • Natural and aesthetically pleasing

Disadvantages

  • Requires constant maintenance, especially if longshore drift is vigorously removing the added sediment
  • Often needs groynes to be built downdrift to reduce sediment loss
  • Considerable local disruption during construction phase
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15
Q

Sand Dune Conservation

A
  • Important ecosystems

- Provide areas inland from the dunes with protection from coastal erosion and flooding

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16
Q

Sand Dune Conservation Advantages and Disadvantages

A

Advantages

  • Working with nature to protect an important coastal ecosystem as well as enhancing the natural protection that dunes provide
  • Well-managed systems allow access to the dunes and the beach beyond without excess trampling

Disadvantages

  • Initial costs may be quite high
  • Maintenance is required
  • Some areas of damaged dunes may need to be fenced-off, denying the public access
17
Q

Cliff drainage

A
  • Drainage pipes are inserted into the face of the cliff, especially where the cliff is made of soft or unconsolidated material
  • This removes water from the cliff, lessening the potential for mass movements
18
Q

Cliff drainage Advantages and Disadvantages

A

Advantages

  • The cliff becomes dryer and less prone to slumping
  • Very little environmental impact apart from during the construction phase
  • Maintains the natural appearance and recreational value of the beach

Disadvantages

  • Can be expensive
  • Disruptive and unsightly during construction phase
19
Q

Cliff Regrading

A
  • A vertical cliff is turned into a more gently-sloping cliff by removing material from the cliff top and adding it to the bottom of the cliff (on the beach)
  • Works best in unconsolidated or soft cliff material
20
Q

Cliff Regrading Advantages and Disadvantages

A

Advantages

  • The cliff becomes more stable and less prone to unexpected movements
  • Once ‘naturalised’, the new cliff slope is not unsightly
  • Maintains the natural appearance and recreational value of the beach

Disadvantages
- Often expensive
- Disruptive and unsightly during the construction phase
- Removes the natural cliff line
Major ecological impact e.g. on nesting seabirds

21
Q

Types of Soft Engineering

A

1) Beach Nourishment
2) Sand Dune Conservation
3) Cliff Drainage
4) Cliff Regrading

22
Q

Coastal Flooding

A
  • Very real danger in low-lying coastal areas, especially in deltas and around estuaries
  • Coastal flooding is a common consequence of tropical storms
23
Q

Types of Protection from Coastal Flooding

A

1) Barrages
2) Embankments
3) Shelters

24
Q

Barrages

A
  • Example of a solid, hard-engineering scheme to prevent flooding on major estuaries and other large sea inlets
  • Acts as a dam across an estuary and prevents incursion of seawater either a permanent or temporary basis
  • Only work when combined with embankments on the seaward side, ensuring that high seas can’t outflank them
25
Q

Barrages Advantages and Disadvantages

A

Advantages
- Create a freshwater lake behind them and often encourage the reclamation of land from this lake - encouraging economic development

Disadvantages

  • Very expensive to build
  • Very expensive to build
  • Can destroy feeding grounds of migrating birds and can interfere with fish migration
  • Economically, they can stop the movement of ships to ports further up the estuary
26
Q

Embankments

A
  • Barriers built along the coastline, physically stopping seawater from flooding low-lying land next to the sea
  • Engineers have to decide on a design brief and that usually means protecting against a flood that has a long recurrence interval
27
Q

Shelters

A
  • Cheaper alternative to building embankments
  • Flood-proof shelters which local people can use in the event of a flood
  • Built of concrete and raised above flood level on stilts
  • There has to be a reliable flood warning system in place so that people know when to move to the shelters, but they are capable of saving many lives
  • However, they can’t save people’s homes and livestock and local infrastructure is still at risk
  • This means that, although death is reduced, economic and social disruption is considerable