8.4. Coastal Management Strategies Flashcards
Methods of Protecting against Coastal Erosion
- Hard engineering
- Soft engineering
Hard Engineering
Most common way of protecting vulnerable coastlines, which involves building large, solid structures to absorb or reflect the energy of the waves
Types of Hard Engineering
1) Vertical Sea Wall
2) Groynes
3) Breakwater
4) Gabions
Vertical Sea Wall
- Solid, vertical wall of masonry or concrete
- Deep foundations are needed to maintain stability
Vertical Sea Wall Advantages and Disadvantages
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
Groynes
- 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
Groynes Advantages and Disadvantages
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
Breakwater
- 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
Breakwater Advantages and Disadvantages
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
Gabions
- Wire cages filled with stones
- Can be wired together to make any shape or structure
Gabions Advantages and Disadvantages
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
Soft Engineering
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
Beach Nourishment
- Artificial addition of beach material (sand, shingle or pebbles) from another location
- The sediment can be brought by lorry or dredged from offshore
Beach Nourishment Advantages and Disadvantages
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
Sand Dune Conservation
- Important ecosystems
- Provide areas inland from the dunes with protection from coastal erosion and flooding