Coast Flashcards
4 types of erosions
Abrasion, Attrition, Hydraulic Action, Solution
What is Abrasion
The waves containing eroded materials such as rocks and sand are being throw against the cliff with great force, breaking more rocks off
What is Attrition
Rocks that had been eroded from the cliff falls in the sea. They will collide with each other. Overtime, they become smaller and smoother
What is hydraulic action
Destructive wave repetitively hit against the cliff face until the cliff developes cracks. Overtime, the crack will be windened. Some water will be trapped inside the crack which causes the air of the crack contract, which makes the crack bigger and eventually the rock will break.
What is solution
The acid and salt in sea water reacts with the soluble rock on the cliff face which cause them to dissolve.
What are the four types of marine transportation
Traction - (Stones rolling along the sea-bed)
Supension - (Fine materials being carried by the sea)
Saltation - (Small pebbles bouncing along the sea-bed)
Solution - (Dissolved materials being carried by the sea)
What is mass movement
The downhill movement of material under the influence of gravity
What are the three types of mass-movement?
Slumping
Landslides
Rockfall
What is slumping
When a large area of land on a cliff becomes saturated and heavy “slumps” down the cliff in one peice with the assistance of gravity, leaving a curved surface
What are landslides?
when a section of material slides down a slope, the section of material will stay together until it hits the bottom of the slope
What is rockfall
When fragments of debris break away from a cliff and fall quickly down a cliff- face and land at the bottom of the cliff
explain the formation of a spit
A spit is a depositional landform that forms by longshore drift. The prevailing wind pushes constructive waves up the beach at an angle as the swash. The waves then travel at a 90 degrees angle back down the beach as backwash. This process is repeated and continues down the beach. The beach will then be extended which forms a spit.
3 soft engineering defense methods
- Beach replenishment: Sand is pumped back onto a beach to replace eroded material
- Cliff regrading: The angle of a cliff is reduced to reduce mass movement
- Managed retreat: Existing coast defenses are abandoned allowing the sea to flood inland until it reaches higher land or a new line of defence
Advantages and disadvantages of beach replenishment
Advantages:
- Beaches absorb wave energy,
- Widens beachfront
Disadvantages:
- Has to be repeated regularly which is expensive.
- Can impact sediment transportation down the coast
Disadvantages and Advantages of cliff regrading
Advantages:
-Prevents sudden loss of large sections of cliff
-Regrading can also slow down wave cut notching at the base of cliffs as wave energy is slowed
Disadvantages:
-Does not stop cliff erosion
Advantages and disadvantages of managed retreat
Advantages:
- No expensive constructions cost
- Creates new habitats such as salt marches
Disadvantages:
- Disruptive to people where land and homes are lost
- The cost of relocation can be expensive
Name the six hard engineering strategies for coastal defence
-Sea Wall
-Groynes: Rocks built at right angles to the shore which traps beach material being moved by longshore drift
- Rip Rap: Rocks piled up the protect a stretch of coast
- Gabions: Wired cages filled with stones
- Revetments: Sloping wooden fence with an open plank structure
Tetrapods: Made of concrete which absorbs wave energy
Advantages and disadvantages of Sea wall
Advantages: Most effective at preventing both erosion and flooding
Disadvantages:
-Very expensive to build and maintain
- Restricts access to the beach
- Ugly to look
Advantages and disadvantages of Groynes
Advantages:
-Slows down beach erosion
-Creates wider beaches
Disadvantages:
-Makes walking along the shoreline difficult
-Stops material moving down the coast where the material may have been building upon and protecting the base of a cliff elsewhere
Advantages and disadvantages of Rip-rap
Advantages:
-Cheap
- Works to absorb wave energy from the base of cliffs and sea walls
Disadvantages:
- Rocks can be eroded during heavy storms
advantages and disadvantages of gabions
Advantages:
- Cheap
- Cages absorb wave energy
Disadvantages:
- Wire cages can break and they need to be securely tied down
- Not as efficient as other coastal defenses
Advantages and disadvantages of Revetments
Advantages:
- Breaks the force of the waves
- Cheap
Disadvantages:
- Not effective in stormy conditions
- Can make beach inaccessible for people
- Regular maintenance is necessary
- Ugly
Advantages and disadvantages of tetrapods
advantages:
- Breaks wave energy before reaching the shore
- Low maintenance
disadvantages:
- Expensive to build
- Can be unattractive
- Can be removed easily to prevent storms
