COASTS - PAPER 1 Flashcards
What are the 3 types of weathering?
Weathering - disintegration of a rock in situ (in its original place)
Physical weathering - objects causing the decomposition
Chemical weathering - chemicals causing the decomposition
Biological weathering - organisms causing the decomposition
What is freeze-thaw weathering?
- Water seeps into cracks in the rock
- Water freezing means expansion, and at night, when temperatures are low enough, the rock is wedged apart
- In the day, the ice melts and the water contracts
- Over many cycles, the rock breaks into pieces
What are the 4 types of erosion?
Hydraulic action - water forced into the rocks cracking under pressure
Abrasion - sediment in the water scratching rock at the surface
Attrition - particles grinding each other down, creating smooth pebbles
Solution - material dissolving into the water
What are the 4 types of mass movement?
Mass movement - movement of rocks under the influence of gravity
Sliding - Saturated material falling down a slip plane in a straight path down the cliff
Slumping - Sliding, but slumping has a concave slip plane
Mudflow - saturated (full of water) material like clay flowing downhill
Rockfall - individual chunks of rock falling off a cliff face, often because of freeze thaw
What are the 4 types of transportation?
Traction - large particles rolling along the seabed
Saltation - bouncing by pebbles too heavy to be suspended
Suspension - particles suspended in the water
Solution - chemicals dissolved in the water
How do headlands and bays form?
As waves meet the coastline, the rocks at the surface erode at different rates
The soft rocks erode quickly and form bays
The hard rocks erode slowly and jut out forming headlands
How do wavecut platforms form?
- The land slopes to the sea, and freeze thaw weakens the rock
- The base of the cliff erodes by hydraulic action and abrasion
- As erosion continues, more rock breaks off and collects at the base of the cliff
- This forms a notch at the base, that grows over time
- The area under the notch can’t support itself at some point, then falls onto the beach - the steep drop is called a cliff
How do caves, arches and stacks formed?
- Because of hydraulic action, a crack enlarges
- That crack grows into a cave as erosion continues, and the cave increases in size
- An arch forms as the sea breaks through the back of the cave; the base of the arch widens as notches form
- Freeze thaw weakens the top of the arch, and stability decreases
- The top of the arch collapses and a stack forms
- Notches form at the base of the stack, and becomes unstable
- The stack topples, and a stump is left
What are the methods of hard engineering?
Sea walls - a physical barrier placed at the back of a beach, preventing erosion and flooding
Rock armour - many large rocks placed at the back of a beach, reducing the wave’s energy as water enters gaps between rocks
Gabions - mesh cages filled with rocks, absorbing some the wave’s energy as it enters
Groynes - trapping sediment carried by longshore drift, also absorbing the wave’s energy
What are the benefits of hard engineering methods?
Sea walls: Social - can be used as a path for people on top, and also a seating area
Economic - can last for many years
Environmental - Don’t block sediment; doesn’t disadvantage other areas
Groynes: Social - can be used for walking across and acts as a windbreak
Economic - relatively cheap (£5k each), can last up to 40 years; boosts local economy as large beaches attract tourists
Rock armour: Economic - fairly cheap (£1-3k per metre), quick to build and maintenance is simple
Versatile application
Gabions: Economic - relatively cheap (£110 a metre), easy to construct
Can last from 20-25 years
Environmental - blend in to the beach better than other methods
What are the issues with hard engineering methods?
Sea walls: Social - restrict access to the beach, and flooding can occur if waves go over
Economic - £5k per metre to build, expensive repairs
Environmental - can destroy habitats, eyesore for some
Groynes: Social - dangerous to wind surfers, and the barriers stop walking along the beach
Economic - ineffective in stormy conditions, regular maintenance required
Environmental - Considered an eyesore
Rock armour: Social - difficult to access the beach, and accidents could happen
Economic - rocks are taken from overseas; fairly expensive
Regular maintenance required
Environmental - can be seen as an eyesore, and litter can get trapped between the rocks
Gabions: Social - hazardous
Economic - easily degraded, regular maintenance needed
Enviromental - birds can hurt themselves on it, seen as an eyesore
What are the main types of soft engineering strategies?
Beach nourishment - adding sand and pebbles to the beach to absob wave energy, and increasing height/width
Dune regeneration - adding marram grass to stabilise sand dunes, natural buffer to the sea
Managed retreat - allowing the sea to erode the area in a controlled manner
What are the benefits of soft engineering strategies?
Beach nourishment: Social - wider beach means more room for people
Economic - protects expensive properties, and attracts more tourists; decreases maintenance costs for hard engineering strategies
Environmental - natural, blends in with the environment
Dune regeneration: Social - can be used for walking and picnics
Economic - minimal costs; volunteer labour and local plants are used
Environmental - Many species of animal inhabit the dunes
Managed retreat: Social - increased tourism
Economic - low maintenance costs, lasts a long time and sustainable
Environmental - more attractive than most coastal defence, new saltmarsh ecosystem
What are the issues with soft engineering strategies?
Beach nourishment: Social - Access to beach restricted during construction
Economic - Fairly expensive, about £300k to hire a dredger
Environmental - could look unnatural to tourists
Dune regeneration: Social - can deter tourists
Economic - occasional maintenance, and expensive methods to prevent trampling plants
Environmental - plants can be damaged by storms, and can be unstable
Managed retreat: Social - local people can lose land
Economic - can cost millions of pounds, and some farmland can be lost
Environmental - some ecosystems affected by flooding
What is an example of coastal realignment? Why was it done?
Medmerry in West Sussex
Largest coastal realignment scheme in Europe
Prior, it cost £200k yearly to maintain the pebble ridge, and many properties were at risk if water breached
Managed retreat was used, and there was compensation for any residents in the area
A large embankment was placed around the managed area to protect roads and farmland
Rock armour was placed at the edge of the embankment for extra protection
Cost £28m in total
