Coastal Changes And Conflict Flashcards
When is a discordant coastline created?
When waves hit a coastline composed of hard and soft rock
When are concordant coastlines formed?
When the rock type is the same parallel to the coast
How do coves form?
Wave energy erodes joints and faults in resistant rock and expands them as this section of rock is weaker and easier to erode, the sea then reaches and erodes softer rock behind which can be eroded more quickly than the hard rock
How do headlands and bays form?
On a discordant coastline there are layers of resistant rock and less resistant rock which erode at different rates
How do stumps form?
Cracks are opened up by hydraulic action then grow into a cave by hydraulic action and abrasion which breaks through the headland to form a natural arch, the arch is eroded leaving a stack which is eroded to form a stump
How is a wave cut platform created?
Hydraulic action opens cracks in the rock and this area becomes more resistant to erosion which forms a wave cut notch, the wave cut notch becomes too deep and the cliff face falls but the process of hydraulic action continued which causes the cliff to recede
What happens to the process of erosion on a wave cut platform?
It decreases
What is longshore drift?
The movement of material along the coast by waves which approach it at an angle but recede directly away from it
What is a factor affecting the amount of material deposited by long shore drift?
Amount of wind
When are spits formed?
When longshore drift is fuelled by a strong prevailing wind blowing at an angle to the coastline
What is a spit?
An narrow extended stretch of beach material which projects out to sea and is joined to mainland at one end
When is a spit prevented growing any further?
When the river outlet removes material
Why do recurved laterals form?
Change in wind direction
Why do salt marshes form?
Due to deposition behind spit which is an area sheltered from wind and waves
Why do bars form?
When there is no river to prevent the spit’s movement continuing meaning it extends across a bay and leaves a lagoon behind it
How do storm beaches form?
Found behind normal beaches and are composed of pebbles because storm waves penetrate further and carry heavier sediment
Why don’t sand dunes get blown away?
The grasses planted on them stabilise them
Two examples of ecosystems
Lagoons, marshes
What are 4 negative affects of development on a coastline?
Housing and offices change the look of an area, weight of buildings increases cliff vulnerability, changes in drainage increase saturation, pollution due to increase of people
What are 2 positive affects of development on a coastline?
Money brought to area, raises interest in protecting coastal landscapes
What are 4 negative affects of agriculture on a coastline?
Vegetation changed as it is cleared and crops are grown in its place, soil erosion, increased sedimentation, fertilisers and pesticides seep into local water supplies
What is a positive affect of agriculture on a coastline?
Wildlife habitats created and preserved
What are 3 negative affects of industry on a coastline?
Sea industries locate on the coast which alters the look of an area, cause soil water and air pollution, destroy natural habitats for birds animals and sea life
What is are 2 positive affects of management on a coastline?
Coastal defences slow erosion, some sand dunes and salt marshes and sand bars and spits are preserved
What is a negative affect of management on a coastline?
Stops the supply of sediment through longshore drift to areas further along the coastline
What are two reasons sea levels are rising?
Glaciers melt and water enters seas and oceans, water in seas and oceans is warming which has a larger volume than cold water because the particles vibrate (thermal expansion)
When is coastal flooding worst?
When the spring tide and very low pressure coincide for example during a depression or cyclone
What happens to the surface of the sea in low pressure?
The surface domes and wind blows the dome of water towards the land as a storm surge
How often do high tides occur?
Twice a day
How often do spring tides occur?
Twice a month
What is hard engineering?
The use of solid structure to resist the forces of erosion
What is soft engineering?
The use of natural processes to cope with forces of erosion
How does rip rap/rock armour work?
Large rocks at the foot of cliffs absorb and dissipate wave energy, igneous rocks provide most resistance to erosion
How do recurved sea walls work?
Long concrete walls at the base of cliffs absorb wave energy and have a recurved face to reflect it back into the sea
How do groynes work?
Wooden rock or concrete defences stretch from the coastline to the sea and prevent longshore drift so sand builds up on the side of it , widening the beach and creating a buffer between waves and cliffs
How do gabions work?
Wire cages filled with rocks absorb wave energy to reduce erosion as it doesn’t reach the cliff behind
How does beach replenishment work?
The placing of sand and pebbles on a beaver to make is wider
How does slope stabilisation work?
Drains at the top of cliffs remove groundwater, preventing rocks becoming saturated and reduces slumping . Wire mesh placed over cliffs and piles and long nails hold them in place
Give two advantages of rip rap/ rock armour
Can be very cheap (£300 per metre), effective for many years
Give three disadvantages of rip rap/ rock armour
Unattractive, make beach inaccessible, ineffective in storm conditions
Give 3 advantages of recurved sea walls
Effective for many years, make residents feel safe, protects cliffs and buildings
Give three disadvantages of recurved sea walls
Expensive to build and maintain (£3000 per metre), can deflect waves if positioned incorrectly and cause scouring of the sea bed which reduces water clarity, make beach unattractive
Give two advantages of groynes
Effective for many years, keeps beach in place
Give three disadvantages of groynes
Expensive at £5000, look unnatural, disrupts longshore drift therefore exposes other areas of the coastline to erosion
Give an advantage of gabions
Cheaper style of wall at £100 per metre
Give two disadvantages of gabions
Not very strong, if cages break material used in abrasion is added to sea
Give 4 advantages of beach replenishment
Beaches for tourists, quite cheap, look natural, sand reduces wave energy
Give 3 disadvantages of beach replenishment
Sea continues to erode it, needs to be replaced every few years, expensive
Give three advantages of slope stabilisation
Mass movement is less likely, safer on beach, keeps cliffs in place
Give 3 disadvantages of slope stabilisation
Expensive, difficult to install, foot of cliff still needs protection from waves
What are 7 factors to consider when choosing a coastal defence?
Geology, effectiveness, cost, appearance, durability, land use, installation
What is integrated coastal zone management?
A holistic approach that takes into account the needs of different groups of people, economic costs and benefits of current and future strategies, the environment on land and in sea. Involves holding the line, doing nothing, advancing the line or strategic realignment
What does hold the line mean?
Use sea defences to stop erosion so that the coast stays where it is
What does advance the line mean?
Use sea defences to move the coast further into the sea and make more land
What is strategic realignment?
Gradually letting the coast erode and moving people at risk away
Give 2 benefits of strategic realignment
Less maintenance, people and activities move inland
Give four costs of strategic realignment
Evacuation, expensive, lack of tourism, erosion therefore is unpopular with local residents
Define discordant coastline
Rock strata is at right angles to the coast
What is the difference between joints and faults?
Joints are small cracks in rock, faults are large cracks
Identify 5 factors which determine rate of coastal erosion
Geology most important (soft rock eroded faster than hard), geological structure (whether soft and hard rockjs occur together), ‘wave climate’, local currents and tidal range (difference between low and high tide heights), groundwater levels (saturated cliffs with high groundwater are more vulnerable)
What 4 things does wave climate take into account and how does this increase rate of erosion?
Power of waves, fetch (how far winds travel over open water), wave height, wave direction (destructive waves with a long fetch are more erosive, storms and strong winds increase eroding power of waves)
2 characteristics of a destructive wave
Weak swash and strong backwash so material is dragged back down the beach into the sea
Identify 4 ways waves erode the coast
Solution, attrition, abrasion, hydraulic action
Define abrasion
Breaking waves throw sand and pebbles or boulders at the coast during storms
Define attrition
Rocks and pebbles carried by the waves rub together and break into smaller pieces
Define hydraulic action
Sheer weight and impact of water erodes the coastline, waves compress air in cracks in the rock causing them to expand and weakening the rock
How does the UK climate increase coastal erosion? 3 ways
Four seasons have different impacts on coastal erosion (cold temperatures in winter lead to freeze thaw), prevailing winds are from the south West bringing warm moist air from the Atlantic and frequent rainfall which leads to weathering and mass movement, storm frequency is high in many parts of the UK so coasts are often subject to strong winds leading to an increase in eroding power of waves and also leading to heavy rainfall contributing to mass movement
Define sub aerial processes
Processes that impact on the land (weathering and mass movement)
What kind of weathering is freeze thaw and when is it most effective?
Mechanical. When temperature rises above and falls below 0
When does chemical weathering occur? + 2 examples
When rock’s mineral composition is changed. Granite contains feldspar which converts to soft clay minerals when it reacts with water, limestone dissolved by carbonation (carbon dioxide combines with rainwater to form carbonic acid which changes calcium carbonate into calcium bicarbonate which is carried away by water in solution)
Define mass movement
Downhill movement of material under the influence of gravity. Different typed of mass movement depend on: material involved, amount of water in material, nature of the movement (falls, slips, slides)
Define coastal retreat
When the coast moves further inland
5 steps of longshore drift
Waves approach coast at angle, swash pushes sand and gravel up beach at same angle, backwash carries sand and gravel back down beach at 90 degrees to coastline under force of gravity, sand and gravel move along beach in zig zag fashion, sand is lighter than gravel so is carried further up the beach
4 characteristics of constructive waves
Load carried by waves id deposited by these waves which have a strong swash (break gently and carry material up beach), weak backwash (does not erode material already on the beach), are long in relation to their height and their crest breaks forward
Identify 3 factors which influence deposition by reducing the wave’s energy
Calm conditions, sheltered spots like bays, gentle gradient offshore causes friction
What is a beach?
Accumulation of sand and shingle formed by deposition and shaped by erosion, transportation and deposition
Identify 4 ways waves transport material
Traction, solution, suspension, saltation
What is a positive impact of industry on the coast?
Brings wealth and jobs to an area
What are 2 negative affects of tourism on the coast?
Increased development for hotels impacts on natural processes, increased litter and noise and air pollution
What are 2 positive affects of tourism on the coast?
Increased revenue benefits people living there, increased desire to protect and preserve landscape so tourism continues
How does geology influence erosion on the Dorset coastline? 3 points
At Lulworth Cove waves have cut through the resistant Portland stone and eroded into softer sands and costs behind to form a perfect horseshoe shaped cove, Durdle Door is a natural coastal arch carved out of Portland limestone at Lulworth Cove, at Studland Bay the chalk cliffs have been dramatically eroded into a series of stacks and stumps called Old Harry Rocks
How does weathering influence erosion on Dorset’s coastline?
Weather is warm so salt crystal growth is a predominant type of physical weathering (salty water is thrown up by the sea lands in the cliffs, the water evaporates and leaves behind salt which forms crystals which grow and weaken the rocks)
How does industry influence erosion on the Dorset coastline? 7 points
Dredging the seabed for sand and gravel leads to increased erosion along the coastline, many specific tourist resorts such as Bournemouth and Swanage, investment banks such as JP Morgan -this one bank employs 4000 people, Britain’s sixth largest oil field is located at Poole Harbour, high quality limestone is quarried on the isle of Portland, sheltered harbours like Portland provide direct access to the English Channel therefore are major shopping routes for imports/exports to/from Europe, Bournemouth Conference Centre is a service industry that helps to provide year-round jobs
How does climate change increase flood risk in the UK? 3 points
As atmospheric temperature rises it is likely storm frequency and strength will rise which can increase height and strength of waves reaching the coast, increase in heavy rainfall would increase weathering and mass movement, as sea temperatures rise thermal expansion occurs so sea levels rise
Identify 4 future effects on coastlines of climate change
Erosion may increase causing some beaches to disappear, depositional features like spits may be submerged or destroyed, natural ecosystems and habitats may be destroyed, increased risk of coastal retreat and cliff collapse
Identify 6 effects of increased flood risk on people
Storm surges put people at risk of injury or death, psychological impacts of losing homes/livelihoods, settlement need to be moved or defended which will be expensive, coastal tourism may diminish, flooding of rods and damage to railways makes transport more difficult, loss of agricultural land affects food production and economy
How does coastal management affect erosion on the Dorset coastline?
Much of the Dorset coastline is valuable for tourism so has been protected, Swanage Bay and Bournemouth beach both have groynes and a sea wall and use beach replenishment to add sand to the beach
