Coastal change and conflict Flashcards
What are discordant coastlines?
- If rock beds run perpendicular to the edge of the sea
- Identifiable by headlands and bays
What are concordant coastlines?
- If rock beds run parallel to the edge of the sea
What can be formed on concordant coastlines?
- Coves and cliffs
How is a cove formed?
- Hard and soft rock must be alternating (concordant coastlines)
- The hard rock cliff face may suddenly crack as erosion weakens a section of the cliffs
- Over time, the hard rock erodes to expose the less resistant rock behind it
- The less resistant rock erodes much quicker than the hard rock, so the cove widens more in the soft rock band
- Erosion continues to widen the cove, but it can’t extend further inland due to another band of hard rock
What are joints and faults?
Joints- small vertical cracks found in nearly all rocks
Faults- larger cracks where a rock has moved, often from past tectonic activity
What are the five coastal processes?
- Erosion
- Weathering
- Transportation
- Mass movement
- Deposition
What are the five erosion processes?
Corrasion
Abrasion
Attrition
Hydraulic action
Corrosion
What is corrasion?
- Sand and pebbles are picked up by the sea and hurled against the cliffs at high tide, causing the cliffs to be eroded
What is abrasion?
- Where sediment scrapes and bangs against the base of a rockface and so gradually wears it away
What is attrition?
- Wave action causes rocks and pebbles to hit against each other, wearing each other down so becoming smaller and rounder
What is hydraulic action?
- As a wave crashes into a cliff or rock face, air is forced into cracks within the rocks
- The high pressure causes the cracks to force apart and widen when the wave retreats and the air expands- over time this causes the rocks to fracture
What is corrosion?
- Mildly acidic sea water can cause alkaline rock such as limestone to be eroded
How are caves, arches, stacks and stumps formed?
- Marine erosion widens cracks in the base of the headland, these get bigger over time and create a cave
- The cave widens and deepens due to marine erosion and sub-aerial processes, and eventually a large hole will form through to the other side of the headland- an arch
- The arch continues to widen until it is unable to support itself, the top falls and a stack is formed
- Marine erosion effects the base of the stack, and eventually it will collapse into a stump
What are wave cut notches and platforms?
- Marine erosion attacks the base of a cliff, creating a notch of eroded material between high tide height and low tide height
- As the notch becomes deeper the cliff becomes unstable and falls under its own weight
- This leaves behind a platform of the unaffected cliff base beneath the wave cut notch
What are the characteristics of constructive waves?
- Strong swash
- Weak backwash
- Low wave height
- Large wavelength
- Low frequency
- Depositional
What is swash?
- The force of the waves travelling up a beach
What are the characteristics of destructive waves?
- Strong backwash
- Weak swash
- High wave-height
- Small wavelength
- High frequency
- Erosional
What type of beaches are hit by destructive waves normally?
- Typically have rocky headlands and landforms, such as tall cliffs and coves
What type of beaches are normally hit by constructive waves?
- Tend to be sandy beaches
What is fetch?
- The length of water over which the wind has travelled
What affects the size of a wave?
- Strength of the wind
- How long the wind has been blowing for
- Water depth
- Distance of fetch
Describe the process of longshore drift:
- Waves hit the beach at angle determined by the direction of prevailing winds
- The waves push sediment in this direction and up the beach in the swash
- Due to gravity, the wave then carries sediment back down the beach in backwash
- This moves sediment along the beach over time
What is deposition?
- Occurs when a wave loses energy meaning the sediment becomes too heavy to carry
What are different types of depositional landforms?
- Beaches
- Spits
- Bars
What are beaches?
- Large deposits of sand and shingle
- Caused by constructive waves hitting a coastline
- Beaches typically have berms- ridges where high tide reaches and deposits a ridge of sand and materials
What is a spit?
- A long, narrow strip of land which is formed due to deposition
- Longshore drift occurs along a coastline but as waves lose energy they deposit their sediment, which eventually forms a spit
What can a spit go onto form?
- Prevailing wind direction will change, causing a hook to form
- The sheltered area behind a spit can become a salt marsh
- Bars
What are bars?
- They can be formed from spits, but only in certain locations
- A bar is a spit that has grown across the mouth of a bay- this creates a lagoon, which can eventually become a freshwater lake
- Ocassionally a bar can be made between a spit and an island, which is known as a barrier beach
What are the three types of weathering processes?
- Mechanical
- Chemical
- Biological
Describe mechanical weathering:
- The breakdown of rocks due to the exertion of physical forces
- Such as Freeze Thaw weathering, where water enters cracks in rocks, freezes and expands, which causes cracks to form
Describe chemical weathering:
- Breakdown of rocks through chemical reactions
- Most common type is carbonation, where acid rain reacts with calcium carbonate in rocks to form a chemical compound that can easily be dissolved
What are the different types of mas movement?
Rock falls
Landslides
Mudflow
Rotational slip
Describe the different types of mass movement:
Rock falls
- Occur on sloped cliffs when the rock becomes exposed to mechanical weathering
Landslides
- Water between sheets of rock and the rock face reduces friction and allows large chunks of rock to slide down the cliff
Mudflow
- Saturated soil flows down the face of a hill like a fluid, bulging at the bottom in a lobe
Rotational Slip
- Also known as slumps, soil and rock fragments become saturated with water, and chunks of rock and soil ‘slip’, creating ‘heads’ down the cliff face
What are human activities on the coast?
Housing
Tourism
Business offices
Agriculture
Industry
Why is there housing on the coast?
- Coastal towns and villages are popular to live in due to their natural beauty and quieter lifestyle compared to a city
- However, as demand for coastal housing increases, house prices increase and housing estates develop, meaning towns can lose their charms
Why is there tourism on the coast?
- Coastlines are tourist attractions as many people visit them for holidays, to visit beaches or to do water sports and sea activities
- This can benefit locals as many work within the tourism sector, but lots of tourists can also cause overcrowding and pollution
Why are there business offices on the coast?
- Some offices relocate to the coast to avoid high rent prices in the city centre
- This brings regular income for locals, but new building developments can destroy natural environments and increase the number of people living in and commuting to a place
Describe agriculture on the coast?
- As the price of land at the coast increases, farmers have to increase their profits with what land they have
- This adds pressure to the land, since farmers will be farming more intensively, which can damage vegetation
Why are industries found on the coast?
- Some require a large volume of water during industrial processes
- These sites are of high economic value so must be protected from risks at the coast
What are risks to the coastline?
- Storm surges in areas of low pressure, causing flooding
- Risk of coastal flooding increasing due to global warming
- Increased frequency of extreme weather events due to climate change
- Rising sea levels can increase rate of erosion
Why are some properties more at risk of falling into the sea?
Geology of cliffs
- Soft rock will erode faster than hard rock
Increased weathering on the top of the cliff
- More vegetation growing, lots of walkers trampling rocks, increased cold weather
Type of waves hitting the cliff face
- Destructive waves cause more erosion than constructive
What are the three types of management?
Hard engineering
Soft engineering
Managed retreat
What is hard engineering?
- Using man-made, artificial structures to reduce or halt erosion
- Often very effective at preventing erosion in a desired place, but they’re high cost and have a significant environmental impact due to the use of concrete etc
What is soft engineering?
- Uses more natural materials to reduce erosion
- Aims to complement the physical environment by using natural methods of coastal defence
What is managed retreat?
- Allow erosion rates to carry on unchanged, but instead monitor the rates and try to adapt it in the future
What are economic values that should be considered in management?
- How many jobs depend on the coast?
- Will industry be lost if erosion continues?
- What will insurance costs be?
What are social values that should be considered in management?
- Is the coast historic or a location of cultural importance?
- Do events or festivals happen here?
- Is the coast home to a village or town?
What are environmental values that should be considered in management?
- Are there any rare or endangered species living along the coastline?
- Would nature reserves be at risk?
- Are there any farms at risk?
What are soft engineering projects for coastal management?
- Dune stabilisation
- Beach nourishment
What is dune stablisation?
- Marram grass is planted
- The roots help bind the dunes, protecting land behind
What are the pros and cons of dune stabilisation?
PROS
- Cost effective and creates an important wildlife habitat
- Relatively cheap and minimum impact on the environment
CONS
- Planting is time consuming
- Can be easily damaged in a storm
What is beach nourishment?
- Sand is added to the beach to replace the material lost through erosion and transportation
What are the pros and cons of beach nourishment?
PROS
- Maintains the beach, which is a big tourist attraction
- Blends in with the rest of the beach so it isn’t unattractive
CONS
- Large quantities of sand needed on a regular basis
What are 4 forms of hard engineering?
Groynes
Sea Walls
Rock armour
Revetments
What are groynes?
Timber or rock protrusions that trap sediment from long shore drift
What are the pros and cons of groynes?
PROS
- Build up beach, protecting cliff and increasing tourist potential
- Cost effective
CONS
- Visually unappealing
- Deprives areas downwind of sediment increasing erosion elsewhere
What are seawalls?
Concrete structures that absorb and reflect wave energy, with curved surfaces
What are the pros and cons of seawalls?
PROS
- Effective erosion prevention
- Promenade has tourist benefits
CONS
- Visually unappealing
- Expensive to construct and maintain
- Wave energy reflected elsewhere, with impacts on erosion rates
What is rock armour?
Large rocks that reduce wave energy, but allow water to flow through
What are the pros and cons of rock armour?
PROS
- Cost effective
CONS
- Rocks are sourced from elsewhere so don’t fit with natural geology
- Pose a hazard if climbed on
What are revetments?
Wooden or concrete ramps that help absorb wave energy
What are the pros and cons of revetments?
PROS
- Cost effective
CONS
- Visually unappealing
- Can need constant maintenance, which creates an additional cost
