Coastal landscape and change Flashcards
The littoral zone and the processes in each section
Coastal zones develop between winds waves and currents. the littoral zone consists of 4 sub-categories which include backshore, foreshore, nearshore and offshore.
Backshore- the part of the beach that lies between the beach face and the coastline, often characterised by berms, and is only exposed to waves in extreme events
Foreshore- the zone between high tide levels and low tide levels, long shore drift happens here.
Nearshore- the area of shallow water beyond the low tide mark, this is where waves break and deposition occurs as the waves drop the sediment.
Offshore- the area of deeper water beyond the point at which waves begin to break, offshore bars occur here.
Coastal classification and coastal systems and the factors that influence them.
2 main types of coastal classification which include rocky cliffs and coastal plains
Rocky cliffs- characterised by erosional features
- high energy zone
- rock falls occur here because the cliffs are made from hard rock like chalk or limestone.
Coastal plains- flat, low lying land that is adjacent to the coast
- sandy
- low erosion
- open area
Sediment from rocky cliffs are transported to the coastal plains and deposited there to create a beach or other physical features
Geological structure and how it influences coastal features
Strata- layers of rock
Bedding planes-horizontal cracks, or natural breaks in the strata created during the formation.
Joints-vertical cracks, fractures caused as sediment dries out or during earth movement.
Folds-formed by the pressure during tectonic activity
Faults-when stress and pressure on the rock exceeds the internal strength(faults can slip)
Dips-the angle at which strata lies(horizontally,vertically, dipping towards/away from the sea
Geological structure- how do they influence cliff profiles
The two aspects of geology that influence the coastal landscape are lithology and structure
Lithology- the chemical and physical characteristics of rock types.
Structure- the physical characteristics of rocks, including their jointing, bedding, faulting, angle of dip ect.
Coastal recession- influenced by lithology
- Bedrock is made of indigenous, sedimentary and metamorphic rocks which determines the erosion rates. Harder rocks are more impermeable which lowers the rate of erosion.
- Erosion occurs at the foot of the cliff, creating a notch. the material above the notch becomes too heavy and collapses and its washed away. This cycle repeats and causes the cliff to retreat
- Vegetation stabilise sandy coastlines, provides habitats and flood defences. This is because the roots hold the sand together and stop it from blowing/washing away.
vegetation is important for stabilising the coastlines
- Roots hold the sediment together
- Bind the soil/sand which helps to stabilise the area
- Over time more sediment is deposited
- There is a mild up of sediment which in hand with other things, protects the coastline
- Examples can consist of sand dunes, salt marshes and mud flats
wave types influence beach morphology
Constructive waves
- Swash, going up the beach, is bigger than backwash, going down the beach
- Adds sediment to the area
- Low energy environment
- Shallow beach gradient
Destructive waves
- Backwash, going down the beach, is bigger than the swash, going up the beach
- Takes away sediment from the area
- High energy
- Steep beach gradient
erosional processes lead to different landforms
Hydraulic action-waves hit the front of the cliff and some water gets into the cracks, the pressure then makes the crack expand, this process repeats until the crack gets bigger and turns into caves.
Corrasion- the chemicals in the water dissolve the minerals in the rock and washes it away
Abrasion-rocks rub against the sea bed, which removes small pieces of the rock
Attrition- rocks bash against each other in the water and become smaller and more rounded.
Sediment transfer and deposition lead to different coastal landscapes
Gravity settling- this is when waves are carrying sediment, they become too weak to carry so the large sediments drop first.
Flocculation- small particles like clay being carried by the water. they clump together due to electrical or chemical attraction. they then become very dense and the wave doesn’t have enough energy to carry it so it drops.
The sediment cell and the coastal system
The sediment cell is the complete cycle of sedimentation including source, transport and sinks
Weathering and the coastal system
Biological weathering
-weeds growing through cracks
Mechanical weathering
-Freeze thaw
mass movement and coastal landscapes
Sliding
-Large chunks of rock sliding down a cliff(hard rock)
Slumping
-permiable rock(soft) fills with water and becomes dense and slides down the cliff-clay
Sea level change and landscapes
Eustatic change
- ice caps melting back into the sea and causing sea level to rise
isostatic change
- relates to land rise or downfall
- in the uk, an ice cap used to be in the north which caused the land in Scotland to sink. however now because the ice cap has melted, the land is beginning to rise again which is causing the land in the south to sink.
contemporary sea level change and the risks to coastlines
Kiribati case study
- a group of small islands between the north and South Pacific oceans, practically on the equator
- most land is less that 1 metre above sea level
Coastal recession causes both physical and human
Physical
- ice caps melting
- extreme weather events
human
-part of the reason for climate change
holderness coastline erodes around 2-7 metres each year, due to the easily erodible rock that stretches across the coastline.
-since the roman times, 29 villages have been lost due to coastal recession.
sub aerial processes and rates of erosion
sub aerial processes consist of weathering and mass movement erosion
Rates of erosion rely on the wind direction, tides, season, weather systems and storm occurrence so that makes the rate very inconsistent.
coastal flooding and the local factors that affect the area
location factors such as land height, degree of subsidence and vegetation can increase the risk of flooding, especially in low lying/ estuarine coasts
- Storm surges, tropical cyclones, depression can cause severe coastal flooding risks, which links to social, environmental and economical problems
- Sea level rise affects areas like Kiribati, Tuvalu and Bangladesh
coastal flooding-future uncertanties
Maldives flooding
- loss of land, beaches ect, which causes a loss of tourism and a lack of revenue in the area
- disrupting fishing source
key players
- central government agencies
- local government
- stakeholders in local economy
increasing risks of coastal flooding on local communities
2007
- a flooding in Bangladesh left 9 million people homeless and 1000 people died from drowning or water based diseases
Why does Bangladesh struggle
-due to its location they experience lots of cyclones and heavy monsoon rains
I they have very low lying land and lots of deforestation so they don’t have vegetation to soak up the water and hold the land together
climate change and environmental refugees
Climate change will cause more extreme weather occurrences, for example the ocean temperature needs to be above 27 degrees for a hurricane to form and if temperatures are increasing, that means more water is being heated up
- this will cause and increase of environmental refugees especially from countries like tubal and Bangladesh
- this will cause a knock on affect of higher homelessness rates in certain countries as many of the refugees cannot get jobs
coastal management techniques- hard and soft engineering
Hard engineering- sea wall phase 4 Lyme regis
- man made, usually out of resistant materials like stone or metal
- expensive to build and maintain
- can look ugly and distrust habitats
Soft engineering
- naturally made and imputed to fit in with the environment
- beach nourishment
- cheaper to maintain
- can provide habitats for animals
sustainable management
A policy is being followed in the uk that states they want to move away from hard engineering and replace it with a more sustainable way of protecting coastlines, without damaging habitats and making sure they; - use the last scientific understanding -evaluate new coastal development and -make sure tier inputs are sustainable
Coastal management and iczm
iczm
- individual coastal zone management are planning on focusing on sediment cells and sub divisions to tackle coastal management
- there are 11 sediment cells around the coast of Wales and England
Smp’s
-shore line management plans making sure the whole stretch of the coastline within the cell is protected instead of the isolated approach that was previously used.
coastal management and different policies
Do nothing
Hold the line-sea wall phase 4 Lyme regis
Advance the line- build into water, Dubai ( the palm island)
Retreat the line
