Paper 1) Coastal Environments Flashcards
The coast as a system
The coast is a natural system which means that it is a physical cycle where stores and flows of material and energy are linked together.
Erosion definition
The wearing away of rocks to the sea
How coastal erosions impact the UK
-28% of the UK coastline is eroding at varying speeds
-east - more erosion as rocks are softer
-highest rates up to 3.5 meters a year
Types of erosion processes
-hydraulic action
-corrasion/ abrasien
-solution
-attrition
Hydraulic process
-water is forced into cracks into rock
-air compresses
-wave retreats, compressed air blasts out
-damages rock
Corrasion/ abrasien
-rocks are thrown at the cliff
-when waves are destructive they have enough power to throw materials carried to cliff face
-acts like sandpaper, waves cliff away
Solution (erosion process)
-the sea contains salt. Material broken from cliff are dissolved by salt water in waves
-waves crash at cliff, salt and acids cause the rocks to erode
Attrition
-pieces of rock and pebbles from cliff are thrown around, hit each other
-becomes smooth, round
Swash vs backwash
-Waves towards coast
-waves moving away from coast
Constructive wave characteristics
-low energy
-strong swash
-weak backwash
-low wave height
-wide and flat beach shape
-low frequency (6-8 waves per minute)
Destructive wave characteristics
-high energy
-weak swash
-strong backwash
-high wave height
-steep and narrow beach shape
-high frequency (10-14 waves per minute)
Factors affecting coastal erosion
-rock type
-rock structure
-type of coastline
-type of wave
Factors affecting coastal erosion - rock type
Easily eroded (clay and shale):
-wide beaches
Resistant (limestone and chalk):
-steep cliffs, headlands
Factors affecting coastal erosion - rock structure
-rocks parallel to coastline - concordant
-rocks outcrop at right angles to the coast - discordant
Factors affecting coastal erosion - shape of coastline
-headlands are exposed to full force of the sea
-headlands can protect surrounding bays which can be sheltered from erosion
Factors affecting coastal erosion - type of wave
-Destructive wave
-Constructive wave
Types of transportation processes
-traction
-saltation
-suspension
-solution
Traction
Pebbles, large materials roll along the sea bed
Saltation
Small pieces (shingle, large sand grains) bounced along the sea bed
Suspension
Small particles (silts, clays) suspended in the flow of the water
Solution - transportation process
Minerals in rock (chalk, limestone) dissolved in sea water, not visible
Longshore drift
- The prevailing wind pushes waves up the beach at an 45 angle, picking up beach material in the swash
- As the wave retreats, the backwash drags this material back down the beach at a right angle
- Another wave picks up the material and moves it up the beach again, in the swash
- The backwash moves the material back down the beach
- The process continues and the material is moved along the coastline in a zig-zag motion until it meets a barrier (such as a headland or a groyne) and is deposited
Sediment cell
Sediment moved along the coast by longshore drift appears to form part of a circular cell which leads to it eventually returning updrift.
Dredging of offshore shingle banks can therefore contribute to beach depletion.
Coastal deposition
When material being transported dropped by constructive waves as waves have less energy
Where coastal deposition happens
-swash stronger than backwash
-area of shallow water
-enter a sheltered area (cove, bay)
-little wind
-good supply of material
Weathering definition
The breakdown of rocks by the action of weather such as wind and rain at one place.
-can be chemical, mechanical or biological
-erosion is when that rock can then be transported somewhere else
Mechanical weathering
-where water gets into cracks in the rocks during the day
-at night the temperature drops below freezing and the water turns into ice. It expands by 9-10% and begins to push the rock apart
-during the day, the temperature may rise again and ice in the crack will melt. At night-time the same thing happens
-over time, this repeated process will breakdown the rock
Mechanical weathering - salt crystallization
Salt crystals deposited in cracks and over time it accumulates and applies pressure to crack, crystals expand by 300%
Chemical weathering
-Rainwater mixes with chemicals such as carbon dioxide when it falls through the atmosphere
-this weak acid reacts with rocks containing calcium carbonate such as limestone and chalk
-over many years, the acid dissolves the rock - process called carbonation
Biological weathering
-this weathering is caused by animals and plants
-animals such as rabbits can burrow in cracks, make them bigger, and cause the rock to split over a long time
-lichens and mosses release chemicals that dissolves the rock
Mass movement definition
All downhill movement of material under the influence of gravity. The process causes the cliff to retreat backwards and provides material for the marine process
Slumping
Saturated soil slumps along a curved surface
Landslide
Blocks of rock detach themselves from the cliff and slide downhill along a slide plane
-the rock accumulates at the bottom of the cliff
Rockfall
Fragments of rock break away from the cliff face due to weathering
-A scree slope of falling rock is formed at the bottom of the cliff
Landscapes from deposition
-beaches
-spit
-bars
Beaches
Accumulations of sand, mud and shingle. Material has been eroded and transported from elsewhere, and then deposited by waves in the nearshore, foreshore and backshore zone
Key factors that influence beach profiles
-sediment size - grain size/ percolation rates
-wave energy - constructive/ destructive
-tidal range - storms tend to be more frequent in the winter
Spit definition
A long stretch of sand across a river mouth with one end attached to the mainland
Bar definition
A long stretch of sand stretches across a bay leaving a lagoon behind
Tombolo definition
A long stretch of sand joining an island to the mainland
Barrier definition
Form as waves repeatedly deposit sediment parallel to the shoreline. As waves shift, they can constantly move or disappear
Formation of a spit
- Constructive waves and the swash push sediment up the beach
- Sediment moves along the beach in a zig-zag pattern
- Backwash moves sediment down the beach
- Follows the prevailing wind direction
- Sand and shingle is moved along the coast by longshore drift
- Sediment comes to a change in the direction of the coastline
- Sediment is deposited in sheltered water as the current slows down and there is insufficient energy to carry the sediment
- Coast is sheltered and shallow
- Sediment builds up above the level of the sea
- If a spit grows across the river a bar forms and lagoon
- Saltmarsh and sand dunes build up behind the spit
Sand dune formation
- On shore winds blow sand up the beach to the backshore
- In the backshore, obstacles such as rocks and driftwood block sand movement causing deposits to build over time, creating embryo dunes and foredunes
- Vegetation such as Marram Grass starts to grow and helps to stabilize and binds the sand together
- Over time, the sand dunes migrate inland
Factors needed to sand dune formation
-a plentiful supply of sand
-shallow offshore zone with gentle gradient, where large explosives of sand dry out at low tide
-an extensive backshore area where sand can accumulate
-prevailing onshore winds - vegetation which will help the sand be stable
Concordant coastline
Layers of differing rock types that run parallel to the coast
Discordant coastline
Where bands of different rock type run perpendicular to the coast
What do discordant coastlines form
Have alternating bands of hard and soft rock which form the headlands and bays.
-Hard rocks resists erosion and forms headlands
-soft rock is easily eroded and forms bays
-formation of headlands and bays is called differential erosion
What do concordant coastlines form
-e.g. Lulworth cove
1. outer layer of hard rock is punctured
2. allows the sea to erode the softer rocks behind
3. creates a cove
Formation of a wave-cut platform
- At high tide, waves undercut the base of the cliff by hydraulic action and abrasion, forming a wave cut notch
- Weathering from above causes the unsupported overhang to collapse. This leaves a pile of scree (broken fragments of rock) at the base of the cliff
- The sea transports the collapsed material (scree) further along the coastline
- The process repeats and the cliff retreats from its original position
- The former base of the cliff is left as a wave cut platform. In places, it will be continuously smoothed by shingle grinding over it
Formation of an arch/ stack/ stump
- Hydraulic action occurs, water gets into the cracks and air get compressed. The wave retreats and rocks get damaged
- With more hydraulic action and more mechanical weathering, the crack gets bigger
- Over time, the cracks widen and develop as wave cut notches. Further abrasion and hydraulic action will deepen the notch. A cave forms
- If two caves on either side of the cave meet they will make an arch/ or the cave gets bigger and makes an arch
- The top of the arch has fallen as there is no supporting rock underneath
- There is no land connecting the land to a headland so it is a stack. Subaerial processes continue to weaken the stack from above
- Eventually the exposed stack will collapse to form a stump. The waves crash against it and erodes it until it becomes a stump
What makes coasts attractive to people
-do activities on the beach
-tourism
-fishing and biodiversity
-3 billion people live within 10km of the coast
-busy ports - good economy
Impact of people on the coast - settlement
e.g. Hong Kong
-it is a big port
-countries like the UK send rubbish to HK and Malaysia to be put in landfills
-mass amount of people living here, causing an increase in urbanisation which lead to things like habitat disruption and coastal squeeze
-due to high population, the government reclaims land, which changes the coastline and also disrupts and destroys marine life
Impact of people on the coast - fishing
e.g Scotland
-overfishing causes preys and predators to be removed, and so other animals are also affected, as they are part of the food chain
-fish nets from fishermen can drop into the sea, endangering marine life as they are caught in it. The nets also wash up on the coast
-algae can grow unchecked if the fish population decreases - impacts the coral reefs
-fishing creates jobs and is good for the economy
-decline in marine and coral life can cause people to not travel there and do recreational water activities like scuba diving
Impact of people on the coast - deforestation
e.g. Thailand
-damaging the rainforest causes CO2 to be released into the atmosphere, causing global warming
-loss of animals and ecosystems
-deforestation causes pollution in streams which can kill wild freshwater fish, which is a source of food and money for many people living there
-mangroves, which slow does waves as it passes through it, is cut down so erosion happens quicker
Impact of people on the coast - ports and trade
e.g. Rotterdam
-creates jobs and is very important in the economy as Rotterdam is the biggest port in Europe
-creates noise from ship engines and exhaust of particles and dust
-road and rail traffic from the port area causes additional environmental problems
-dredging
Impact of people on the coast - energy
e.g. Nuclear energy UK
-Pollution and radiation to the people living near it (breathing and lung problems)
-risk of a leak
-produces nuclear waste which takes a long time to become safe
-expensive to build and maintain
Impact of people on the coast - Tourism
-many tourists go to beaches, causing the beaches to have trash that goes into the sea
-more hotels are constructed due to more people coming, which also increases pollution
-huge water consumption from tourists, wastewater dumped into the sea
-tourists produce more waste and use more water than locals
-plastic in the ocean will be accidentally eaten, and the marine life will be in danger
Impact of people on the coast - coastal management
e.g. Norfolk, UK
-helps reduce floods and erosion along the shore
-e.g. sea walls, rock armour, groynes
-help protect people’s homes as the coastlines don’t erode that quickly
-costly, not nice to look at
Example of hard rock and soft rock
Hard rock: limestone, basalt, granite
Soft rock: sand, clay
Igenous vs sedimentary rock
Igeneous rock: volcanic, hard rock
Sedimentary rock: rock and sand deposited, breaks more easily
Joint definition
Small, natural cracks, found in many rocks
Faults definition
Larger cracks caused by tectonic movements in the past
Bedding planes
The line separating one layer of sedimentary rock from the next layer of sedimentary rock
How vegetation affects the coast
-increase biological weathering by producing humic acids when it decays and by roots prising rocks apart.
-act as an insulating blanket, protecting the underlying rocks from weathering and erosion
-stabilises surface against wind erosion and providing habitat for wildlife
-roots of marram grass bind soil together
Coastal dunes
Provide a buffer against coastal hazards (wind erosion, wave overtopping, tidal inundation)
-provide a source of sand to replenish the beach during periods of erosion
-certain grasses planted on sand dunes on purpose to preserve the coastline (marram grass)
Foredunes
-Vegetation on the foredune has to grow in sand that is very low in nutrients and dries out quickly
-It has to cope with exposure to sun, salt and wind-blown sand.
-Spinifex and marram grass are often the first species to colonise the foredune, beginning the process of stabilisation because their roots bind the sand
-Spinifex grass has fine hairs that protect the leaves from wind and blowing sand.
Backdunes
-more protection from wind and salt, allowing small plants and shrubs to become established
-Once the foredune is stabilised, there are opportunities for bigger plants to colonise the backdunes - small trees that have special adaptations to help them cope with low nutrients and dry, salty conditions
-Tough leathery leaves slow down transpiration.
-Behind these grow larger trees which attracts native fauna and increases biodiversity.
-Stable and well-vegetated dunes are a barrier to erosive waves, stop sand from being blown inland, and act as a buffer zone that protects land and property
-Dunes and dune vegetation are easily damaged by human activities such as pedestrian traffic or trail bikes. Board and chain walkways can provide access for people, while allowing dune vegetation to establish or regenerate.
Mangrove features
-trap sediment or offer resistance to waves and currents so that land loss is reduced
-Coastal plants have adapted to live in an environment where they are exposed to salt spray (halophytes), sand blasts, strong winds, high temperatures and flooding
-strong root systems that spread rapidly, allowing them to continue growing if part of the plant is buried or uprooted;
-protective waxy and hairy coverings on their leaves and stems to reduce water loss; and
-growing low to the ground, covering the sand and reducing the impact of high wind conditions.
-Other plants also use succulent leaves to store moisture and have modified leaf shapes and colours to help promote their survival in this harsh environment.
Eustatic definitions
Global sea level change caused by a change in the volume of water in the ocean store.
Isostatic definition
Local scale sea level change caused by a change in the level of the land relative to the level of the sea
Emergence definition
The impact of a relative fall in the sea level (marine regression)
Submergence definition
The impact of a relative rise in sea level (marine transgression)
Eustatic sea level change example
-occurs when there is a global change in the amount of water stored in the oceans
-If the two main ice caps — Greenland and Antarctica — melted, then it is calculated that the oceans would rise by 66 metres.
-This also creates landforms of submergence
Landforms of emergence
-raised sea stack
-raised natural arch
-raised beaches - beach left stranded high on a cliff face after a fall in sea level
Mangrove distribution
-most common in South-East Asia
-mainly found in warm tropical waters and coastal swamps within 30N and S of the equator
-grow in the intertidal zone of the coast (foreshore)
Mangrove characteristics
-tangled roots that grow above ground, form dense thickets
-need high levels of humidity (75-80%)
-need high rainfall per annum (1500-3000mm)
-ideal temp - 27C
-complex root system with a filtration system to keep salt out
-some have snorkel like roots that stick out of the mud to help them take in air
-some use ‘prop’ roots or ‘buttresses’ to keep their trunks upright in the soft sediment at the tidal edge
-roots trap mud, sand, silt which builds up the intertidal zone into the new land
-cannot develop on exposed coast with a lot of wave energy or currents that move sediments which would stop seeds from colonising
-ocean currents - distribute mangrove seeds and help keep areas full of trees
Mangrove - value as a resource
-Valuable nurseries of fish and shellfish, wildlife
-trap silt, create new land
Mangrove - under threat
-Believed that they are disease ridden therefore cleared at a fast rate
-for farming and timber
-pollution, overfishing, deforestation for aquaculture
-clearance for land development particularly in developing countries
Sand dune distribution
-accumulation of sand, shaped into mounds and ridges by the wind
-found at the back of a beach, above the max reach of the tide
-develop best when:
-wide beach, large quantities of sand
-prevailing wind is onshore
-large tidal range to allow time for the sand to dry
Sand dune characteristics
-important ecosystem supporting unique flora and fauna that have adapted to live within the dune system
Sand dune formation
-wind blown sand deposited against an obstruction
-more sand particles caught –> dune grows in size, forming rows at right angles to the prevailing wind
-over time, ridges will be colonized and fixed by vegetation
-first plants have to deal with salinity, lack of moisture, wind, temporary submergence by wind-blown sand, rising sea levels
Sand dune - different types
Embryo dune
-deposition begins
-pioneer species - lyme grass, sea couch
-little soil content, high pH
-very fragile, max 1m
Fore dune
-embryo dune bring some protection against wind
-allows other plants to grow - marram grass
-begins to stabilise dune with root system
-add organic matter to dunes –> more hospitable for plant
-microclimate forms in dune slack (lowest point between two dunes)
-max heigh 5m
Yellow dunes
-initially yellow, darken as organic material increases in the soil
-marram grass dominates, but more flowers, insects found in the dune slacks
-20% of dune exposed
-max height 8m
Grey dunes
-more stable
-less than 10% exposed sand, good biodiversity
-soil acidity, water content increase
-shrubs, bushes appear
-height 8-10m
Mature dunes
-oldest, most stable
-found several hundred metres or more from shoreline
-soil can support variety of flora and fauna
Sand dune - under threat
-vulnerable to erosion
-human activity - recreation (biking, horse riding) –> loss of vegetation
-common to see vulnerable sections of dunes fenced off to prevent public access, or for paths to be laid to prevent people from eroding the dunes further
-sand mining
Salt marsh distribution
-found all over the world, not temperature dependant
-typically flat
-form: where coastal areas are well sheltered, areas behind spits where tidal waters can flow gently and deposit fine sediments
-form in brackish waters (partly salt, partly fresh)
Salt marsh characteristics/ formation
-communities of nonwoody, salt tolerant plants
-sediment deposited
-builds up above sea level
-frequency of tidal flooding ensures soil never dries out and remains muddy and sticky
-halophyte plants begin to colonise
-they die, add nutrients, sediment builds up
-more favourable
-natural buffer against coastal erosion and flooding
Salt marsh - under threat
-reclaimed for agriculture or development
-industrial pollution - they are in estuaries and factories pollute the water
-clearance for development - lead to increased noise and light pollution which may affect wildlife behaviour
Biodiversity definition
The number and variety of organisms found within a specified geographic region
Coral reef distribution
-Large deposits of calcium carbonate build entirely of living organisms called coral polyps
-30N and S latitude of the equator (between topic of capricorn and cancer)
-Western Atlantic, Indo-Pacific oceans
-temperature: no below 18C, best at 23-29C
-light: need light for photosynthesis due to algae (zooxanthellae) that live in their tissue
-water: depth of <25m where sunlight can penetrate
-salinity: marine animals - 32-42% salt water
-wave action - need well oxygenated, clean water
-exposure to air - cannot be exposed to air for too long or they will die
-sediment - clear, clean water - any sediment in the water will block normal feeding patterns by reducing the availability of light affecting photosynthesis
-calcium carbonate - coral reefs take available calcium and carbonate ions from the water to create their structures
-nutrients - nitrates and phosphates are scare and are highly recycled within the coral reef ecosystem
Types of coral reefs
-fringing
-barrier
-atolls
Coral reefs - fringing
-low, narrow bands of coral running parallel to the coast and form around a landmass
Coral reefs - barrier
-Grows close to the shore but they have a lagoon that separates it from the shore
Coral reefs - atoll
-a ring of coral that grows on a submerged volcano or mountain
Ecosystem definition
A biological community of interacting living organisms and their physical environment
Abiotic definition
Factors of the ecosystem which aren’t living - sunlight, temperature, salinity, light
Biotic definition
Factors of the ecosystem that are living - coral, animals, plants, bacteria
3 main stores of the coral reefs
Sea water:
-supplies the nutrients
-filtered out and nutrients absorbed by coral and other organisms
Biomass:
-coral polyps
-seaweeds, fish
Litter:
-dead coral, fish
-enrich sea with nutrients which are filtered out by the coral
Coral bleaching
-corals are stressed by changes in conditions such as temperature, light or nutrients
-they expel the symbiotic algae (zooxanthellae) living in their tissues, causing them to turn completely white
Ocean acidification
-reduction in the pH of the ocean over an extended period of time
-caused by an uptake of CO2 from the atmosphere, caused by the burning of fossil fuels
Human threats to coral reefs
-coral mining: removed for bricks/road fill, sand and limestone for cement, coral sold to tourists
-development: causes erosion, runoff of sediment which reaches the reefs, carries fertilizers and sewage into the oceans, damages coral reefs
-tourism: divers harm the coral by touching polyps, dragging anchors, sunscreen in the water
-aquarium and souvenir
-coral bleaching
-ocean acification
-pollution: urban, industrial waste, agrochemicals, oil spills, sewage
Conservationists vs developers
-developers: want to build on coasts
-conservatists: save coasts
SMP
Shoreline management plan
-advance the line - claim land from the sea
-hold the line - defend where you are
-do nothing - let it be
-managed retreat - let some areas flood and move back
Hard engineering
-tend to be expensive, short-term options
-high impact on the landscape or environment
-unsustainable
-groynes, sea wall, rip rap, gabions
Soft engineering
-less expensive than hard engineering options
-usually long-term
-less impact on the environment
-sustainable
-sand dune regeneration, beach replenishment, cliff regrading, managed retreat, salt marsh creation
Sea wall
-concrete wall curved outwards to deflect the power of the waves
-pros: prevents both erosion and flooding
-cons: expensive to build/ maintain, can be damaged if the material is not maintained, restricts access to the beach, ugly
Groynes
-wood, rock, steel piling built at right angles to the shore, traps beach material being moved by longshore drift
-pros: slows down beach erosion, create wider beaches
-cons: stops material moving down the coast where the material may have been been building up and protecting the base of a cliff elsewhere, starves other beaches of sand, wood groynes need maintenance to prevent wood rot, walking along shore line difficult
Rip rap
Large boulders are piled up to protect a stretch of coast
-pros: cheap construction, works to absorb wave energy from the base of cliff and sea walls
-cons: boulders can erode, dislodged during heavy storms
Gabions
-wire cages filled with stone, concrete, sand
-pros: cheapest form, absorb wave energy
-cons: can break, need to be securely tied down, not as efficient as others
Beach replenishment
-Pumping or dumping sand and shingle back onto a beach to replace eroded material
-pros: Beaches absorb wave energy, widens beach front
-cons: has to be repeated regularly-expensive, can impact sediment transportation down the coast
Sand dune regeneration
-help sand dunes build up by planting marrem grass, fencing people off
-pros: attractive, cheap, works with natural processes of the coast
-cons: time consuming, limits access for people, storms can damage
Cliff regrading
-The angle of a cliff is reduced to reduce mass movement
Pros: prevents sudden loss of large sections of cliff
-slow down wave cut notching at base of cliffs as wave energy is slowed
-cons: does not stop cliff erosion
Managed retreat/ salt marsh creation
-Existing coastal defences are abandoned allowing the sea to flood inland until it reaches higher land or a new line of defences
-pros: not expensive, creates new habitats (salt marshes)
-cons: disruption to people where land and homes are lost, cost of relocation is expensive, compensation to people/ businesses may not be paid
Flooding - prevention
-reduces/ removes risk
-flood defences
-emergency centres on high ground
-early warning systems
-education
-planning
-buffer zones - allows energy in surge to dissipate
Building features to cope with flooding
-elevated
-floor proof with raised foundations
-reinforced barrier
-dry flood proofing - sealing a property so that floodwater cannot enter
-wet flood proofing - allow some flooding of the building
Causes of coastal flooding
-heavy rainfall: Soil becomes saturated, no longer absorb more rainfall. Water builds up above the ground and there is more surface runoff. Water goes into rivers and streams which also flood
-reclaimed land: Low lying, susceptible to sea level rise
-money: not enough money to build coastal defences
-low lying land
Maldives case study
-might be the first country to be completely submerged by sea level rise
-80% of land is below 1m above sea level
-GDP - 165/192 countries (1035 USD)
-protests against the government and political unrest results in an unstable government - less resistant to coastal flooding as coping and recovery systems not in place
-main economic sectors: Fishing and tourism
The Maldives - Social impacts of sea level rise
-nearly 400,000 residents forced to leave the island if the present trend of eustatic sea level rise continues - environmental refugees
-fishing yields half as fishermen depend on coral reefs to fish
-salinization will limit the amount of potable groundwater - increase water insecurity
-vegetation destroyed due to salinization, food production decreases, reduces food security
-3/200 islands have already evacuated, disrupting residents’ lives
The Maldives - Environmental impacts of sea level rise
-as sea level rise, coral reef habitats are destroyed
-tidal surges cause the salinization of land. This destroys natural habitats and vegetation
-islands are at greater risk of hurricanes
The Maldives - Economic impacts of sea level rise
-the tourism industry, accounts for 28% of GDP, will be affected as less tourists are willing to visit a place at increasing risk of coastal flooding/ hurricanes
-fishing is the second largest industry, economy impacted greatly due to salinisation
-5 airports, 128 harbors are concentrated along coastline, then imports and exports will be disrupted, impacting the local economy
