Flashcards in Unit 2: crowded coasts Deck (94):
What physical factors create different coastal environments?
-Different rock types and the process of erosion produce: Cliffs, arches and stacks
-Coastal erosion can also create sheltered inlets and deep natural harbours
-Where big rivers flow into the sea, wide tidal estuaries are formed
-Beaches are formed where the sea deposits eroded material e.g. pebbles or sand
-Flood plains are wide, flat, valley floors that are regularly flooded by a river
-Deltas form at a river mouth when sediment is deposited by the river faster than the sea removes it
-Coastal ecosystems, sucha as mangrove swamps, are valuable natural environments, providing important breeding grounds for many species of fish and shellfish
How do coastal environments encourage different types of development
-Scenery of some coastlines attracts tourists e.g. Jurassic Coast World Heritage Site in Dorset and East Devon attracts thousands of visitors every year
-Natural harbours allow easy access for the import and export of raw materials and manufactured goods by goods which attracts industry to the area
-Estuaries also allow easy access for ships, so encourage port development and attract industry to their hinterlands
-Attractive beaches in areas with equable climate will attract tourists
-Nutrient-rich alluvium deposited by rivers on floodplains and deltas makes the soil very fertile which attracts agriculture
-Some coastal ecosystems have a high biodiversity, which attracts fishing and tourists
Why does increased development cause coastal population growth?
-Physical factors of accessibility, fertile soil, equable climate, dramatic scenery and high biodiversity lead to an increase in fishing, tourism or industry
-fishing and industrial/port development in an area causes an increase in population because people are attracted to live there by the opportunities for employment
-Landis flat by the coast which means homes and businesses can be built much more easily. This encourages people to live and locate businesses in these areas, causing population growth
3 different types of land use model
-Harris and Ullman
What is the Burgess land use model?
-Shows a settlement growing out in concentric zones from the centre
What is the Hoyt land use model?
-Has concentric zones, but adds sectors that grow along linear features, like main roads and rivers
What is the Harris and Ullman land use model?
-Shows multiple nuclei of different land uses.
-It assumes that similar industries with common land use and financial requirements develop near eachother
What 4 ways do coastal developments distort land use models?
How does shape distort land use models?
How does shape distort land use models?
How does shape distort land use models?
How does shape distort land use models?
What are stakeholders?
-Different people who have different ideas on how the development at the coast should take place
What four factors could lead to conflict with stakeholders?
How does tourism cause conflict with stakeholders?
-Tourism brings job opportunities and increased spending in local businesses. However, there can be a conflict between locals and tourists due to traffic congestion, park and noise.
-Environmentally impacts also, as demand for access to tourist areas increases road buildings and construction of other amenities. These may be built on ecologically important land, leading to the construction of valuable coastal ecosystems.
-Tourists can cause coastal erosion by walking over sand dnes and destroying the plants that stabilise the dunes. Causing conflict between toursits and environemental conservationists
How does overfishing lead to conflict between stakeholders?
-Fishing brings jobs and money to coastal areas but overfishing can lead to a rapid decline and extinction of fish populations
-Efforts to conserve fishing stocks cause conflict with the fishing industry. Treaties have been agreed by many countries to impose tariffs to stop fish stocks from collapsing e.g. the EU common Fisheries policy
-This will lead to a decline in jobs and a decrease in fishing communities.
How does aquaculture cause conflict between stakeholders?
-Demand for affordable fish and shellfish has led to the cultivation of aquatic animals in 'fish farms'
-Leads to conflict between producers and environmentalists, due to the potential negative effects aquaculture can have on the surrounding ecosystem
-High levels of fish waste can decrease dissolved oxygen levels in the water, which can lead to the death of other fish and plant life in the area.
-Diseases can spread from farmed fish to wold fish, which can have devastating impacts on the natural population of certain species.
How does industrialisation cause conflict between stakeholders?
-As ports have expanded because of industrial growth, coastal ecosystems have come under threat
-Salt marshes as the coast provide flat land and shleter water, ideal for ports and industry.
-There's a conflict between industry wanting to exploit the advantages of locating at the coast, and those trying to protect salt marshes and other Sites of Special Scientific Interest (SSSIs)
-Pollution of the sea and beaches from industrial waste has harmful effects for swimmers and marine creatures. This causes conflict between the coastal industries who are responsible for much of the pollution and both tourists and environmentalists
3 systems of a coast
What are inputs?
-River sediment, sediment from cliffs that have been eroded or suffered landslides, and sediment that has been transported by waves from offshore
What are processes?
-Wave action, tidal movement, erosion, weathering, transportation. deposition
What are outputs?
-Sediment washed out to sea. or deposited further along the coast
What are Coastal sediment cells?
(Littoral cells) are lengths of coastline that are pretty much entirely self-contained for the movement of sediment.
-So processes in one cell doesn't affect the movement of sediment in another cell
How are waves created?
-Waves are created by the wind blowing over the surface of the sea.
-Friction between the wind and the surface of the sea gives the water a circular motion
How does the effect of the wave depend on height of it.
-Wave hehight is affected by the wind speed and the fetch of the wave.
-The fetch is the maximum distance of sea the wind has blown over in creating the waves
-A high wind speed and a long fetch create high waves
How do waves break at the coast?
Friction witht eh sea bed slows the bottom of the waves and makes their motion more elliptical.
-The crest of the waves rises up and then collapses
-Water washing up the beach is called the ash and water washing back towards the sea is called the backwash
What are the two types of waves?
Characteristics of a constructive waves
-Low frequency )6-8 waves per minute)
-They're low and long which gives them a more elliptical cross profile
-The powerful swash carries material up the beach and deposits it
Characteristics of a destructive wave
-High and steeo, with a more circular cross profile
-They haave a higher frequency (10-14 waves per minute)
-The strong backwash removes material from the beach
What is the purpose of tides?
-Tides affect where waves break
-Tides are the periodic rise and fall of the oceans surface. This is caused by the gravitational pull of the moon and the sun.
-Tides affect the position at which waves break on the beach
-The area between the maximum high tide and minimum low tide is where landforms are created and destroyed
Wat is sub-aerial weathering?
-Describes coastal process that are not linked to the action of the sea. It includes freeze-thaw weathering and salt weathering. Weathering weakens cliffs and makes them more vulnerable to erosion
-Through flow (the flow of water through the cliffs) and runoff (the flow of water over the land caused by heavy rain can also make cliffs more unstable and increases the likelihood of mass movement
-Mass moment is the movement of material downhill due to gravity. It includes landslides, slumping and rockfalls
5 main ways waves erode the coastline
What is abrasion/corrasion?
-Bits of rock, sediment transported by waves smash and grind against rocks and cliffs, breaking bits off and smoothing surfaces
What is hydraulic action?
-Air in cracks in cliffs is compressed when waves crash in.
-The pressure exerted by the compressed air breaks off rock pieces
What is quarrying?
-The energy of a wave as it breaks against a cliff is enough to detach bits of rock
What is corrosion/solution?`
-Soluble rocks (e.g. limestone and chalk) get gradually dissolved by the sea water
What is attrition?
Bits of rock in the water smash against each other and break into smaller bits
What factors affect the rate at which a stretch of coastline is eroded?
-Width of beach
-Breaking point of the waves
-The fetch of the saves
How does width of the beach affect the rate at which a coastline is eroded?
- Beaches slow down waves, reudcing their erosive power.
-A wide flat beach will protect cliffs more than narrow, steeper beahces
How does the breaking point affect the rate at which a coastline is eroded?
-A wave that breaks directly at the foot of a cliff transfers the most energy to the cliff and causes the most erosion.
-Waves that hit the cliff before they break, or break further offshore will erode much less
How does the aspect affect the rate at which a coastline is eroded?
-If the coastline faces the dominant wind and wave direction, erosion will be faster
How does the fetch of the waves affect the rate at which the coastline is eroded?
-Waves with a longer fetch are much higher and steeper, and have more energy, so will cause the most erosion
How does rock type affect the rate at which the coastline is eroded?
-Hard rocks like granite are much more resistant to erosion than softer rocks e.g. clay
What is a current?
Is the general flow of water in one direction
What do currents do?
Currents move material along the coast-by longshore drift
-Swash carries sediment up the beach, parallel to the prevailing wind. Backwash carries sediment back down the beach, at right angles to the shoreline
-When there's an angle between the prevailing wind and the shoreline, a few rounds of swash and backwash move the sediment along the shoreline
What physical factors cause coastal flooding?
-Low pressure atmospheric systems
-Strong onshore winds
-Combination of above factors
How do low atmospheric systems cause flooding?
-Such as hurricanes reduce atmospheric pressure on the sea surface causing it to rise- A storm surge
How do strong onshore winds lead to coastal flooding?
Can force water to high levels along the coast, allowing waves further inland
How do tidal currents cause coastal flooding?
-Tidal currents and surges may be funnelled into a coastal bottleneck such as the bay of bengal forcing sea levels higher
How does high rainfall cause coastal flooding?
-Causes high levels of river discharge. If sea levels at the river mouth is high due to storm surges, the large volume of water may be unable to drain to the sea and can cause flooding
How do a combination of physical factors lead to coastal flooding?
-A hurricane may cause a storm surge and high rainfall which may be unable to drain to sea. The storm surge and wave energy may be both intensified by onshore winds
How do tsunamis cause coastal flooding?
-They are huge ocean waves caused when water is displaced by landslides, volcanic eruptions or submarine earthquakes that shift the ocean floor
-When travelling in open water they have a very small wave height and travel at hundreds of kilometres an hour.
As the waves approach the coast, the bottom of the waves slow considerably due to friction with the sea bed, causing the wave height to increase.
4 human factors that have intensified coastal flooding
-Management of river systems
-Management of coastal systems
-Building on coastal lowlands
-Reclamation of coastal lowlands
How does poor management of river systems led to coastal flooding?
-Dams for example trap sediment and so reduce the amount being deposited at the river's mouth
-This causes deltas and salt marshes to shrink, providing less protection against high tides and storm surges
How does poor management of coastal systems led to coastal flooding?
e.g. coastal defences at Barton have reduced sediment transport to the east, allowing the Hurst Spit to be breached more often, flooding lowlands behind
How does building on coastal lowlands led to coastal flooding?
-especially sand dunes, has restricted sediment supply to protective beaches and marshes.
Development of coastal lowlands, such as Florida, also increases the impact of any coastal floods
How does reclamation of coastal lowlands led to coastal flooding?
-Draining land to reclaim it causes the land to shrink to become lower than sea level.
How is coastal flooding more likely due to rising sea levels?
Onshore winds and low atmospheric pressure systems also cause the sea surface to rise temporarily
-Global sea level rising almost 2mm each year, which is forecast to increase to 4 or 5mm a year by 2100
-This will increase both the frequency and severity of flooding in low-lying coastal areas
What two types of sea level change are there?
What is eustatic sea level change?
Is caused by a change in the volume of water in the sea, or a change in the shape of the ocean basin
What causes eustatic sea level rise?
-Tectonic movements of the earth's crust that alter shapes of ocean basins. E.g. sea floor spreading increases the volume of the basin and so decreases sea level
-Changes in climate: increases in temperature causes melting of ice sheets, which increases sea level. It also causes water to expand, which increases sea level further
-A decrease in temperature causes more precipitation to fall as snow. This increases the volume of water stored in glaciers and so reduces the volume of the sea, which decreases sea level
What is isostatic sea level rise?
-Isostatic sea level change is caused by vertical changes of the land relative to the sea
-Any downward movement of the land causes sea level to rise locally, while the uplift of land causes the sea level to fall.
Causes of isostatic sea level rise
-Tectonic uplift or depression, which occurs mostly at grade boundaries
-Compression or decompression of the Earth's crust due to the accumulation or melting of ice sheets. Slow uplift of land can continue for thousands of years after the weight of a retreating glacier has gone. Accumulation of sediment, mostly at the mouths of major rivers, can also cause compression
-Subsidence of land due to shrinkage after abstraction of groundwater e.g. drainage of marhshland
Impacts of sea level rise
-more frequent and more severe coastal flooding
-Submergence of low-lying islands
-Changes in coastline
Why does sea level rise cause changes in the coastline?
-As sea levels rises, islands are created and the area of land is decreased
What are the 4 options for coastal management?
Holding the line- maintain existing coastal defences
-Advance the line-build new coastal defences further out to sea than the existing line of defence
-Do nothing-build no coastal defences at all, adn deal with the erosion as it happens
-Retreat the line-build no coastal defences, but move people away from the coast
9 different types of hard engineering
How does a sea wall work?
The wall reflects waves back out to sea, preventing erosion of the coast.
-Barrier to prevent flooding
What is the cost and disadvantage of sea walls?
-Cost: Expensive to build and maintain
-Disadvantage: Creates a strong backwash which erodes under the wall
How does a revetment work?
-Slanted sturctures built at the foot of the cliffs.
-Made from concrete, wood or rocks.
-Waves break against the revetments, which absorb the wave energy and so prevent cliff erosion
What is the cost and disadvantage of sea walls?
-Cost: Expensive to build, but relatively cheap to maintain
-Disadvantage: They create a backwash
How do Gabions work?
-Wall of gabions built at the foot of the cliff. They absorb wave energy and reduce erosion
What is the cost and disadvantage of gabions?
How does a rip-rap work?
-Boulders piled up along the coast, the boulders absorb wave erosion so reduce erosion
What is the cost and disadvantage of rip-raps?
-Cost: Fairly cheap
-Disadvantage: Can shift in storms
How do groynes work?
-Fences built at right angles to the coast. They trap beach material transported by longshore drift.
-This creates wider beaches, which slow the waves and so greater protection from flooding and erosion.
What is the cost and disadvantage of groynes?
-They starve down-drift beaches of sand. Thinner beaches dont protect the coast well, leading to greater erosion and flooding.
How do breakwaters work?
-Large concrete blocks or boulders deposited off the coast. The waves energy and erosive power are reduced before they reach the shore
What are the disadvantages and cost of breakwaters?
-Can be damaged in storms
How do earth banks work?
-Mounds of earth act as a barrier to prevent flooding
What are the disadvantages and costs of earth banks?
-Can be eroded
How does a tidal barrier work?
-Built across river estuaries. They contain retractable floodgates that can be raised to prevent flooding
What are the disadvantages and costs of a tidal barrier?
How does a tidal barrage work?
-Dams built across river esutaries. Their main purpose isto generate electricity
-Water is trapped behind the dam at high tide.
-Controlled release of water through turbines in the dam at low tide generates electricity. They also prevent flooding from storm surges.
6 different types of soft engineering.
-Land use management
What is beach nourishment?
-Sand and shingle are added to beaches from elsewhere.
-This creates wide beaches, which reduce erosion of cliffs more than thin beaches
What is beach stabilisation?
-Reducing the slope angle and planting vegetation, or sticking stakes and old tree trunks in the beach to stabilise the sand
-This creates wide beaches, which reduce the erosion of cliffs
What is dune regeneration?
-Sand dunes are created and restored by either nourishment or stabilisation of the sand.
-Sand dunes provide a barrier between land and sea, absorbing wave energy and preventing flooding and erosion
What is land use management? (Soft engineering)
-Vegetation needed to to stabilise the dune can easily be trampled and destroyed, leaving the dune vulnerable to erosion.
-Wooden walkways across dunes, and fenced-off areas, prevent walkers and cyclists damaging vegetation
How is creating marshalnd an example of soft engineering?
-Planting appropriate vegetation (e.g. Glassworts). The vegetation stabilises the sediment, and the stems and leaves help reduce the speed of the waves
-Reduces erosive power of the waves and how far they reach inland
What is coastal realignment (managed retreat)?
-Involves breaching an existing defence, allowing for the sea to flood the land behind.
-Vegetation will colonise the land and it'll become marshland
Why is soft engineering more sustainable than hard engineering?
-Hard engineering often expensive, and disrupts natural processes. Soft engineering require much less time and money to maintain than hard engineering schemes
-Soft engineering integrates the natural environment as it creates areas like marshland, and sand dunes, which are improtant habitats for coastal plants and animals
What is a shoreline management plan (SMP)?
-Is a plan for how a coastline in one sediment cell should be managed. SMP's are developed by local authorites, so that defences in one area dont increase erosion into an adjacent area in the same cell