Coasts Flashcards
1
Q
What are inputs to the coastal system?
A
- Energy (waves, tides and currents)
- Sediment
- Biogenic inputs
- Changes in sea level
- Human activities
2
Q
What are processes in the coastal system?
A
- Erosion
- Longshore drift
- Deposition
3
Q
What are outputs of the Coastal System?
A
- Erosional Landforms
- Depositional Landforms
- Accumulations of sediment above tidal limit
- Loss of wave energy.
4
Q
What are tides caused by?
A
The gravitational pull of the moon as it orbits the earth and the sun as it is orbited by the earth.
5
Q
What is abrasion?
A
The erosion of shore platforms and cliff bases by the constant grinding action of sand, shingle and boulders over rock surfaces.
6
Q
What is attrition?
A
The erosion of the beach material itself, as rocks, boulders and pebbles are constantly knocked against each other in the water.
7
Q
What is biological weathering and erosion?
A
The smoothing of rock, especially shore platforms or the drilling of holes and honeycombs by browsing invertebrates such as limpets, burrowing worms and barnacles. Animals burrowing and tree roots can grow into rock joints.
8
Q
What is corrosion?
A
Salt water from sea spray is able to corrode many rock types. Also, evaporation of salt and the production of crystals which expand in pores and cracks, causes rocks to disintegrate in coastal environments.
9
Q
What is hydraulic action?
A
When pockets of air become trapped and compressed within rock joints or between waves and cliffs. The increased pressure weakens cliff faces and they break.
10
Q
What is rock quarrying?
A
Wave action pulling away loose, jointed rock from cliff faces and shore platforms.
11
Q
What is water layer weathering?
A
The alternate wetting and drying of the shore platform due to tides and waves, causes a variety of weathering processes to take place including hydration, oxidation and salt crystallisation.
12
Q
What is freeze thaw?
A
A type of sub aerial weathering that happens during winter months when water trapped in rock joins or pore spaces within rocks freezes and expands, exerting pressure within the rock. Over time the rock weakens and shatters.
13
Q
What is salt crystallisation?
A
At warm temperatures when water evaporates, salt crystals are left behind that grow and exert pressure within the rock causing it to disintegrate.
14
Q
What are some chemical processes that affect exposed cliffs?
A
- Hydration, minerals absorb water causing them to swell and disintegrate
- Hydrolysis, when H ions in water react with minerals in rocks causing rock to break down.
- Oxidation, occurs when rocks react with oxygen in the air or water, causing the rock to change colour and disintegrate more easily due to a weakened structure.
15
Q
How can human activities contribute to sub aerial weathering?
A
Coastal activities such as rock climbing and mountain biking contribute to increased pressure on coastal paths and may result in footpath and cliff erosion.
Human constructions such as groynes that trap sediment can cause knock on effects down drift, increasing erosion elsewhere.
16
Q
What are the characteristics of constructive waves?
A
-Low height (
17
Q
What are the characteristics of destructive waves?
A
- High (>1m high)
- High frequency (10-14 per minute)
- Short wavelength (about 20m apart)
- Stronger backwash than swash so material is washed back down the beach resulting in flatter beach profiles.
- Steeper gradient
18
Q
How do waves develop?
A
As the wind blows across the surface of the sea, friction causes the water to ripple. As waves form, the surface becomes rougher and it’s easier for the wind to grip the roughened surface and intensify the waves.
19
Q
What are some factors that affect size of waves?
A
- Wind speed
- Fetch
- Gradient of beach
20
Q
How do waves break?
A
The bottom of the wave touches the sand and slows down due to increased friction. The top of the wave becomes higher and steeper until it topples over.
21
Q
What are landforms that are wave dominated?
A
- shore platforms
- cliffs
- beaches
- spits, tombolos
- deltas
22
Q
What are landforms that are tide dominated?
A
- mudflats
- sand flats
- salt marshes
- mangroves
- deltas
23
Q
What landforms are wind dominated?
A
-sand dunes
24
Q
What happens when waves approach an irregular coastline?
A
As the waves approach, they curve and distort. As each wave nears the coast, it drags in the shallow water, causing the wave to become higher and steeper with a shorter wavelength. The part of wave in deeper water moves forward faster, causing the wave to bend. The overall effect is that wave energy becomes concentrated on the headland, causing greater erosion which leads to the development of features such as cliffs, caves and arches. When caves diverge, they lose power and drop their sediment forming beaches.
25
What is a spring tide?
When the moon is between the Earth and the sun, the combined gravitational pull creates the biggest bulge of water and the highest tide. At this time the high tides are at their highest and low tides are at their lowest, so tidal range is at its greatest.
26
What is a neap tide?
When the Earth, moon and the sun form a right angle, their gravitational pulls interfere with one another and this is when neap tides occur giving the lowest high tides and highest low tides (smallest tidal range).
27
What does tidal range impact?
- The vertical difference over which erosion and deposition occur.
- The length of time that the littoral zone (area between high and low water mark) is exposed to sub aerial weathering.
28
How does shape of the coast influence the tidal range?
- Funneled coast e.g. severn estuary = as tide advances it is concentrated in a narrowing space, causing height to rise rapidly, producing a tidal bore.
- Tidal ranges in British Isles are high in places which give a wide zone of wave attack, resulting in the formation of wide wave cut platforms in many places.
- The coriolis effect also influences the range of tides.
29
What is a sediment cell? (littoral cell)
A length of coastline within which the movement is largely self contained. A stretch of coastline within which marine processes or erosion, transportation and deposition operate.
30
What is differential erosion?
Variation in the rates at which rocks wear away.
31
What are joints?
Cracks in the rock, often formed when rocks cool from magma or when materials are offloaded. Joints are usually vertical and increase erosion rates because they represent lines of weakness in the rock.
32
What are bedding planes?
Surfaces that are parallel to surface of deposition. Gaps between planes is an area of structural weakness.
33
What is a concordant coastline?
When the bands of different rock run parallel to the coast. E.g. Durdledoor and the Dalmation Coast in Croatia.
34
What is a discordant coastline?
Where bands of different rock run at rightangles to the coast. E.g the isle of Purbeck, Dorset.
35
How are blowholes formed?
When overlying rocks collapse over a cave and as it is opened up a blow hole can develop.
36
what is the Lithology of rocks?
The characteristics of rocks such as what they are made of and how resistant they are.
37
What is mass movement?
The geomorphic process by which soil and rock move downslope under the force of gravity.
38
When do spring tides occur?
When the sun, moon and Earth are aligned, resulting in a high tidal range.
39
When do neap tides occur?
When the sun and moon are at 90 degrees to eachother and the moon's forces are partially cancelled out by the sun's so the tidal range is reduced.
40
What are the types of mass movement?
- Rockfalls, weathering on rock surfaces breaks rock up into pieces that fall.
- Soil Creep, very slow on shallow slopes soil moves down due to increase in mass when it's wet.
- Landslides, cliffs made from soft rock are lubricated from rainfall so slip.
- Slumping, same as landslides but happens on a concave surface, so the cliff forms a crescent shape.
- Mudflow, occurs on steep slopes with saturated soil and little vegetation to bind soil together
41
What are the types of mass movement?
- Rockfalls, weathering on rock surfaces breaks rock up into pieces that fall.
- Soil Creep, very slow on shallow slopes soil moves down due to increase in mass when it's wet.
- Landslides, cliffs made from soft rock are lubricated from rainfall so slip.
- Slumping, same as landslides but happens on a concave surface, so the cliff forms a crescent shape.
- Mudflow, occurs on steep slopes with saturated soil and little vegetation to bind soil together
42
What are ridges and runnels?
Parallel “hills and valleys” of sand found at the low water mark. These are formed due to the interaction of tides, currents and shallow beach topography and so are often formed as breakpoint bars.
43
What are storm beaches?
A ridge of boulders and shingle found at the back of the beach which have been thrown up to the back of the beach by the largest waves at high tides.
44
What are cusps?
Semicircular depressions formed by waves breaking directly on the beach with a strong swash and backwash
45
What are ripples?
Develop on sandy beaches as a result of wave and tidal movements.
46
What are tides?
The periodic rise and fall of the ocean surface caused by the gravitational pull of the moon and sun.
47
What affects the rate of erosion?
- Width of beach (beach dissipates wave energy)
- breaking point of the waves (if wave breaks close to cliff foot there is more power)
- Aspect (if coastilne faces dominant wave direction erosion is faster)
- fetch (longer fetch means more time for energy to build up)
- rock type (hard rocks are more resistant)
48
What happens in longshore drift?
Swash carries sediment up the beach parallel to prevailing wind. Backwash carries sediment back down at a right angle. It moves sediment along the shoreline.
49
How do cliffs retreat?
Over time cliffs retreat due to action of waves and weathering which can cause a notch to form at the high water mark, which then develops into a cave. Rock above the cave becomes unstable with nothing to support it and collapses.
When a cliff is eroded, flat surfaces are left behind, this is a wave cut platform.
50
How do headlands and bays form?
Headlands and bays form more commonly on discordant coastlines where soft and hard rock occur in layers 90 degrees to the coastline. Differential erosion occurs and the less resistant rock is eroded forming an area sheltered by the more resistant rock sticking out, known as a bay.
The headlands mean wave refraction occurs increasing erosion on headlands and reducing erosion in the bay due to waves losing their energy.
Concordant coastlines can also form bays and headlands but there needs to be a part of the rock that has already been weakened.
51
How are caves, arches and stacks formed?
- Weak areas in the rock such as joints are eroded to form caves. If a cave occurs on a headland, one on the other side can form at the same time and they can eventually meet to form an arch.
- The roof of the arch has no support so is highly susceptible to weathering via exfoliation, salt crystalisation and weathering and may collapse, leaving a stack.
- Stack is very exposed so with time becomes a stump.
52
How do blowholes form?
-Blowholes form in caves when water breaks through the roof due to hydraulic pressure exerting joints in the rocks
53
What is a spit?
A stretch of land or shingle extending from the mainland out to sea parallel to the coastline.
54
How do spits form?
Longshore drift transports sediment along the coastline, and when there is a change in the shape of a coastline such as at the mouth of a river.
Deposition occurs and sand and shingle accumulate. Heavier sediment deposited first, finer material is then deposited as energy is reduced.
As spit grows outwards, a change in wind direction and refraction can result in the curved end of the spit. Salt marshes form in the sheltered low energy area between the spit and the land.
E.g. Spurn head in Yorkshire
55
What is a bar?
If the bay between two headlands is blocked off by a spit, this is known as a bar and the body of water behind is a lagoon.
E.g. Slapton Ley in Devon.
56
What is a tombolo?
When a spit extends out to sea and a coastal island is joined to the mainland. E.g Chesil Beach - joins Isle of Portland to south of mainland Britain.
57
How do saltmarshes form?
They form in low energy environments, where there is shelter from wind and waves. A large input of sediment is required e.g. on a tidal flat, when the periodic flooding of the tidal flat by waves deposits sediment.
Over time sediment accumulates and the tidal flat elevates, reducing duration of tidal flooding allowing a small selection of salt loving plants (pioneer species such as cordgrass and glasswort) to grow on the developing salt marsh.
The vegetation's leaves helps trap sediment building up mud and the roots help stabilise the sediment. Even more plants and animals colonise the salt marsh as the salt marsh's elevation gently increases due to coastal accretion.
58
What are the benefits and negatives of salt marshes?
+produce lovely scenery
+good habitats for many rare creatures
+natural coastal defence
-occur in places sheltered from sea, where people like to build ports for boats
-long plants can get stuck in boat propellers.
Parkgate in Wirral used to be a major shipping potrt but now salt marsh is protected by RSPB.
59
What is a halosere?
An ecological succession that develops in a highly saline environment, most commonly, salt marshes.
60
What is a psammosere?
An ecological succession that develops in the sands of a coastal environment, usually sand dunes.
61
How do sand dunes form?
A large supply of sediment is needed, ideally a tidal flat, where there's a large tidal range and a lot of sand exposed to the wind, ready to be transported. A strong and continuous wind is needed to move sand grains via saltation.
Objects like rocks and human rubbish are deposited on the strandline (high water mark) providing a block to the wind so sand grains are deposited and build upto form an embryo dune. Eventually pioneer species of plants begin to grow, binding together the sand increasing stability. Vegetation also traps sand so embryo dune develops, and a new dune develops in front of it. The old dune becomes a foreduen and the new one is embryo. This is the start of sand dune succession.
62
What are embryo dunes?
The first part of a sand dune succession, that form in the shadow of obstacles at the strandline. Sand is deposited then pioneer species colonise and bind sand together.
Conditions are harsh so plants have adaptations.
high pH of soil limits plant growth. Lack of fresh water means long roots to reach water table which helps stabilise the dune.
63
What are foredunes?
When an old embryo dune is large stabilised and a new embryo dune forms infront of it, it becomes a foredune.
lower pH, tolerable to a wider variety of plants such as Marram grass, which has long roots to bind the sand. Long leaves trap sand.
64
What are grey dunes?
When plant life on a foredune dies, it forms a layer of humus, that is acidic and helps lower the pH of the soil. The high organic content also gives it a grey colour. The soil is now more stable so the dune is fixed.
New plants can now develop.
65
What are dune slacks?
Large depressions in sand dune successions that are often deep enough to expose the water table.
They form when dunes grow large and prevent further deposition of sediment inland by blocking wind.
They can also form as a result of blowouts, when excessive trampling and grazing of plants on a dune reduces its stability so it's easier to erode, and be blown away.
When fresh water is exposed, new types of vegetation can grow.
66
What is a climax of a sand dune?
The end of the sand dune sucession where soil pH is much more acidic due to a thick layer of humus, so shrubs and trees can grow and forests develop.
67
Why and how are sand dunes protected?
Sand dunes are fragile systems susceptible to damage and interference from humans.
Most methods of protection are soft, so they are low cost, low technology and work with nature.
Many sand dunes have restricted access to prevent trampling and increasing the risk of blowouts.
Footpaths are constructed to limit trampling to certain areas, there are boardwalks that allow plants to grow underneath.
Educating tourists is important, with information boards.
68
What is the swash?
A body of foaming water rushing up to the beach.
69
What is wavelength?
Distance between two crests.
70
What is wave period?
The time taken for a wave to travel through one wavelength.
71
What is the trough of a wave?
The lowest point.
72
What is the crest of the wave?
Highest point of the wave.
73
What is the swell?
Waves of low height, gentle steepness, long wavelength and long period.
74
How do waves break?
When the water a wave is travelling in becomes shallow, the normal circular motion of a wave becomes elliptical due to increased friction with the sea bed, so the wave slows down and its height increases, becoming less stable and the wave will break,
75
What are the types of beach profile?
Shingle beaches - steep gradient as waves flow easily through porous surface of beach, decreasing effect of backwash erosion and increasing formation of sediment into a steep slope back.
Sand beaches - typically flatter as smaller particles are evenly distributed so water takes longer to percolate into sand, so more sand is removed with backwash.
76
What are bedding layers?
Rocks tend to form in layers of different types, known as beds, that are subject to tectonic forces that tilt and deform them so they dip at an angle. This effects how they are eroded.
Horizontal beds produce steep cliffs with notches where differential erosion has taken place.
Beds that dip seaward produce gentler cliffs that are less stable as loose material can slide down in mass movements.
Landward dipping beds produce stabler and steeper cliffs.
77
What is eustatic sea level change?
When the sea level changes due to an alteration of water in the oceans or a change in shape of the ocean basin so how much water the sea can hold.
It always has a global effect.
Takes place during or after an ice age. Glacial melt increases sea levels etc.
Increasing temperatures lead to ice sheets melting as well as thermal expansion.
Tectonic movements can change the shape of the ocean basins.
78
What is isostatic sea level change?
The result of an increase or decrease in the height of the land. When land rises, sea level falls, and vice versa.
During an ice age, as ice builds up on land, the weight increases so the land sinks slightly. When ice melts, land rises and this is isostatic rebound.
Tectonic uplift or depression can also cause isostatic sea level change.
79
What are emergent landforms?
They begin to appear at the end of an ice age and occur when isostatic rebound is faster than the eustatic rise in sea level, so features emerge such as raised beaches.
80
What is a raised beach?
Wave cut platforms and beaches that are above the current sea level, as well as relic cliffs behind these raised beaches with relic features such as wave cut notches, arches, stacks, etc that no longer get eroded by the sea, but experience weathering.
81
What are submergent landforms?
They form when the eustatic rise in sea level takes place faster than the isostatic rebound after an ice age, so water floods the land and fills up the landforms.
82
What is a ria?
A feature of submergence. A river valley that has been flooded by the eustatic rise in sea level, similar to a normal river valley just with more water in them.
Cross section of a ria is similar to lower course of a normal river, including the floodplain.
83
What is a Fjord?
A flooded glacial valley. They are relatively narrow for their size and have a U shaped cross profile. They are deep with a shallow mouth where the glacier deposited its load.
E.g. Sogne Fjord in Norway.
84
What is a dalmatian coastline
They form where valleys lie parallel to eachother, and when they are flooded by the rise in sea level, the tops of the valley remain above the surface and appear as a series of islands running parallel to the coastline. E.g. the Dalmation Coast in Croatia.
85
How is sea level changing currently?
We are still coming out of the last ice age - isostatic rebound is still taking place.
Planet is getting hotter (global warming) resulting in ice melting and thermal expansion thus eustatic sea level rise.
So sea level rise can become a problem.
86
How is sea level rise a problem?
In the UK, the East coast is at high risk of being flooded and destroyed, because the sea is rising and land is sinking resulting in more coastal flooding and erosion along the east coast. Many power plants situated along the east coast are at risk, including nuclear power plants which could cause a disaster.
Northern parts of UK are experiencing isostatic rebound and rising above sea level.
87
What are storm surges?
Sudden rises in sea level caused by very strong winds, normally those found in hurricanes and cyclones. The strong winds push the water on an ocean's surface on top of more water, so sea level is higher and coastlines flood.
Conditions needed to create these strong winds include low pressures. Large and powerful waves that can overtop coastal defences can also result in floods.
Storm surges are worse during high tides.
88
How can sea level rise contribute to flooding?
As sea levels rise due to climate change or isostatic rebound, low lying coastal areas are permenantly flooded by the sea. The likelihood and severity of storm surges also rises because weaker winds can increase the sea level enough to flood coastal areas.
89
How do tsunamis result in coastal flooding?
Tsunamis are giant waves that are caused by earthquakes, volcanic eruptions or any type of displacement of water in the ocean.
They travel quicky and are hard to detect so they're very dangerous. As the wave apporaches the shore it slows down but its height increases exponentially without the wave breaking. When it hits the coast, it has a large amount of energy so as it slows even more, it grows taller.
They flood vast expanses of land and cause massive amounts of damage, as they carry debris along with them and they have so much energy.
90
Why is coastal management necesarry?
To protect homes, businesses and natural habitats from being damaged and destroyed by coastal erosion or flooding and to reduce the economic and social effects.
91
What are the four approaches that can be taken in coastal management?
1. Hold the line - maintain existing defenses.
2. Advance the line - new defenses built further out to sea to reduce the stress on current defenses and possible extend the coastline.
3. Retreat the line (surrender) - move people out of danger zones and let the coast do what it will, or break a hole in existing defenses to create areas such as salt marshes to protect the coast further on.
4. Do nothing - deal with the effects of flooding and erosion as they come, This generally happens in areas of low economic value.
92
What are sea walls?
A hard form of engineering where giant concrete walls are put in place to reduce erosion and prevent flooding. They're very expensive as well as big and ugly and require maintenance often. They also produce a strong backwash which undercuts the sea wall which means they are not very sustainable.
Newer sea walls are curved, so waves are reflected back into oncoming waves, reducing erosion.
93
What are groynes.
Hard engineering technique that is wooden walls that extend out to sea. They capture sand and prevent longshore drift, so the beach remains wide to protect the coast from erosion. However land down drift from groynes is deprived of sand so experience worse erosion.
94
What are gabions?
Rocks in a metal mesh that are placed at the base of a cliff to reduce the impact of waves on the cliff. They are designed to reduce the impact of waves on the cliff and prevent undercutting.
They're very cheap but ugly and not particularly effective.
95
What are revetments?
Concrete or sometimes wooden structures built along the base of a cliff. They're slanted and act as a barrier against waves, as revetments absorb the energy preventing cliffs being eroded. They are normally successful but expensive to build. They don't require as much maintenance as a sea wall.
96
What is riprap?
Rocks and stones put against the base of a cliff. Similar to gabions but aren't in a mesh so they look slightly more appealing and blend into the environment but can be moved by the sea.
97
What are breakwaters?
Offshore concrete walls that break incoming waves out at sea so that their erosive power is reduced for when they reach the coast. These are effective but can be easily destroyed during a storm and don't look nice.
98
What is beach nourishment?
When sand and shingle is added to a beach to make it wider, increasing distance a wave has to travel to reach cliffs so the wave's energy will dissipate and its erosive power is reduced. Sand and shingle has to be obtained from elsewhere, normally by dredging.
99
What is land management used for?
To help protect and rebuild dunes. Sand dunes act as a good barrier against coastal flooding and erosion so they can be used as a natural defence. They need to be left undisturbed so boardwalks can be contructed to reduce erosion of dunes by humans.
100
What is marshland creation?
Marshland can be used to break up the waves and reduce their speed and erosive power. Marshlands also limit area which waves can reach preventing flooding. Marshlands can be created by encouraging the growth of marshland vegetation like glassworts.
101
What is beach stabilisation?
Planting dead trees in the sand to stabilise it and lower the profile of the beach while widening it too.
102
Where is Bangladesh and how is it threatened by sea level change?
Bangladesh is located to the East of India, in South Asia, with the bay of Bengal to the south. 80% of the country is a floodplain and part of it is the Ganges delta. The country has been experiencing subsidence, and is very low laying with most of it's area laying only one metre above sea level.
103
What would some social implications of sea level rise in Bangladesh be?
- 0.5m sea level rise could result in 6 million people losing their homes
- rural to urban migration will cause overpopulation in inland cities like Dhaka.
- 60% of protein intake for people is fish, so loss of this can cause health problems
- 18 million people could be displaced by 2050
- increase in transmission of diseases such as cholera.
- Salination of water supplies so there is not enough water for drinking etc.
104
What could be some economic implications of sea level rise in Bangladesh?
- Change of shrimp habitat, losing profits in fishing industry
- Salinity intrusion could drastically reduce rice production
- Bangladesh is a major salt producer, 20 million people employed by the industry so sea level rise would threaten this.
- Loss of coastal beaches and towns may seriously reduce tourism income.
- People could be left unemployed, such as farmers, fishermen and salt producers.
- Forests maintain the ecological balance and are a rich source of firewood, lumber and raw materials, and by 2050 40% could be inundated.
105
What are some environmental impacts of sea level rise in Bangladesh?
- More extreme cyclones could hit Bangladesh as well as more earthquakes etc.
- Aquatic creature's habitats change/
- Coastal wetlands lost to the sea reducing biodiverity and heritage of country.
- Many animals forced to migrate and may become extinct as their habitats are destroyed.
106
What defences do Bangladesh have against sea level rise?
4000km of mud embankments and afforestation are Bangladesh's defences.
Afforestation blocks waves and reduces wind.
Mud banks are said to do more harm than good as they can constrict the width of the delta's estuaries, so high tides are forced to rise higher causing deeper more widespread floods.
Bangladesh is an LEDC so it cannot afford any better flood defences so the best option would be a managed retreat.
107
What are the responses in Bangladesh to sea level rise?
- The government is putting a massive river dredging project in place to increase the capacity of the rivers so more fresh water can be channelled into them reducing salinity.
- In 2009 a climate change strategy was planned to help towards slowing the effects of sea level rise, the plan includes focusing on social security, disaster management, infrastructure development, research and knowledge etc.
108
Explain a case study of coastal flooding.
26th December 2004 a Tsunami struck southern Asia and devestated areas of Indonesia, Sri Lanka, Thailand and India. It was caused by a submarine earthquake in the Indian Ocean and was estimated to measure 9.0 on the Richter scale. The Tsunami travelled across the bay of bengal at speeds of up to 800km an hour. It reached more than 2km inland in the NE of Sri Lanka.
109
What were the social impacts of the 2004 Tsunami?
- Estimated 230000 people killed or missing.
- 1.7 million people made homeless
- Many sources of fresh drinking water were polluted, either by sewage or saltwater.
- An estimated 400,000 lost their jobs in Sri Lanka alone.
110
What were the economic impacts of the 2004 Tsunami?
- Cost of the damage estimated at between $8 - 15 billion.
- Fishing is a large part of the economy for many areas hit by the tsunami and many boats, nets and other equipment were destroyed and lost.
- Salinisation has severely reduced soil fertility so crop yields are lower for years to follow.
- Tourism is important to the economy and 25% of hotels were closed for at least 6 months in Thailand and the number of foreign visitors dropped as the area was perceived to be less safe.
111
What were the environmental impacts of the 2004 Tsunami?
- 8 million litres of oil released into the environment when two oil plants in Indonesia were destroyed.
- Mangrove forests damaged by force of waves and covered in layers of silt.
- High salt content of flood water destroyed the natural balance of many ecosystems such as the Karagan Lagoon in Sri Lanka
112
How had human activity increased the impact of the 2004 flooding in southern Asia?
- Mangrove forests protected parts of the sri Lankan coast by absorbing wave energy, but tourist development and creation of intensive prawn fisheries had meant many mangrove forests had been destroyed so waves could reach further inland.
- Coral reefs surrounding the Maldives acted as a breakwater and prevented complete destruction of the low laying islands, but in other places illegal coral mining and use of dynamite has destroyed many offshore coral reefs in the Indian Ocean reducing level of natural protection from the waves.
113
What is a storm surge?
When a low pressure atmospheric system such as hurricanes reduce atmospheric pressure on the sea surface causing it to rise.
114
What is a cost benefit analysis?
A decision making technique that involves putting a price on all outcomes whether indirect or direct.
It can be used by forming a net benefit and using this as a basis for the decision for protecting a selection of coastline.
115
What is a feasibility study?
Looking at the technical merits of a site and whether the geology etc. is suited.
116
What is a risk assessment?
Involves taking decisions in the light of the likely recurrence interval and what is at risk.
117
Where is the Holderness coastline?
61km of coast stretching from Flamborough Head to Spurn Head in east Yorkshire. It is the fastest eroding coastline in Europe at around 2 metres per year and since Roman times, at least 30 villages have been lost.
118
Why is Holderness so affected by erosion?
- The cliffs are made of mostly soft glacial material called boulder clay that is easily eroded through corrasion and prone to slumping when wet.
- Holderness Coast is very exposed so approaching waves have a long fetch over the North Sea. Also the coast faces the dominant wind direction from the North-East, so waves are very powerful and mainly destructive eroding the base of cliffs.
- Most eroded material is washed out to sea or moved south by longshore drift, as a result beaches are narrow and provide little protection to the land.
- Flamborough Head stops the coast to the south from being replenished and coastal defences are narrowing beaches.
- Further sea level rise due to climate change theatens the coast.
- Attempts to stop erosion in one place have worsened it elsewhere.
119
What are some impacts of coastal erosion in Holderness?
- Properties declined in value as the sea gets closer.
- Around 30 villages lost to the sea since Roman times.
- Caravan parks are losing many pitches each year.
- Large amounts of money is being spent to try and protect the coast (£2 million at Mappelton)
- Gas terminal at Easington is at risk - it provides 25% of Britain's gas and is 25m from the edge.
- 30% decline in tourism due to popular coastal walks disappearing.
- 80,000m^2 of good quality farm land is lost every year.
- West of Easington are several fresh water lagoons which are sites of special scientific interest because of wildlife. Erosion here could mean a flood of salt water destroying the Habitats.
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How is the Holderness coastline protected?
- Bridlington is protected by a 4.7km long sea wall + timber groynes.
- Two rock groynes and a 500m long revetment were built at Mappleton in 1991, they cost £2 million and were built to protect the village and busy coastal B road.
- Withernsea has groynes and a sea wall, with some riprap in front of the wall, after it was damaged in severe storms in 1992.
- At Hornsea there is a concrete sea wall, timber groynes and riprap to protect the village.
- Gabions just south of Hornsea help protect Hornsea Caravan park.
- Easington Gas terminal is proected by a sea wall.
- The eastern side of Spurnhead is protected by groynes and rip rap.
121
How effective has Hard engineering along Holderness been and what are the problems with it?
Hard engineering has been used along a current total of 11.4km of the Holderness coastline, and usually is effective but can have bad effects downdrift.
- Groynes that trap sediment lead to narrower beaches further down increasing erosion. Some farms are considered low value land and at risk of falling into the sea.
- Sediment eroded from Holderness is usually washed into the Humber Estuary where it forms mudflats. Reduced sediment increases risk of flooding and erosion.
- Protection of high value land such as towns is leading to more exposed headlands emerging which will increase the cost of protecting them
- Current schemes are unsustainable.
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What is a case study of soft management?
At Abbots Hall Farm at the Black Water Estuary.
The sea level is rising due to isostatic tilt of the UK as well as eustatic sea level rise so SE England is submerging so coastal flooding is a problem.
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How has coastal flooding been a problem at the Blackwater estuary?
Abbots Hall farm and the surrounding area was protected by a sea wall, as sea levels rose, the salt marsh in front of it was not able to migrate naturally inland so has been drowned out and experienced coastal squeeze.
40% of saltmarsh lost in past 25 years.
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How has coastal flooding been managed at Abbots Hall Farm?
In 2002 the sea wall was deliberatley breached. Sea water flooded land behind.
- 81 hectares of mudflat and saltmarsh was now created.
- Biodiversity increased and saved £500,000 in sea defences.
- Farmland lost, conflict with farmers.
- Sustainable
