Coastal systems and landscapes Flashcards
(154 cards)
1
Q
What are the inputs to the coastal system?
A
- Marine (waves, tides, salt spray)
- Atmosphere (sun, air pressure, wind speed and direction)
- Human (pollution, recreation, settlement, defences)
2
Q
What are the outputs to the coastal system?
A
- Ocean currents
- Rip tides
- Sediment transfer
- Evaporation
3
Q
What are the stores in a coastal system?
A
- Beaches
- Sand dunes
- Spits
- Bars and tombolos
- Headlands and bays
- Nearshore sediment
- Cliffs
- Wave-cut notches/platforms
- Caves/arches/stacks/stumps
- Salt marshes
- Tidal flats
- Offshore bands and bars
4
Q
What are the flows in the coastal system?
A
- Wind-blown sand
- Mass movement
- Longshore drift
- Weathering
- Erosion (hydraulic action, corrosion, attrition, abrasion)
- Transportation (bedload, suspension, traction, solution)
- Deposition (gravity settling, flocculation)
5
Q
What are the sediment sources for the coastal environment?
A
Rivers, cliff erosion, wind, glaciers, offshore, longshore drift
6
Q
What are sediment cells?
A
Sections of the coast bordered by prominent headlands in which the movement of sediment is almost contained and the glows of sediment act in dynamic equilibrium.
7
Q
What are sediment budgets?
A
Data from inputs, outputs, stores, and flows is used to assess the gains and losses within a sediment cell.
8
Q
How are waves formed?
A
- Winds move across the surface of the water, causing frictional drag which creates small ripples and waves. This leads to a circular orbital motion of water particles in the ocean
- As the seabed becomes shallower towards the coastline, the orbit of the water particles becomes more elliptical, leading to horizontal movement of the waves
- The wave height increases, but the wavelength and wave velocity both decrease
- This causes water to back up from behind the wave until the wave breaks and surges up the beach.
9
Q
What factors affect wave energy?
A
Strength of the wind - the larger the pressure gradient between two areas, the stronger the winds.
Duration of the wind - if the wind is active for longer periods, then the energy of the waves will build up
Size of the fetch - the fetch is the distance over which the wind blows, and the larger it is the more powerful the wave
10
Q
What are the characteristics of constructive waves?
A
- Formed by weather systems that operate in the open ocean
- Long wavelength
- 6-9 per minute
- Low waves, which surge up the beach
- Swash is stronger than the backwash
- Occurs on gently sloped beaches
11
Q
What are the characteristics of destructive waves?
A
- Formed by localised storm events with stronger winds operating closer to the coast
- Short wavelength
- 11-16 per minute
- High waves, which plunge onto the beach
- Swash is weaker than backwash
- Occurs on steeply sloped beaches
12
Q
What is an example of negative feedback for waves?
A
The presence of constructive waves causes deposition on the beach, which in turn leads to the beach profile becoming steeper. Steeper beaches favour the formation of destructive waves which are then more likely to occur. The destructive waves erode the beach, reducing the profile and leading to the formation of constructive waves. As constructive waves occur more frequently in the summer, the beach profile is more gentle in the summer and steeper during the winter.
13
Q
What is the tidal range?
A
The difference in height between the tides. It tends to be largest in channels such as river estuaries.
14
Q
When do spring tides occur?
A
When the sun and the moon are in alignment, so their gravitational forces work together. Spring tides have the largest possible tidal range.
15
Q
When do neap tides occur?
A
When the sun and the moon are perpendicular to each other, so their gravitational forces work against each other. Neap tides have the lowest possible tidal range.
16
Q
How are rip currents formed?
A
Plunging waves cause a build-up of water at the top of the beach. The backwash is forced under the surface due to resistance from breaking waves, forming an underwater current.
17
Q
What are high energy coastlines?
A
High energy coastlines are associated with more powerful waves, so occur in areas where there is a large fetch. They typically have rocky headlands and fairly frequent destructive waves. As a result these coastlines are often eroding as the rate of erosion exceeds the rate of deposition.
18
Q
What are low energy coastlines?
A
Low energy coastlines have less powerful waves and occur in sheltered areas where constructive waves prevail and as a result are often sandy. There are landforms of deposition as the rate of deposition exceeds the rate of erosion.
19
Q
What is wave refraction?
A
The process by which waves turn and lose energy around a headland or uneven coastline. The wave energy is focussed on the headlands, creating erosive features in these areas. The energy is dissipated in bays leading to the formation of features associated with lower energy environments such as beaches.
20
Q
What is an example of negative feedback for erosion?
A
Due to the different rock strengths, erosion leads to the formation of headlands where resistant rock exists and clays where unconsolidated rocks and clays are dominant. This then increases the forces of erosion on the headlands and reduces erosion in the bays, as wave refraction dissipates wave energy and the beach protects the coastline behind.
21
Q
What is erosion?
A
Processes which involve the removal of sediment from a coastline
22
Q
What is abrasion?
A
Sediment carried by the sea is picked up by strong waves and thrown against the coastline causing more material to be broken off and carried by the sea.
23
Q
What is attrition?
A
wave action causes rocks and pebbles to hit against each other, wearing them down and becoming rounder and smaller.
24
Q
What is hydraulic action?
A
As waves crash onto a rock or cliff face, air is forced up into cracks, joints and faults within the rock. The high pressure causes the cracks to spread apart. Over time this causes the rock to fracture. Bubbles found within the water by implode under the high pressure creating tiny jets of water that erode the rock (cavitation).
25
What is corrosion?
The mildly acidic seawater can cause alkaline rock such as limestone to be eroded.
26
What is corrosion?
The mildly acidic seawater can cause alkaline rock such as limestone to be eroded.
27
What factors affect erosion?
- Waves
- Beaches - if there is a beach in front of the cliff it will absorb the wave energy
- Subaerial processes - weathering and mass movement weaken cliffs
- Rock type
- Rock faults
- Lithology
28
What is traction?
large, heavy sediment rolls along the sea bed pushed by currents
29
What is saltation?
smaller sediment bounces along the sea bed, pushed by currents
30
What is suspension?
small sediment is carried within the flow of the water
31
What is solution?
dissolved material is carried within the water, potentially in a chemical form
32
How does longshore drift work?
- Waves hit the beach at an angle determined by the prevailing wind
- The waves push sediment in this direction and up the beach in the swash
- Due to gravity, the wave then carries sediment back down the beach in the backwash
- This moves the sediment along the beach over time
33
What are the two types of deposition?
Gravity settling - the waters velocity decreases so sediment begins to be deposited
Flocculation - clay particles clump together due to chemical attraction and then sink due to their high density.
34
What is weathering?
the breakdown of rocks over time, leading to the transfer of material into the littoral zone, where it becomes an input to sediment cells.
35
What is freeze-thaw weathering?
water enters cracks in the rocks and then the water freezes overnight during the winter. As it freezes, it expands and places pressure on the rock, causing the crack to develop. Over time these cracks grow, making the cliff weak
36
What is salt crystallisation weathering?
as seawater evaporates, salt is left behind. Salt crystals will grow over time, exerting pressure on the rock, which forces the cracks to widen. Salt can also corrode ferrous rock.
37
What is wetting and drying weathering?
rocks such as clay expand when wet and then contract again when drying. The frequent cycles of wetting and drying can cause these rocks to break up.
38
What is carbonation weathering?
rainwater absorbs CO2 from the air to create weak carbonic acid which then reacts with calcium carbonate in rocks to form calcium bicarbonate which is easily dissolved. Acid rain reacts with limestone to form calcium bicarbonate too.
39
What is oxidation weathering?
when minerals become exposed to the air through cracks and fissures, the mineral will become oxidised which will increase its volume, causing the rock to crumble.
40
What is solution weathering?
rock minerals such as rock salt are dissolved
41
What is plant root weathering?
roots grow into the cracks in rocks, which splits the rocks
42
What is bird weathering?
some birds such as puffins dig burrows into cliffs weakening them and making erosion more likely
43
What is rock boring?
many species of clams secrete chemicals that dissolve rocks
44
What is seaweed acid weathering?
some seaweeds (kelp) contain pockets of sulfuric acid, which if hit against a rock or cliff face can dissolve some of the rocks minerals
45
What is decaying vegetation weathering?
water that flows through decaying vegetation and then over coastal areas will be acidic, causing chemical weathering
46
What is an example of positive feedback for weathering?
If the rate of removal of weathered rock from the base of the cliff is higher than the rate of weathering, then this will promote further weathering as this will increase the area of exposed rock. This will increase the amount of erosion that occurs because it will increase the supply of rocks, which can become part of the erosive process.
47
What is an example of negative feedback for weathering?
If the removal of weather rock from the base of the cliff is slower than the rate of weathering then this will lead to a build up of debris at the base of the cliff, reducing the exposed cliff area and therefore reducing the rate of erosion.
48
What are sub-aerial processes?
Land based processes which alter the shape of the coastline. They include the processes of weathering and mass movement.
49
What influences vulnerability to sub-aerial processes?
temperature and climate, as they influence the predominance of weathering.
50
What is mass movement?
The movement of material down a slope under the influence of gravity.
51
What does the type of mass movement depend upon?
- cliff/slope angle
- rock type/structure
- vegetation
- saturation of ground
- presence of weathering
52
What are the types of mass movement?
soil creep, solifluction, mudflows, rockfall, landslide, slumping, runoff
53
What is soil creep?
The slowest but most continuous form of mass movement involving the movement of soil particles downhill. Particles rise and fall due to wetting and freezing, which causes them to move down the slope. Leads to the formation of shallow terraces.
54
What is solifluction?
Mainly in tundra areas where the land is frozen. As the top layers thaw during the summer, the surface layers flow over the frozen layers. Forms solifluction lobes.
55
What are mudflows?
An increase in the water content of soil can reduce friction, leading to earth and mud to flow over underlying bedrock, or slippery materials such as clay. Water can get stuck in the rock, increasing pore water pressure, which forces rock particles apart and therefore weakens the slope.
56
What is rockfall?
Occurs on sloped cliffs when exposed to mechanical weathering. It leads to scree building up at the base of the slope.
57
What are landslides?
Heavy rainfall leads to water between joints and bedding planes in cliffs, which can reduce friction leading to a landslide. It occurs when a block of intact rock moves down the cliff face very quickly along a flat slope.
58
What is slumping?
When the slope is curved, a build up in pore water pressure leads to the land collapsing under its own weight. It creates a terraced appearance to the cliff face.
59
What is runoff?
Overland flow picks up sediment or erodes the cliff face, and then transports it into the littoral zone via suspension.
60
What are some examples of erosional landforms?
- caves, arches, stacks, stumps
- steep cliffs
- gentle cliffs
61
How are caves, arches, stacks, and stumps formed?
- Faults in the headland are eroded by hydraulic action and abrasion to create small caves
- The overlying rock in a cave may collapse, forming a blowhole. The blowhole spurts water when a wave enters at the base, forcing sea spray out the top
- Marine erosion widens faults in the base of the headland, widening over time to create a cave
- The cave will widen due to marine erosion and sub-aerial processes, eroding through to the other side of the headland, creating an arch
- The arch continues to widen until it is unable to support itself, falling under its own weight through mass movement, leaving a stack as one arch becomes detached from the mainland.
- A wave-cut platform will be left afterwards
62
What are the characteristics of a steep cliff?
most common where the rock is strong and resistant to erosion. Sedimentary rocks that have vertical strata are more resistant to erosion. An absence of beach, long fetch, and high energy waves promote steep cliff development.
63
What are the characteristics of gentle cliffs?
most commonly found in areas with weaker rocks which are less resistant to erosion and are prone to slumping. Low energy waves and a short fetch will lead to the formation of a scree mound at the base of the cliff, reducing the overall cliff angle. A large beach reduces wave energy.
64
What affects the rate of retreat for cliffs
depends on the relative importance of marine factors (fetch, beach, wave energy) and terrestrial factors (sub-aerial processes, geology, rock strength). The cliffs most likely to retreat are those made of unconsolidated rock and sands.
65
What is an example of negative feedback for cliff erosion?
during a storm, part of a cliff may collapse so the material produced will protect the base of the cliff from marine erosion, reducing cliff recession. Sand dunes may be eroded during a storm, meaning a loss of sediment on land. However, the sediment produced may be deposited in offshore bars, which protect the coastline from further erosion by dissipating wave energy.
66
How are wave cut platforms/notches formed?
- When waves erode a cliff, the erosion is mostly concentrated around the high tide line. The main processes of hydraulic action and abrasion create a wave cut notch.
- As the notch becomes deeper and sub-aerial processes weaken the cliff from the top, the cliff face becomes unstable and falls under its own weight through mass movement
- This leaves behind a platform of the unaffected cliff base beneath the wave cut notch
- Over time the same processes repeat leading to a wave cut platform, which is exposed at high tide.
67
What is an example of negative feedback for wave cut platforms?
the length of a wave cut platform is limited as eventually the waves can no longer reach the cliff, reducing erosion. Therefore the act of erosion creating the wave cut platform has acted to decrease the rate of erosion in the future.
68
What are the examples of landforms of deposition?
- Beaches
- spits
- barrier beaches/bars
- tombolos
- offshore bars
- sand dunes
- salt marshes
69
What is a beach?
A beach is a depositional landform that stretches from the low tide line to the high tide line and is created when sediment is deposited near the coastline when a wave loses its energy. It is a store in the coastal system.
70
When does beach accretion/excavation occur?
Beach accretion occurs when the beach is being built up by constructive waves, usually during the summer months.
Beach excavation occurs in winter when destructive waves remove sediment from the beach.
71
What is a swash aligned beach?
wave crests approach perpendicular to the coast so there is limited LSD. sediment doesn't travel far along the beach. Wave refraction may reduce the speed of high energy weaves, leading to the formation of a shingle beach with larger sediment.
72
What is a drift aligned beach?
waves approach at a significant angle, so LSD causes the sediment to travel far along the beach, which may lead to the formation of a spit. Generally, larger sediment is found at the start and weather sediment moves further down the beach though LSD, becoming smaller as it does.
73
What are berms?
ridges which mark where the high tide line is at different times of the year, and as a result there may be several berms on a beach characterised by a small ridge or change in sediment type
74
What are cusps?
small curved dips in the beach where the swash comes in, and are slightly lower than the rest of the beach. This creates undulations in the beach profile.
75
What are runnels?
smaller ridges that are often in smooth wet sand further toward the sea, caused by the tides.
76
How do beach profiles vary?
Beach profiles and sediment types vary depending on the distance from the shoreline. Larger sediment is found towards the top of the beach where it has been left after winter storms. The backwash is often weaker than the swash as the water quickly percolates into the sand. As the backwash isn't powerful the larger sediments cannot be moved back down the beach. Scree near the cliffs as a result of weathering and mass movement means that the angle of the beach increases towards the beach.
77
What is a spit?
A long narrow strip of land formed when LSD causes the beach to extend out to sea, usually due to a change in direction of the coastline.
This sediment projection can create a salt marsh due to the sheltered, saline environment where water flow speed is lower, allowing deposition of finer sediment to occur.
78
What does the length of a spit depend upon?
where changing currents or rivers are, which prevents sediment being deposited. This means a spit can never extend across an estuary.
79
How are compound spits formed?
A change in wind/wave direction causes the end of a spit to curve (recurved end). Over time, the spit may be left with multiple recurved tips, which is a compound spit.
In some areas a double spit may occur, where spits form opposite sides of a bay reach out towards each other. If they touch each other, a barrier beach is formed.
80
What are barrier beaches/bars?
A barrier beach occurs when a beach or spit extends across a bay to join two headlands. This traps water behind it leading to the formation of a brackish lagoon which is separated from the sea. Some barrier beaches may have been formed due to rising sea levels after the last glacial period, when meltwater deposited sediment in the coastal zone. If a barrier beach becomes separated from the mainland, it becomes a barrier island.
81
What are tombolos?
A tombolo is a bar or beach that connects the mainland to an offshore island formed due to wave refraction off the coastal island reducing wave velocity, leading to deposition of sediments. They may be covered at high tide.
82
What are offshore bars?
Offshore bars are offshore regions where sand is deposited, as the waves don't have enough energy to carry the sediment to shore. They can be formed when the wave breaks early, instantly depositing its sediment. Waves may pick up sediment from an offshore bar, which then provides an input to the coastal zone. They may also be formed as a result of backwash from destructive waves removing sediment from a beach.
83
What is a vegetation succession?
A vegetation succession is a plant community that changes over time. On coasts where there is a supply of sediment and deposition occurs, pioneer plants begin to grow.
84
How does vegetation stabilise landforms?
- Roots of plants bind soil together reducing erosion
- When submerged, plants provide a protective layer for the ground reducing erosion
- Reduce the wind speed at the surface, reducing erosion
85
What does the formation of sand dunes require?
Sand dunes occur when prevailing winds blow sediment to the back of the beach. This means the formation of sand dunes requires large quantities of sand and a large tidal range, so that the sand is dry enough to be picked up and carried by the wind. Frequent onshore winds are necessary.
86
What is the vegetation succession on a sand dune?
1. Pioneer species such as sea rocket are resistant and able to survive in the salty sand, with its roots helping to bind the dune together.
2. Decaying organic matter adds nutrients and humus to the soil, allowing marram grass to grow
3. Larger plants are able to colonise the area and climatic climax occurs when trees are able to colonise the area.
87
What is the dune succession of a sand dune?
1. Embryo dunes - upper beach area where sand starts to accumulate around a small obstacle (driftwood)
2. Yellow dunes - as more sand accumulates and the dune grows, vegetation may develop on the upper and back dune surfaces, which stabilises the dune. The tallest of the dune succession.
3. Grey dunes - sand develops into soil with lots of moisture and nutrients as vegetation dies, enabling more plant growth
4. Heath and woodland - sandy soils develop as there is greater nutrient content, allowing less brackish plants to survive. Trees will grow with the coastal woodland becoming a natural windbreak to the mainland behind.
88
What is the vegetation succession for a saltmarsh?
1. Algal stage - gut weed and blue green algae establish as they can grow on mud, which their roots bind together
2. Pioneer stage - cordgrass and glasswort grow, their roots begin to stabilise the mud allowing the estuary to grow
3. Establishment stage - salt marsh grass and sea asters grow, creating a carpet of vegetation which increases the height of the marsh
4. Stabilisation - sea thrift, scurvy grass and sea lavender grow, so salt rarely gets submerged beneath the marsh
5. Climax vegetation - rush, sedge, and red fescue grass grow since the salt marsh is only submerged one or two times a year.
89
How do estuarine mudflats and saltmarshes form?
Deposition occurs in river estuaries because when the river waver meets an incoming tide and waves from the sea, the water stops flowing. This means that the water can no longer carry sediment in suspension. They may also occur in sheltered areas such as behind a spit. As most of the sediment is small, you get a build up of mud and over time this can build up to above sea level. Deposition occurs as a result of flocculation. Pioneer plants colonise this area, leading to more sediment becoming trapped. This colonises the transition zone between high and low tide. A meadow is formed as sections of salt marsh rise above the high tide level, leading to climatic climax.
90
How have sea levels changed in the past 20,000 years?
- since 20,000 years ago, sea levels have risen 120 metres
- the increase slowed around 8,000 years ago and levelled off around 3,000 years ago
- since the industrial revolution, sea levels have risen 235mm
- the IPCC predicts that sea levels may rise by 1 metre by 2100
- this could affect aquifers on low lying island atolls such as Kiribati, meaning that the residents no longer have access to fresh water.
- coastal cities may be inundated by tropical storms and tsunamis, so the coastal area may be turned into recreational land as an adaption to climate change
91
What is isostatic sea level change?
Isostatic change occurs when the land rises or falls relative to the sea and is a localised change. It is often the result of isostatic subsidence, as when the glaciers melted the land rebounds in areas that were covered by ice. In the UK, this means that Scotland is rising by 1.5 mm/year, whereas the southeast is subsiding at 1mm/year.
Tectonic activity may cause land subsidence, therefore causing isostatic sea level change.
92
What is eustatic sea level change?
Eustatic change affects the sea level across the whole planet. It is due to thermal expansion or changes in glacial processes. Thermal expansion is the process of water expanding when it gets warmer, rising the sea levels.
93
What are the landforms of emergence?
Where the land has been raised in relation to the coastline, landforms such as arches, stacks, and stumps may be preserved. Raised beaches are common before cliffs which are also raised, with wave cut notches and similar features proof of historic marine erosion.
94
What are landforms of submergence?
Occur when the sea level rises or the coastline sinks in relation to the sea, leading to the formation of rias, fjords, and dalmatian coasts.
95
How are rias formed?
rising sea levels flood narrow winding inlets and river valleys. They are deeper at the mouth of the inlet, with the water depth decreasing further inland.
96
How are fjords formed?
rising sea levels flood deep glacial valleys to create natural inlets and harbours. Fjords are deeper in the middle section than they are at the mouth, with the shallower section identifying where the glacier left the valley.
97
How are dalmatian coasts formed?
valleys running parallel to the coast become flooded as a result of sea level change. This leaves a series of narrow, long and rugged islands, such as in Croatia.
98
What is coastalisation?
Coastalisation is the process by which the coast is being developed and people are moving to the coast, increasing the number of people at risk from marine related environmental activity. It is a result of urbanisation in which people are moving to cities, as the majority of large cities are coastal.
99
What are storm surges?
A storm surge is a result of the low pressure created by large weather events such as tropical storms. It raises the sea level and therefore poses a significant flooding risk.
100
What factors exacerbate the risk of storm surges?
- Removing natural vegetation - mangrove forests are the most productive and complex ecosystem in the world. Mangroves also provide protection against extreme weather events such as cyclones. Many mangrove forests are destroyed to make space for tourism, local industry, or housing. Mangroves are an excellent method of coastal management as they trap sediment leading to accretion on the coastline, helping protect local communities
- Global warming - as the surface of the oceans gets warmer, it is predicted that the frequency and intensity of storms will increase, and so the severity of storm surges and flooding is also expected to increase.
101
What are the consequences of sea level rise for communities?
- Some areas of the coast may have significantly reduced house and land prices leading to economic loss for homeowners and local coastal communities.
- In the UK, many insurers don't provide home insurance to people living along coastlines that are at extreme risk to erosion or storm surges
- Storm surges may damage the environment by destroying plant successions and damaging many coastal landforms. Depositional landforms may be easily destroyed due to their unconsolidated nature. If depositional landforms are removed then erosion may occur more quickly closer to the cliff face, which can increase the risk of collapse of cliffs and threaten land owners.
- Environmental refugees - more than 1 billion people live on coasts that are at risk from coastal flooding and 50% live within 60 km of the coast. As storm surges and erosion along some coastlines are predicted to increase, this will increase the number of displaced people. People may lose their homes, way of life, and culture as they are forced to migrate to avoid the rising sea levels.
102
What is hard engineering?
Hard engineering is a very traditional and somewhat outdated approach to coastal management involving man made structures to prevent erosion. They are often effective at preventing erosion in a desired area, but are high cost and have a significant environmental impact due to the use of concrete. By reducing erosion in one area of the coastline, they may exacerbate erosion elsewhere, therefore their only impact is changing where erosion occurs.
103
What are offshore breakwaters?
Rock barrier which forces waves to break before reaching the shore.
Positives
- Effective at reducing wave energy
Negatives
- Visually unappealing
- Navigation hazard for boats
- Can interfere with LSD
104
What are groynes?
Timber or rock protrusions that trap sediment from LSD.
Positives
- Builds up the beach, protecting the cliff and increasing tourist potential
- Cost effective
Negatives
- Visually unappealing
- Deprives areas downwind of sediment increasing erosion elsewhere
105
What are sea walls?
Concrete structures that absorb and reflect wave energy, with a curved surface.
Positives
- Effective erosion prevention
- Promenade has tourism benefits
Negatives
- Visually unappealing
- Expensive to construct and maintain
- Wave energy elsewhere, with impacts on erosion rates
106
What is rock armour?
Large rocks that reduce wave energy, but allow water to flow through.
Positives
- Cost effective
Negatives
- Rocks are sourced from elsewhere, so do not fit with local lithology
- Pose a hazard if climbed upon
107
What are revetments?
Wooden or concrete ramps that help absorb wave energy.
Positives
- Cost effective
Negatives
- Visually unappealing
- Can need constant maintenance, which creates additional costs.
108
What is cliff regrading and drainage?
Reduces the angle of the cliff to help stabilise it. A steeper cliff will be more likely to collapse.
Positives
- Cost effective
Negatives
- Cliff may collapse suddenly as the cliff is drier leading to rock falls which pose a hazard
- May look unnatural
109
What is dune stabilisation?
Marram grass is planted. The roots help bind the dunes, protecting the land behind.
Positives
- Cost effective
- Creates a wildlife habitat
Negatives
- Planting is time consuming
110
What is marsh creation?
Type of managed retreat allowing low-lying areas to flood.
Positives
- Creates an important wildlife habitat
Negatives
- Farmers lose land and may need compensation as a result
111
What is cost-benefit analysis?
This is an analysis carried out before any form of coastal management takes place. The expected cost of the construction, demolition, maintenance, etc. of a coastal management plan is then compared to the expected benefits of a scheme which may include the value of land, homes, and businesses that will be protected. Cost and benefits may be tangible or intangible. The expected benefits have to outweigh the costs for the project to go ahead.
112
What are sustainable coastal management strategies?
They are holistic strategies, meaning that it is recognised that all of the different sections of the coastline are interlinked and function together as a whole. Smaller sections are not considered separately, unlike in traditional methods.
113
How can you maintain the coast in a sustainable way?
- Managing natural resources like fish to ensure long term productivity
- Educating communities about the need to adapt and how to protect the coastline for future generations
- Monitoring coastal changes and then using adaptation or mitigation as a response to observed changes
- Ensure that everybody is considered when changes are proposed and then adopted
114
What is integrated coastal zone management?
a sustainable coastline management strategy where large sections of coastline are managed with one integrated plan. Management occurs between different political boundaries, which is both beneficial and problematic as decision making is likely to be a longer process.
115
What do Integrated Coastal Zone Management Plans do?
- recognise the importance of the coast for peoples livelihoods
- recognise that coastal management must be sustainable whereby economic development is important, but not prioritised over environmental protection
- must involve all stakeholders, plan for the long term, and try to work with natural processes instead of working against them
- recognise that sediment eroded in one location may form a protective beach elsewhere and therefore a decision to protect one coastal community may not outweigh the disadvantages of exposing another community to increased erosion.
116
What are shoreline management plans?
For each sediment cell in the UK, a SMP has been created to help with coastline management. Each SMP identifies all of the activities which occur within the coastline of each cell. The sediment cells are considered to be closed systems for the purpose of management, although in reality there will be some exchange between cells.
117
What options are considered in a shoreline management plan?
Hold the line, managed retreat, advance the line, no active intervention.
118
What is hold the line?
Defences are used to maintain the current position of the coastline.
119
What is managed retreat?
Defences and engineering techniques are used to allow the coastline to advance inland and create its own natural defences such as salt marshes.
120
What is advance the line?
Defences are built to try and move the shoreline seaward, potentially to protect an important population centre or tourist amenity.
121
What is no active intervention?
The coastline is exposed to natural processes.
122
What factors are considered when choosing a management strategy?
- the economic value of the assets
- the technical feasibility of engineering options
- the ecological and cultural value of the land.
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Why can shoreline management cause conflict?
When considering coastal management there are winners and losers. Winners can be classified as those who benefit economically, environmentally, and socially. Losers can be those who lose their property, job, or who have to relocate elsewhere. Communities and homeowners have a strong attachment to place, so losing their properties and social networks is a great loss.
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What is the location context for Southsea?
Southsea is located on the south of Portsea island, and is within the city of Portsmouth. It has a coastline bordering the Solent between Hampshire and the Isle of Wight. The beach is mostly flint gravel, but some sand is exposed at low tide.
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What is the coastal management scheme at Southsea?
The Southsea Coastal Scheme is the UK's largest local authority-led coastal defences project, worth more than £100M. It will stretch for 4.5km from Old Portsmouth to Eastney, and help to reduce the risk of flooding to more than 10,000 homes and 700 businesses. Phase one of six of the Southsea Coastal Scheme started in September 2020.
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Why does Southsea need new defences?
The current sea defences at Southsea are coming to the end of their lifespan (some dating back to world war two), which increases the risk of flooding. The current defences do not offer a sufficient level of protection, leaving over 8,000 homes and 700 commercial properties at risk from flooding. New defences hope to protect properties along the seafront for the next 100 years.
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What management options have been chosen for Southsea?
- A revetment and a set-back defence has been chosen by public consultation and will offer the standard of protection Southsea requires for the next 100 years, whilst offering an opportunity to enhance the seafront and maintain the areas unique heritage.
- A healthy beach will continue to be maintained where one exists at the moment.
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What is the location context for Happisburgh?
Happisburgh (pronounced Haze-bro) is a settlement on the north Norfolk coast, in England. It has a population of around 1,400 people in 600 houses. Although now a coastal village, this was not always the case. Historical records indicate that over 250 metres of land have been lost between 1600 and 1850. Happisburgh is one of the primary providers of sediment for beaches along the east Norfolk coast, The coastal village is subject to frequent erosion, with houses at risk from falling into the sea.
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What is the geology at happisburgh?
The cliffs at happisburgh range in height from 6 to 10 metres and are composed of a layer-cake sequence of several glacial tills, separated by beds of stratified silt, clay, and sand. The happisburgh till member has a maximum thickness of 3 metres. It is a dark grey, highly consolidated till with a matrix composed of a largely massive clayey sand with rare pebbles of local and far travelled material.
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What causes winter erosion at Happisburgh?
In winter erosion caused by groundwater coupled with increased seasonal storminess causes small-scale frequent, shallow landscaping in the Happisburgh sand member, the Happisburgh sand member is easily eroded and undercutting of the cliff toe reduces the slope stability and cliff failure occurs. The beach surface is low and scouring of the upper surface of the till extends to other till platforms.
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What causes summer erosion at Happisburgh?
In summer the beach surface is higher and covers the winter platform. Wave attack is the dominant form of erosion accompanied by landsliding in the Happisburgh sands.
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What is the Shoreline management plan at Happisburgh?
Managed retreat
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How much did Happisburgh's civil parish shrink by in the 20th century?
Over 0.2 square kilometres by the erosion of its beaches and low cliffs.
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When were groynes constructed at Happisburgh?
1950s
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Why did the rate of erosion at Happisburgh increase rapidly after 1990?
A storm destroyed 300 metres of a wooden revetment.
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What is the Future for Happisburgh?
- it would cost approximately £15 bn to close the gap between the sea defences to the north and south of the village, so this is unlikely.
- the coast is being allowed to erode, meaning communities are being given time to move with some sea defences in place.
- the Norfolk cliffs have been eroding at the present rate for the last 5000 years, so predictions of sea level rise and increased storminess due to climate change are likely to have a profound impact on the coastal erosion at Happisburgh.
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Where is Odisha?
Odisha’s coastal zone is on India’s north-east coast. The coastline borders the Bay of Bengal to the east. The area has huge potential for offshore renewable energy. It is the 8th largest state by area and the 11th largest by population. Its economy is the 16th largest in India.
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How long is Odisha's coast?
480km
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Where is development concentrated in Odisha?
The development in the form of construction and expansion of ports, harbours, tourism, aquaculture, fishing, and other industries are concentrated along the coastal belt. Hazards such as cyclones and floods very often destroy the coast and dampen development activities.
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What is the geology of Odisha?
Unconsolidated, fine material that is easy to erode but very fertile is moved along the coast by longshore drift. Ports being built by river mouths are stopping the flow of sediment, reducing the sediment input for beaches further along the coast. Sediment is deposited by rivers in huge deltas.
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Where is erosion taking place at Odisha?
Deltas are at a lower risk of erosion because sediment is deposited in them, so although there is erosion taking place, the sediment budget is positive overall. The higher risk area is around the Chilika lake sediment plane. A sediment plane is sediment that has been left behind from where a river used to run previously. The worst affected area is at the bottom of a delta that has been dammed upstream, blocking the input of sediment.
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How are deltas formed?
- Deposition of sediment carried by a river
- The greater the flow, the more sediment carried
- As the river slows down, sediment is deposited (heaviest sediments first)
- Deltas occur where the river meets the ocean
- Deltas only occur on flat land
- Monsoon changes the heights of the land slightly which means that new channels are formed.
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How much coastline did Odisha lost to saline ingression between 1990 and 2016?
28%
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What are the effects of erosion in Odisha?
- severe soil erosion has affected the homes of 300 residents in one village
- the locals livelihoods depend on the sea (paddy fields and fishing)
- the water has become too saline to drink so locals have to walk to nearby fishing villages to collect fresh water
- some families refuse to leave ancestral homes
- 10% of the coastline is highly vulnerable to erosion.
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Where is the ICZMP in Odisha?
Gopalpur to Chilika and Paradeep to Dhamara
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When did the ICZMP start?
September 2010
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What organisations funded the ICZMP in Odisha?
World bank and government of Odisha
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How much coast is covered by the ICZMP?
196 km
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What pressures in Odisha face?
The coastal zone is under development pressure induced by population growth and economic activities in the area. It is also experiencing a range of management problems giving rise to increased concern for ecosystems - encroachment, pollution, water resources, siltation, saline ingress, degradation of resources, shoreline erosion, and conflict of interest among stakeholders are some of the problems it faces.
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How has the ICZMP improved the economy of Odisha?
To reduce the dependence of the fishing community on coastal resources and reduce pressure on depleting marine resources, financial assistance has been given to fund alternative livelihoods like dairy, poultry, hygiene dry fish, and value added product preparation. This has been carried out to support people in 72 fishing villages. 600 women in the fishing villages have been able to partake in making baskets out of coconut husks, providing the women exposure to the market-led development processes and improving their mobility. Diversification of the economy builds resilience.
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What has the ICZMP done for tourism?
Tourist amenities have been developed to promote community based ecotourism as a sustainable livelihood. The infrastructure development has led to a 55% rise in employment and income and the number of visitors has increased 31%. To help with ecotourism, 16 boats have been bought to operate at Chilika lake.
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What has the ICZMP done for storm protection?
The coastal districts of Odisha are exposed to regular floods and tropical cyclones. 14 multipurpose cyclone shelters have been constructed to shelter 14,000 people. Normally, the shelters are used as classrooms, vaccination programmes, or social functions.
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How is the ICZMP helping with erosion?
Erosion control measures were adopted for a long term solution to the problem of beach erosion. There were gabions installed to save the most erosion prone 505 metre stretch of coast. People in 56 villages have benefitted from the intervention and 7,000 hectares of highly productive crop fields have been saved from saline ingress.
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How is the ICZMP improving biodiversity?
Mangrove plantation in 300 hectares has enriched the biodiversity and will act as a shelter belt for the area. A crocodile hatchery along with a rearing centre and research lab has been set up, and so has a turtle monitoring centre.
