Coastal Enviroments Flashcards
(170 cards)
1
Q
What is the coast
A
The transition zone between land and the sea
2
Q
What is the coastline
A
The frontier between land and sea
3
Q
What marine processes
A
Processes carried out by the sea
Erosion
Deposition
Transportation
4
Q
What are waves created by
A
Created by winds blowing over the sea , friction sets the waves into motion
5
Q
What can waves do
A
Erode , transport or deposit sediment
6
Q
What is the height of a wave determined by
A
Strength of wind
Length of time wind blows
Fetch ( distance over which wind blows )
7
Q
What does an increase in wave height mean
A
Increase in wave energy
8
Q
What is the main method of transport
A
Long shore drift
9
Q
How does long shore drift occur
A
When waves approach the beach from an angle , prevailing winds determine wave direction .swash follows wave direction and moves material , backwash is perpendicular to coastline due to gravity and moves material backwards into sea. Long shore drift leads to gradual movement of material up the beach
10
Q
What is deposition
A
When the wave loosss energy it drops the sand , rock particles and pebbles it has been carrying . This is called deposition and happens when swash is stronger than backwash ( constructive waves)
11
Q
When is deposition likely to occur
A
when waves enter an area of shallow water
Waves enter a sheltered area e.g cave or bay
There is little wind
There is a good supply of material
12
Q
What are constructive waves
A
Low frequency (6-8 per minute ) Beach gradually develops Low height (<1m) High power swash relative to backwash Long wavelength ( up to 100m) relative to hight
13
Q
What are destructive waves
A
High frequency (10-12 per minute ) High height (>1m) High power backwash relative to swash Sediment forced out to sea Short wavelength (<20m) relative to height
14
Q
What are the 4 processes of marine erosion
A
Hydraulic action
Solution
Abrasion
Attrition
15
Q
Hydraulic action
A
Waves push against cliff and force air into the cracks and prises them apart creating lines of weaknesses
16
Q
Attrition
A
Sea water hurls rocks towards each other . As the rocks collide sharp edges are knocked off over time rocks become smaller smoother and rounder this forms small pebbles and sand
17
Q
Abrasion
A
Rocks scrape against each other wearing them away . Waves pick up stones and hurl them at cliffs wearing the cliff away
18
Q
How does shape of coastline influence erosion
A
Shape of coastline
Headlands of a coastline are exposed to full force of destructive waves whereas bays are more sheltered from waves due to wave refraction. Headlands are therefore eroded quicker because they are hit by the waves with a larger force
19
Q
Weathering influencing erosion
A
Weakens rocks and leaves them susceptible to erosions
20
Q
Wave strength influencing coastline
A
More powerful waves erode more. Only destructive waves erode . If the wave hits the cliff at a high energy level it will have a higher erosive capability.
21
Q
Width of beach affecting erosion
A
A wider beach will absorb more wave energy reducing erosion
22
Q
Human activity affecting erosion
A
Structures built to defend vulnerable coastlines = weakened erosion e.g gabions, rock armour
23
Q
Geology - rock structure affecting coastline
A
How rock strata are aligned in relation to incoming waves
24
Q
Geology rock type influencing erosion
A
Hard rocks are more resistant to erosion e.g chalk and limestone these will be eroded slower and form steep cliffs
Soft rocks lik clays and standstone will be eroded faster and form bays
25
What are sub aerial processes
Coastlines are shaped by wind and rain ( sub aerial processes ) as well as by wave erosion ( marine processes ) . These natural atmospheric processes lead to weathering as well as mass movement
26
Weathering
The break down of rocks caused by freeze thaw and the growth of salt crystals by acid rain and the growth of vegetation roots
27
Mass movement
The removal of cliff gave material under the influence of gravity in the form of rock falls , slumping and landslides
28
How is weathering different To erosion
Weathering is the break down of rock in situ ( one place ) whereas erosion is the wearing away and carrying away of rock by a moving force
29
Physical weathering
Water gets into a crack In a rock and freezes
Water expand as it turns to ice
This is known as freeze thaw weathering and occurs when temperatures rise and fall above and below freezing
As water turns to ice it forces te cracks to widen
The process is most efficient when there is a large temperature difference between night and day
Water contracts as it thaws the ice melts and the rock splits
30
Biological weathering
Plants and animals break down rocks
Seed falls into crack in rock
Seed starts to grow and sends roots into rock
The roots force cracks to widen and the rocks split
31
Chemical weathering
Rain is a weak acid and falls into rocks burning of fossil fuels creates acid rain
The acid slowly eats into rock making it softer limestone is easily dissolved by acid
The rock crumbles at the surface
32
Landforms of erosion
Headlands and bays are the most common
Wave cut platforms
Canes arches stacks and stumps
33
Landforms of deposition
Beaches spits bars and tombolos
34
Where is the Dorset coast
Located on the south coast of England and stretches from Lyme Regis to Bournemouth . It is part of the Jurassic coast
35
What happens in mass movement
Weathered material is forced downslope by mass movement
36
Rapid mass movement example
Slumping - a large area of land moves down a slope and leaves behind a curved surface . Clay contracts and cracks when it rains water runs into cracks and is absorbed until the rock becomes saturated this weakens the tick and it slips down the slope on a slip plane . Slumping is also known as rotational slip
37
Slow mass movement example
Slow mass movements are barely detectable e.g soul creep . Gravity pulls water contained in the soil down a slope . The soil moves downward with water . This increases aftein heavy rainfall . Soil creep leaves overhanging soil and vegetation and ripped terracettes
38
What materials are more susceptible to mass movement
Steepness of the slope and the nature of material on the slope . A slope must be able to contain its own weight to remain stable . Sandstone and shales are more likely to collapse as they consist of loose fitting sediments
Granite and limestone are more likely to sustain their own weight
39
How are caves created
Formed on the side of headlands . Headlands attacked by hydraulic action and abrasion . Faults and joints in the cliff are attached leading to the opening of a cave
40
How is an arch created
The cave is eroded more and enlarged and extends back to the other side of the headland possibly meeting and other cave and forming an arch .
41
How is a stack created
Continued erosion by the sea widens the arch as the sea undercuts pillars of the arch the roof is weakened and eventually collapses leaving a stack separated from the headland . E.g old harry rocks
42
How is a stump created
Further erosion at the bar of the stack causes it to collapse and leave a small flat portion of the original stack as a stump . It may only be visible at low tide
43
What is a wave cut platform
An area at the base of a cliff formed by marine erosion
44
How is a wave cut platform formed
Wave cut notch created by hydraulic action at high tide and low tide
Overtime an overhang is created as the cliff has nothing to support it it will collapse and fall in the sea causing the cliff to retreat
The cliff will retreat until the wave cannot reach the base of it and a wave cut platform will be formed . The sea no longer reaches base of cliff
45
What is a tombolo
A beach which joins and island to a mainland e.g chesil beach which joins the isle of Portland to Dorset mainland . They are spots which have continued to grow seawards until they teach and join an island
46
Tombolo formation
There is a bar of sand and shingle
Prevailing winds cause waves to gradually roll the sand and shingle to the shore . Salt marshes may develop in the calm waters sheltered by the tombolo
47
What is a spit
A landform resulting from marine deposition and longshore drift . It is a long narrow accumulation of sand or shingle with only one end attached to Land , the other end projects out into the sea or across a river estuary e.g Spurn head
48
How is a spit formed
Direction of prevailing winds dicatate wave direction and longshore drift direction
Wave erosion destroys soft boulder clay of the holderness coastline
Longshore drift transports material across the Coastline
Where the coastline changes direction the material carried by LSD is deposited in a line out to sea across a river mouth
Waves are unable to reach the area behind the spit to quiet backwards form
The hooked end of the spit is the result of a Short term change in wind and wave direction
Mud and silt settle creating mud flats and salt marshes in the Humber estuary
On the holderness coastline the spit cannot progress any further due to strong current of river that prevents the spit from progressing further across the estuary
49
How are beaches formed
Accumulation of material deposited when swash is stronger than backwash it is a stretch of shad shingle and pebbles deposited between the high and low water marks along a coast . Created by constructive waves when sediment accumulates more quickly than us carried away . Sediment comes partly from cliff erosion. But mostly from Rivers
50
What is a bar (barrier beach )
E.g slapton sands . Long and narrow and extends across a bay , a lagoon will often form on the landward side of the beach . They are usually formed by the 'rolling a shore ' of a sand or shingle bar by the wave
51
How is a bar formed
Prevailing winds determined wave direction
. A sand or shingle bar is rolled a shore
. A bar of sand is created across the entrance to a shallow bay
A lagoon develops behind the barrier beach in slapton sands it's a freshwater lagoon fed by Rivers
52
What is a storm beach
When waves have more energy during storms and can carry large materials up a beach
53
Why is a coast a system
It is an open system as there are inputs e.g
Wind which causes long shore drift and deposition and outputs materials carried out to sea and sediment deposited above high tide mark
54
What would a cliff made of soft rock look like vs hard rock
Hard - high and steep, cliff face bare rocked rugged , foot of cliff has boulders and role
Soft - lower and less steep , cliff face - smoother evidence of slumping, cliff foot - few rocks some sand and mud
55
How is a beach formed
A beach is a stretch of sand shingle and pebbles deposited between high and low water marks along a coast .formed by constructive waves when wave energy drops they deposit the sand shingle and pebbles they have been carrying . Long shore drift extends the beach . The stronger swash than backwash of the wave means material is moved up the beach
56
Longshore drift wave type
Destructive
57
What happens when waves approach the coast
Friction slows the notion of the wave down creating a crest
58
What do destructive waves do
Plunge material down which then carried away by strong backwash
59
How are landforms of erosion formed on discordant coastline
```
Rock strata is at rights angles to sea . Soft rock (clays and sands ) are eroded faster by hydraulic action forming bays (circular inlets ) e.g studland bay , swanage bay
Hard rocks ( chalk and limestone ) are not eroded as fast and form an outcrop of resistant rock e.g Ballard point durlstom head . Te headland are exposed to waves and erode over time then the whole process starts again
```
60
What do concordant coasts loook like
Rock strata is parallel to sea producing straighter coastlines
61
What caused sea level fall
During the ice age large amounts of water was stored as ice and snow causing sea level fall. This left the old coastline high above sea level . Since the ice age sea levels have risen but not to their precious levels.
62
What does sea level fall reveal
More coastline , beaches are no longer combed by waves An left stranded and exposed above the new lower sea level . These are raised beaches
63
What is an emergent coastline
A coastline asssociated with sea level fall
64
What is a raised beach
An area of sloping ground that sits above present tide line .it is where the sea level used to be . They are covered in shrubs and bushes showing physical inactivity
65
What are relict cliffs
Commonly have wave cut notches , caves arches and stacks . They are behind the raised Beach and were formed due to marine erosion when sea levels were higher. It is a cliff where the souls would previously have been attacking it but is now far from the sea and no longer experiences coastal erosion
66
What is A coastline with a rising sea level
Submergent coastline will have rias and fjords
67
What is aria and how is it formed
A coastal inlet formed by submergence of a lower portion of the river valley .they are drowned river valleys
68
What is a fjord and how's it formed
Deep , narrow elongated sea or lake drain with steep land on 3 sides . Fjords are steeper and deeper variants of rias . They have a shallow mouth as this is where the glacier deposited its sediment . They are particularly found in icy sections of the world . They are drowned glacial valleys
69
Why are coats attractive to humans
Coastal lowlands are attractive to people and their settlements they are some of the most densely populated areas on earth . They offer land agriculture and industry e.g fishing and trading through ports and harbours , tourism.
70
Have have humans changed the coast
Through coastal management to protect coast from extreme erosion or deposition by building sea walls and groynes
71
How is holderness retreating
Worlds most vulnerable coastlines
Looses 2 mil tonnes of material a year as it made of soft boulder clay and string prevailing winds create high levels of longshore drift
72
What happened in mappleton
1992 coastal management scheme coasting 2mil bagan to protect mapleton a village on top of a cliff ok the holderness coastline. Rock armour was placed along the cliff base to prevent erosion and 2 rock groynes were built to prevent longshore drift. But this increased erosion south of mapleton
73
What happens in studland bay
Gets crowded un summer creates fire hazards . Marram grass planted to stabilise sand dunes areas feneced off to reduce access and range to sand dunes from trampling .dunes are equipped with fire Beaters to stop fire hazards
74
What causes sand dune devlopment
Plentiful supply of sand
Strong winds to transport sand
Prevailing winds must be onshore Obstacle to trap sand
Plants are central to formation and growth of dunes
75
How are sand dunes formed
When the beach dries out at low tide some sand is blown to the back of the beach by onshore winds the sand accumulate their due to a small obstacle such as piece of driftwood or dry seaweed . As the accumulation grows an embryo dune is formed . It continues to grow and become more stable . Another dune may develop on the seaward side of the embryo dune. The original dune is now further inland and sheltered from prevailing onshore wind . This sequence continues producing a series of dunes in the form of ridges running parallel to sea
76
What happens to ridges of dunes over time
They become colonised and 'fixed' by vegetation . The older th ridge and further inland the greater the veg cover. The first plants such as sea twitch and couch must be able to cope with
Salinity
Lack of moisture as sand drains quickly
Wind
Temporary submergence by wind blown sand
Once plants become well established environmental conditions improve and other plants begin to apparat eventually dune Heath will become established
77
Discordant coastline
When rock strata is at right angles to sea
78
Concordant coastline
When strata is parralel to sea
79
Lulworth cove formation
South coast of purbeck
Concordant coastline
Large circular inlet of water with steep chalk cliffs at the back . Shallow calm waters and circular shape due to wave refraction
Was once a solid cliff with a stream running to sea
River formed a line of weakness through hard limestone cliffs
Once breached softer purbeck beds , welden beds and greensand eroded rapidly as they were exposed to the river
Overtime softer rocks have been eroded more causing the cove to form
It will not expand as the steep chalk cliffs cannot be eroded
80
Why are cliffs at lulworth cove steeper at the back
Resistant steep chalk cliffs are at the backa me are hard and can maintain their steep shape . The cliffs in th middle are made of clay and are soft and slump as
81
What happens at Swange and studland bay and handfast point
Discordant coastline
East coast of purbeck
Weaker rock erodes faster causing formation of head lands and bays
Headlands are then exposed to waves and erode over time
Then the whole process starts again
82
Coral reef distribution
Most coral reefs are located between the Tropic of Cancer and Capricorn , in the Pacific Ocean , Indian Ocean , Carribean sea , Red Sea and the Persian gulf . Near the equator or where warm currents flow out of tropics such as Florida. Maldives Australia .covers over 284,000km2 of the world
83
What controls coral reef distribution
Temperature - minimum of 18. Grow best between 23-25
Light
Shallow water so the light shines through
Salinity - since coral is a marine creature it can only survive in salt water
Wave action - for well oxygenated salt water
Sediment blocks the corals way of feeding and reduces light
Exposure to air kills coral
84
Social benefits of coral reefs
Provide livelihoods and food to those who live near them . Reef associated fish are a key slice of protein . 1 billion people depend on reef for food and fishing income. People dive swim and enjoy aethestic values of the reef. It's very biodiverse with potential to be used as medicine
85
Ecenomic benefits of coral reef
Fishing
Tourism provides substantial income for those who live near reef. Great Barrier Reef generates well I've 1 biliion$ per year from tourism
86
Environmental
Reefs provide storm protection by reducing wave height and energy . Provides support for mangrove and sea grass habitats by reducing seas energy levels close to shore . Help prevent coastal erosion , flooding and reduces need to build costly coastal defences against flooding and erosion
87
Biodiversity of salt marshes
Abundant herbs , grasses , shrubs , birds , crabs and fish and snails
88
Location Salt marshes
Low energy sheltered conditions protected from waves and storms , between mudflats that are permanently submerged by water and terrestrial vegetation in the intertidal zone . E.g key haven marshes which is protected by hurncastle spit . They survive in saline conditions
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Factors influencing location
Sheltered from open sea e.g at heads of bays and in estuaries because in bays water is salty but in estuaries the water is brackish part salt and part fresh
. They need salinity
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Threats go salt marshes
Reclamation of land to create farmland and sites for industrial and port devlopment
Industrial pollution as many marshes occur in estuaries which are favoured as sites for ports power stations and oil refineries. . Agricultural pollution of water as thy are often near farmland where applications of fertilisers and pesticides leads to europhication
91
Biodiversity mangroves
Nurseries of fish and crustaceans . Rich in wildlife
92
Location mangroves
Tropical coasts with soft soils 30 degrees north and south of the equator . There is a large growth in south east Asia
93
Factor influencing mangrove location
Reef proctects the coast so mangroves can grow and not be eroded by the sea . Mangroves trap sediment from land that would smother sea . They protect against storm surges . That can survive in salty conditions as they have a natural filtration process . They r intertidal . Roots are adapted to filter out salt. Seeds can float and leaves are curled to stop water loss . They Are regularly flooded by the sea
94
Threats mangrove
Clearing as they are perceived as disease ridden. Deforestation trees cut down for timber . Pollution can kill animals and smother mangrove roots killing trees
95
Sand dunes biodiversity
Marram grass lizards
96
Location
Where onshore winds are prevalent and in the intertidal zone e.g studland bay western Isles inner Hebrides
97
Factors influencing location
Wide beach , large quantities of sand , onshore prevailing winds , suitable locations for sand to accumulate , obstacles causes sand accumulation and then marram grass traps sand
98
Threats to sand dunes
Trampling , reduction in sand supply , disturbance leads to loss of vegiatation and blow outs . Near to urban and industrial areas means they are at risk of being built over . In areas of the world trees are planted to stabilise mobile sand dunes
99
ClimAte change threat to Great Barrier Reef
Leads to sea level rise - this is a threat to coral reefs as they can only cope when sea is less than 25 metres deep . Sea levels predicted to rise by 0.68 metres across the Great Barrier Reef by 2100.
Leads to rising temp . Corals temp limit exceeds that are put under thermal stress causing them to expel tiny algae that live within their tissues and provide most of their food and energy. This is coral bleaching and if temp doesn't decrease they starve and die . Sea temp is predicted to rise by 2.5c by 2100
100
Climate change action plan
Established in 2012 by Australian government in order to build reefs health so it can cope with stress and avoid climate change impacts . They are providing strategic and targeted science to support management and adapatation planning to improve outlook of the reef in the face of climate change . They r encouraging action to reduce the extent of climate change by controlling greenhouse gas emissions . Supporting adaptations of reef industries and communities to build reefs resilience
101
Zoning
A loacal solution for improving reefs health and resilience
8 different zones : general use , habitat porotceyiok , conservation park , marine national park , preservation , scientific research , buffer and commonwealth island zone.
102
Zoning results
Fish number and size have increased since implementation . Coral reef is 50% more abundant increased fish population means increased Reef health and resilience
103
Industrial pollution threat local
Pollution poisons coral and leakege of fuels into water and oil spills stop light entering reef killing Coral . Hot water is discharged into sea from power stations increasing water temp
104
How is Industrail pollution managed
Reef water quality protection plan and 'eye on the reef ' where people submit photos of reef to review its health and see pollution affects
105
Human development threat local
Port devlopment leads to dredging of sea floor and creates artificial barriers to freshwater flow . Lots of development for roads and water is located on flood planes and within costal zone this can cause pollution influencing the reef
106
Humans devlopment threat management
Encouraging effort from industry leadership to prevent increasing devlopment near the reef
107
Tourism threat
Careless boating diving and snorkelling results in people touching reefs stirring up sediment collecting coral and dropping anchors and waste on reed
108
Tourism threat management
Permits are given for tourism by Australian government . Permits are required for scuba diving water sports tourist vessels and more . This helps reduce impact on sensitive areas of the reef and encourages responsible behaviour and monitors activities that may become damaging to the reef by asseing its conditions
109
Agricultural run off threat
Increased run off of sediment nutrients and contaminants has lowered water quality and health of the reef . This has led to smothering of coral reef by settling of sediment , reduces light due to murky water .they aren't exposed to light and die . Nitrogen run off from farms leed to algae blooms , they are a prime food for starfish larvae that destroy Coral . Algae also blocks the sun
110
NGO agricultural run off management
WWF are advocating laws to stop farm pollution flowing into reef waters and want government to establish a multi billion dollar fund to help farmers adopt cleaner practices
111
Who uses studland bay
Sunbathers , jetskiiers , rare plant and animal species , dog walkers and nature lovers and families and naturists
112
What's under threat in studland bay
The spiny sea Horse and the dart ford warbler are under threat . The short snorted seahorse lives in studland bays eel grass
113
What harms Eel grass
Boats , several hundred dock there a day and anchors pull up clumps of eel grass.
114
Rare plants
Royal fern and sundew
115
How is studland protected
It's an AONB and contains several site of special scientific interest to protect rare plant and animal species , Unesco world heritage site and a national nature reserve . It's a pressurissed coastline
116
How many visitors are there to studland bay
1 mil per year
| 60% visit in July and august , it's a honey pot site
117
Problems with studland bay tourists
Car pollution and noise
Anchors destroying sea bed
Littering
Oil residue from boats and jet skis pollutes sea water
Fires breaking out from campfires and barbecues
Noise disturbance to rare wildlife
118
Conflict user groups studland bay
Environmental groups - ban boats from docking , replant eel grass , conserve environment reduce tourists
Developers - maximum tourists and tourist activities such as cafes and jet skiing. Not too much litter because unattractive ecenomic lake focusesed
Local residents - frustrated by congestion and pollution
Tourists - increased car park , more recreational amnentites
Fishermen - harbours U polluted water
119
How many people come to studland by car
90%
120
How many boats can visit studland on a summer day
1300
121
How many people depend on studland tourist industry
Over 300
122
Studland oil
Europes largest onshore oil field produces 1500 barrels a day . Key challenge is to find balance between income generation and environmental conservation so the oil plant is camouflaged and noise kept to a mimunum
123
How is studland bay divided
Into zones to stop user conflicts , no boating zones , horse riding zones , kitesurfing zones
124
What is the most costly upkeep of studland bay
Litter disposal and collection
125
How is barbecuing managed studland
Designated zones to stop people barbecuing near sand dunes . Fire beaters are provided . Visitors are educated about important wilditfe and the fragility of the dunes
126
Broad walks studland bay
Encourage people to follow a particular roots where there is no vegutation so they do not trample on the sand dunes . The footpaths are monitored for signs of erosions in the dunes and heathlands
127
How is tourist pressure managed
Acces at only 3 points to concentrate tourist pressure in one area and away from the most environmentally sensitive areas .
128
Where are salt marshes found
In between mudflats and land at mid level often behind a spit or bar as these landforms create a low energy environment
129
How can weather effect salt marshes
Storms can erode the marsh
130
How are salt marshes formed
Low energy waves lint sea erosion so plants can colonise and sediment can accumulate
131
How can climate effect salt marshes
Affects species type , growth rate and sea levels
132
How does salt marsh succession occur
Key haven marshes are located on the south coast of England in southern Hampshire behind hurncastle spit .
The spit provided a sheltered place for sediment to accumulate and for eel grass to accumulate away from the impact of strong winds and coastal erosion
The pioneer colonising plant eel grass helped to stabilise the area by trapping more sediment
Gradually salt resistant plants such as sea blite colonise mudflats they trap more sediment and contribute organic matter when they die , this helps the salt marsh to grow
Eventually salt marsh will grow further and more plants will colonise until the climax community of alder and ash trees is reached with a fully developed creek system . This is known as vegetation succession
133
How does vegutation cope with salt marshes
Glands to secrete salt
| Deeply sunken pores to reduce water loss surface roots to bind the mud . Deep roots to stabilise plant
134
Why is marine erosion a threat to salt marsh
They become exposed on seaward side of the spit and beaches in the spit protected side = exposed slumping platforms of bare mud , if mud is washed away this affects the stability of the spit and destroy mud flats ecosystem
135
What statuses protect keyhaven
Site of special scientific interest
136
Why is a holistic approach needed to save salt marshes
Because spit and marshes are mutually reliant on each other so both need to be considered instead of one or the other
137
What Attempts have been made to protect the spit and salt marshes at keyhaven
559 m rock armour
Nourished with 300 m3 of shingle
Breakwater built at sea to reduce wave energy
100 m rock revetments st eastern end of spit
138
How does increased storm affect sAlt marsh
Greater wave energy may erode marshes and cause flooding
139
Formation of arch
Marine erosion occurred at bottom creating caves . At the top weathering occurs creating cracks . Joints and faults are attacked by hydraulic action
Durdle door
140
Formation of stump
Old harry rocks Weathering e.g freed thaw occurs at top marine erosion occurs at bottom . The arch experiences extreme weathering and crumbles through leaving a stack
141
Wave cut platform formation
E.g. Red end point
Sea erodes base of cliff e.g by hydraulic action at high tide and low tide forming a wave cut notch and an overhang
Overhang is not supported and clippers and a new wave notch forms . Waves no longer reach base and a wave cut platform is left
A wave cut platform is a shallow ledge found at the base of a cliff formed by marine erosion
142
What is A coast
An open system as there are distinct inputs and outputs of matter and energy . When the system is in equilibrium inputs = outputs
If inputs > outputs = positive sediment budget
If outputs >i lotus = negative sediment budget ( a retreating coastline )
Sediment is constantly moving around the uk coastline what happens in one sediment cell will Have a nock on affect on the rest of the coastline.
143
What does coastal management involve
Looking at impacts of management in one area on another
144
What are the major threats to coastlines
Erosion , flooding
Storm surges are the biggest food threat caused by low air pressure that raised height if high tide sea , string onshore winds drive raised sea towards the coast and can breach coastal defences and flood large areas
Tsunamis can also lead to flooding
145
Why is the holderness coast dissapearing
Very exposed waves have a long fetch over the North Sea .
Threatened by sea level rise .
Waves are mainly destructive
Material eroded from cliffs is washed out to sea and moved by lsd the beaches are therefore narrow and do little to protect the coastline ( if beaches were wider waves would break in the beach reducing erosive power ). The coastline is mainly made up of cliffs of soft boulder clay that are easily eroded
146
What are impacts of dissapaerIng holderness coastline
Cliff line retreating greater than 1-2m/year fastest rate in Europe .
Cliff erosion south of mapleton has been accelerated to 10 m/yr. in 1998 main road was 500m from cliff top now in palaces it is only 50
147
Attempts to save holderness coastline
Groynes to trap moving beach material and form protective beach In front of cliff .
Construction of sea walls and revetments at base of cliffs . Tyres and concrete blocks force waves to break offshore .sea wall to protect easington gas station where 25% of nations gas comes through . To reduce erosion in mapleton 2 groynes were constructed to encourage build of beach in front of mapleton by trapping longshore drift
148
Hard engineering
Expensive , short term options of management involve the physical construction of a coastal defence structure . High impact on landscape or environment , less sustainable .
149
Soft engineering
Less expensive works with nature rather than against usually moe long term and sustainable with less impact on environment
150
What is management of coast convenientes with
Erosion and longshore drift
151
Who manages the holderness coast
Under responsibility of DEFRA that supervise schemes carries out by local authorities
152
What is an SMP
Local authorities are encouraged to develop them for their stretch of coast. They provide a detailed assessment of risks associated with coastal processes and set out policies to reduce risks to people and the environment , the basic principle is that natural processes should not be intereferrd with unless necessary to protect life and property
153
What are the 4 possible SMP approaches
2. Do nothing
2. Hold the existing defence line
3. Advance the existing defence line
4. Retreat the existing defence line
154
What is holderness SMO approach
Do nothing in areas that are not currently protects allowing coastal erosion to continue . And hold the line where there are important existing protection works at main settlements
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Where is protected in the holderness coastline
Bridlington / 3.6 km of concrete sea walls with groynes to stabilise beaches
Hornsea with protection of the town and its resort functions by 1.86 km of sea walls groynes and rock armour . Recently height has been added to sea walls to cope with rising sea levels .
Withersea 2.26 km of sea wall groynes and rock armour
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What is the rock back policy
Managed retreat
Local planning guildlines prohibit all building development within 30 m of cliffs edge . Gradual closing down of sights and relocating them more than 400 metres from cliffs eg caravan parks . Anything built between 30/200 metres from cliff edge has to be justified for a need for coastal location
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What are groynes
Wooden barrier built at right angle to the beach. It interrupts water flow and reduces the transportation of material by longshore drift . Made of wood or concrete or stone found in groups at regular intervals along beach
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Advantages and disadvantages of groynes
Adavantage : prevents movement of material along coast through lsd and allows build up of a beach which is a natural defence against erosion as it absorbs energy and attracts tourists
Disadvantage : can be seen as unattractive can be costly to build and maintain many are needed
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What is managed retreat
Areas of the Coast are allowed to erode and flood naturally , normally this will be areas considered low value
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Adavantage and disadvantaged managed retreat
Adavantage : encourages nature to re establish its natural balance with the development of beaches and salt marshes , its cheap and sustainable
Disadvantage : many people need to be compensated for loss of building or farmland people maybe at risk or their homes flooding
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Gabions are ..
Metal cages filled with rocks placed at the foot of cliffs to absorb wave energy
Advantage cheaper than rock armour , absorbs wave energy and allows development of beach can be stacked up and set into cliff to help stabilise it
Disadvantage needs careful construction and constant maintanance expensive wire rusts quickly unless galvanised
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Beach nourishment
Beach material lost through erosion and lsd is replaced with sand and shingle from elsewhere beach size is increased .
Advantages provides a natural looking defence , restores and widens beach for recreational use encourages tourists and works with nature
Disadvantage very expensive requires constant maintenance disruption of beach during nourishment
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Revetments
Wooden slanted or upright blockades parralel to sea on the coast towards back or the beach to protect the cliff or settlement beyond . Most consist of timber slats with rock infill waves break against them and they absorb the energy . Cliff base is protected by beach material held behind barriers
Adavantage protects foot of cliff by absorbing wave energy , easy to construct cheaper tan sea wall does not significantly interface with sediment transportation
Disadvantage ugly , does not completely stop coastal erosion , needs replacing as wood rots
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Rock armour
Large boulders are piled on beach to absorb the energy of waves and encourage build up of beach material , usually made or hard rock that is erosion resistant , absorbs wave energy power and gaps between the rock trap and slow down water lessening erosive ability
Adavantage absorbs wave energy allows build up of beach
Disadvantage expensive to obtain and transport boulders it's ugly
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Cliff regarding and revegitation
Cliffs are cut back to form a more gentle slip to prevent coastal slumping . Drainage pipes are placed in cliff to prevent development of slip planes and remove excess water . Grass and other vegutation growth encouraged as the roots will stabilise cliff
Adavantage works with natural processes prevents cliff collapse vegitation provides new habitat for wildlife
Disadvantage expensive complex engineering needed still requires defences at the bottom of cliff to prevent it being undermined . Some homes on edge of cliff will need to be demolished
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Sea wall
Protects areas from action of tides and waves , it's a buffer between land and sea and reflects wave energy this decreases erosion by destructive waves its effective but costly over time the wall may begin to erode
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How are cliffs formed
Shaped through both erosion and weathering . Soft rock erodes quicker to create gently sloping cliffs hard rock erodes slower to create steep cliffs . A cliff is a steep rock slope usually facing the sea
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Solution
Chemicals in sea dissolve rock
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Non human cycle
Natural cycle
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What is an estuary
River mouth widening into sea where fresh water and sea water mix
