Physical- Coast Flashcards
(232 cards)
0
Q
Give 4 examples of inputs into the system?
A
- Sediment from river
- Wave energy
- Storm
- Tides
1
Q
What is a coast?
A
A coast is a narrow piece of land where the sea and the lap overlap. It is an example of an open system as there are inputs and outputs of both energy and matter.
2
Q
Give 4 processes of coasts…
A
- Deposition
- Erosion
- Transportation
- Longshore drift
3
Q
Name several outputs…
A
Beach Sand dunes Caves Cliffs Salt marshes
4
Q
What is the wave length?
A
The distance between 2 crests
5
Q
What is a crest?
A
The peak of the wave
6
Q
What is the wave height?
A
The distance between the crest and the trough
7
Q
What is a trough?
A
The bottom of the wave
8
Q
What is the wave period?
A
The time taken for a wave to travel through one wave length
9
Q
What is the steepness?
A
The height/ Length
10
Q
How does a wave form?
A
- In deep water, the water ‘bobs’ up and down
- wind on the surface causes frictional drag producing motion on the upper surface of the water
- Only when the wave breaks across land is water moved inland
11
Q
What effects the size of the wave?
A
The amount of wind
12
Q
What is the fetch?
A
The distance a wave travels. The greater the fetch the larger the wave
13
Q
What are the 3 factors affecting the size of the wave?
A
Fetch
Wind
Time
14
Q
Why does the South West of the UK have large waves?
A
- It has a large fetch as the sea is uninterrupted by land
- Prevailing wind
15
Q
What is the swash?
A
The movement of water up the beach. The angle is determined by the direction of the wind
16
Q
What is the backwash?
A
The movement of water down the beach. It is always at a right angle to the beach because of gravity.
17
Q
What are the features of a constructive wave?
A
Strong swash, weak backwash, deposits material, shallow material
18
Q
What are the features of a destructive wave?
A
Weak swash, strong backwash, erodes material, steep beach and deep water
20
Q
What is a coast?
A
Narrow piece of land where the land and sea meet.
21
Q
What is the coast an example of?
A
An open system
22
Q
Give an example of the coast as an open system?
A
Input of wave energy results in erosion which results in the output of a cave
23
Q
Name 4 inputs
A
Sediment from rivers
Wave energy
Storm
Tides
24
Q
Name 4 processes
A
Erosion
Deposition
Transportation
Longshore drift
25
Name 6 outputs
```
Beach
Sand dune
Cave
Cliff
Salt marshes
Sediment (weathering and mass movement)
```
26
What is wave length?
The distance between 2 crests (m)
27
What is wave height?
Distance between crest and trough (m)
28
What is the wave period?
Time for wave to travel through one length (secs)
29
How is a wave formed?
In deep water, it bobs up and down.
Wind on the surface causes frictional drag producing motion on the surface.
The greater the wind the greater the wave.
When wave breaks across land the water is moved on land.
30
What is the fetch?
The distance a wave travels before breaking. The greater the fetch, the greater the wave.
31
How does time affect the size of the wave?
Longer the wind blows the bigger the wave/
32
Why does the South West UK have large waves?
Large fetch as sea is uninterrupted
| Prevailing wind
33
What is the swash?
The movement of water up the beach. The angle of water is determined by the direction of the wind.
34
What is the backwash?
The movement of water down the beach. The water is always at right angles to the beach because of gravity.
35
What is swell?
Waves formed by distant storms and that travel long distances.
36
What are the 3 things which affect the size of a wave?
Fetch
Wind
Time
37
What determines whether a wave will erode or deposit?
Steepness
38
What is the steepness of a wave?
Height/length
39
How are constructive waves formed?
From swell and a large fetch
40
Describe the wave length of a constructive wave
Large wave length, and therefore a long wave period.
41
Where do constructive waves occur?
Beaches with a low angle.
42
What happens as constructive waves break?
Although they have a strong swash, because they have to cross a wide area it is soon dissipated leaving only a weak backwash.
43
When do destructive waves occur?
When the fetch is short
44
What are destructive waves like?
Steep and high
45
What is the wave length of a destructive wave like?
It has a small wave length in relation to wave height resulting in a shorter wave period.
46
When do destructive waves break?
Away from shore and due to their steepness are high in energy.
47
Where are destructive waves likely to occur? What does this mean?
Beaches with a steeper angle, therefore their energy is very concentrated in a small area.
48
What happens to material?
Some material may be thrown up by the large waves, but most is carried downwards by the strong backwash. As material is constantly carried downwards, the beach becomes gentler in its lower section.
49
What will happen if wave power is strong for a significant part of the year?
More erosion
50
What effect will strong winds have?
Waves will stronger resulting in more erosion.
51
What will happen in the Northern Hemisphere on a HEC on the West
Prevailing wind resulting in stronger waves and more erosion on the West coast.
52
What will happen in sheltered seas e.g. the Baltic
Less wind resulting in less erosion
53
What will happen in an area dominated by high pressure?
Not much wind, weak waves results in more deposition
54
What will happen in the Southern Hemisphere on a HEC on the East?
More windy resulting in stronger waves and more erosion on the East coast
55
What will happen if there is a long fetch?
Waves travel long distances, and become more powerful resulting in erosion.
56
What will happen in low pressure systems?
Strong winds resulting in more erosion.
57
What is a sediment cell?
A closed system, where no sediment is transferred from one cell to another.
58
How many sediment cells are there in the UK?
11
59
What is wave refraction?
The bending of waves due to the shape of the land.
60
What happens to waves in deeper water?
They move forward, meanwhile waves in shallow water are restricted by frictional drag so the waves bend.
61
What happens as the waves near the headland?
It drags in the shallow water near the headland, which decreases the wave length making them taller and steeper like destructive waves, which cause more erosion.
62
What happens as waves near the bay?
In deeper water so travel faster giving a longer wavelength, shallower waves like constructive which results in more deposition.
63
Where does sediment come from?
Rivers entering the sea
Cliffs
Transported up the coast by Longshore drift
64
What are tides?
Rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the earth
65
What is the spring tide?
When the moon and sun are in alignment
66
What is the neap tides?
When the moon and sun are at right angles
67
What are the features of a spring tide?
Maximum tidal range
High waters higher than average and low waters lower than average
Stronger currents than normal
68
What are the features of neap tides?
Tidal range is at its minimum.
Gravitational pull is less strong, leading to lowest high tides and highest low tides
Less extreme tidal conditions
69
What is another factor affecting the tides?
The geomorphology of the sea basins
70
What is the Coriolis effect?
The earths rotation deflects objects towards the equator causing a tidal bulge there.
71
What are the 4 processes of erosion?
Hydraulic pressure
Solution
Attrition
Abrasion
72
What is attrition?
Is material carried by the waves which bump into each other and are smoothed and broken down into smaller particles.
73
What is hydraulic action?
The force of water against the coast. Waves enter cracks (faults) in the coastline and compress the air within. When the wave retreats, the air in the crack expands quickly causing a minor explosion
74
What is solution?
Chemical action of sea water. The acids in the salt water slowly dissolves rocks e.g. limestone and chalk
75
What is abrasion?
Is the process where the coast is worn down by material arrived by the waves.
76
Name the 7 factors which affect the rate of erosion?
```
Geology
Where the waves break
Wave type
Steepness of beach
Type of beach
Fetch
Shore of coastline
```
77
How does geology affect the rate of erosion?
Marine erosion occurs more rapidly where rocks are weaker. The dip of the rock strata can have an impact depending on whether the bed is vertical, horizontal or dipped.
78
How does where the wave breaks affect the rate of erosion?
Waves which break at the foot of the cliff are likely to cause the most erosion
Waves which break earlier on the beach dissipate most of their energy before they reach the cliff.
79
How does the wave type affect the rate of erosion?
Steeper, high energy waves have more energy, so erode material more easily.
Shallow waves carry much less energy, so erosion happens at a much slower rate.
80
How does the steepness of the beach affect the rate of erosion?
Steep beaches give way to deeper beaches offshore, allowing waves to approach unimpeded. This permits steeper waves, which erode more material.
Shallow beaches act as a buffer causing drag, meaning only shallow, low energy waves can form.
81
How does the beach type affect the rate of erosion?
Pebble beaches allow infiltration, leading to less water and therefore a weaker backwash. This results in more sediment being moved up the beach than down it.
Sandy beaches allow the opposite.
82
How does the fetch affect the rate of erosion?
Longer fetch allows a greater build up of energy meaning high energy waves which erode more quickly.
Opposite for short fetch.
83
What are the 3 types of sub- aerial weathering?
Physical weathering
Biological weathering
Chemical weathering
84
What must happen for mass movement to occur?
The underlying rock must be weakened by sub-aerial weathering.
85
What are the two types of physical weathering?
Freeze thaw
| Pressure release
86
What happens in the freeze thaw process of physical weathering?
Water enters racks in the rocks and repeatedly freezes and melts. When it freezes it expands by up to 9%. Repeated fluctuations weaken rock with fragments breaking off.
87
What happens in the pressure release process of physical weathering?
When pressure is removed from the top of a jointed rock, expansion occurs and further opens the cracks.
88
What happens in biological weathering?
Weathering resulting from organic agents such as tree roots growing or animals burrowing into joints.
89
What happens in chemical weathering?
Either the...
Alternate wetting and drying of rock, which weakens it over time or the dissolving rock in sea water and accelerated weathering of rock by acid rain.
90
What is the name of the building in Scarborough which was swept away by a landslide?
Holbeck hall
91
What cause the landslide in Scarborough to occur?
Walkers, bikers and horses contribute to soil erosion on the cliff edge.
Weight of building added pressure to cliff edge increasing instability.
Saturated soil from heavy rainfall- soil creep.
92
What happened in Scarborough?
Land slip began on 3rd June 2003 to the 5th when parts of the hotel fell into the sea.
The owners tried to sue Scarborough council but lost.
93
What is soil creep?
The soil moving very slowly, about 1cm a year.
94
How can soil creep happen?
1) Rainfall causes particles to move down stream.
2) During a wet period, soil particles expand and move down hill due to gravity when they dry.
3) Freeze-thaw- water expansion heaves particles up at right angles, while thawing particles fall downhill under gravity.
95
What is solifluction?
Occurs in tundra areas where soils are frozen for at least 9 months of the year and vegetation is sparse. Topsoil thaws briefly in summer months, the additional water and lack of vegetation binding the soil together which leads to an active flowing layer.
96
What is earthflow?
Moves at around 5 to 15Km per year and on steeper slopes of 5 to 15 degrees. The movement occurs where the ground has become saturated, producing bulging lobes of soil.
97
What is mudflow?
Faster than soil creep or earthflow at 1Km per hour, Produce bulging lobes of soil but occur on unconsolidated land after very heavy rainfall,
98
What are slides and slumps?
Slides maintain their structure and move as a large mass. Slumps can appear to have a rotational element producing a curved ruptured surface. Cliffs formed of weak or impermeable rock like clay are particularly susceptible to this after prolonged rainfall.
99
What is rockfall?
Rapid movement of rock, where slopes exceed 40 degrees. Result from chemical or physical weathering which produce debris slopes beneath the cliff as material from the rockfall disintegrates at the cliff foot.
100
What is runoff?
Moves fine materials like silt and clay particles down slopes, especially where there is a continuous flow of water or little vegetation to anchor particles or impede runoff.
101
Give an example of soil creep?
Sheep pastures, Dorset, UK
102
Give an example of earthflow and mudflow?
California coast
103
Give an example of rockfall?
St Helier, September 2013, Jersey
104
Give an example of slides+ slumps?
Thredbo, Australia, 18 died in landslide
105
What is solution?
Minerals are dissolved in sea water and carried in solution. The load is not visible and can come from chalk or limestone and calcium carbonate.
106
What is suspension?
Small particles e.g. silts and clays are picked up by the currents, especially during storms when strong winds generate high energy waves.
107
What is saltation?
Small pieces of shingle or large grains of sand are bounced along the sea bed. Currents cannot keep the larger and heavier sediment afloat for long periods.
108
What is traction?
Pebbles and larger sediment are rolled and dragged along the sea bed.
109
What is longshore drift?
Waves and currents moving countless tonnes of material up and down shores along the coast.
110
How does longshore drift occur?
It occurs through the process of erosion and deposition and results in a deficit of sediment in one area and a surplus in another, which can create new land masses.
111
When does the sea deposit material?
Barrier
Not much energy
Sediment carried
112
What is coastal deposition?
Occurs when the accumulation of sand and shingle exceeds its depletion. Takes place in sheltered areas with low energy waves or where rapid coastal erosion further along the coast supplies an abundant amount of material.
113
How are headlands and bays formed?
1) Bays are formed due to rapid erosion of less resistant soft rocks such as clay.
2) Headlands are left sticking out as rocky outcrops as the hard rock e.g. chalk as resisted erosion.
3) Bays are sheltered by headlands so less erosion happens here.
4) Meanwhile, the headland is left vulnerable to erosion and the waves energy is concentrated here.
114
How is a wave cut platform formed?
1) Base of cliff - hydraulic action, abrasion, solution - undercutting of cliff leaving a wave-cut notch.
2) Top of cliff - sub-aerial weathering - biological weathering - chemical weathering.
3) Cliff weakens - overhang eventually collapses.
4) Process repeated and as the cliff retreats, at the foot of it is left a shallow sloped beach. This is wave-cut platform.
115
What is a geo?
When erosion excavates enough material along a vertical joint or plane of weakness, forming a narrow steep sided inlet e.g. the Shetland Islands
116
What is a blow hole?
1) Abrasion and hydraulic action exploit weaknesses in the cliff.
2) If erosion continues horizontally, a sea cave is formed and then a natural arch.
3) However, if it continues vertically a blow hole or gloup is formed.
117
What are the erosional processes on a headland?
1) Large cracks due to hydraulic action.
2) Crack grows into a cave through hydraulic action and abrasion.
3) Cave becomes larger.
4) The cave breaks through the headland forming a natural arch.
5) The arch is eroded and collapses.
6) This leaves a tall rock stack.
7) The stack is eroded forming a stump.
118
What is a sand dune?
Found in association with the landforms of coastal deposition- bars, spits. e.g. Sefton coast (longest continuous belt of sand dunes in Britain)
119
How is a sand dune formed?
1) Requires frequent and strong offshore winds.
2) Needs a wide foreshore exposed at low tide, so there is more chance of the sand drying out, and leaving time for onshore winds to carry the sand inland beyond the mean high tide mark.
3) Requires the presence of a trap for the blown sand to encourage accumulation. This trap can be shingle, tufts of grass, or drifted debris dumped by waves in a storm.
120
Explain the sand dune succession?
The evolution of plant communities at a site over time from pioneer species to climax vegetation...
- At each stage of the succession the plant community alters the soil and microclimate, allowing the establishment of another group of species.
- One community of plants is therefore replaced by another as the succession develops.
- Eventually, a climax community is reached where the vegetation is in a state of equilibrium with the environment and there is no further influx of new species.
121
What could cause deposition?
1) Weak wind
2) High pressure systems
3) Shallow water
122
What is a spit?
Spits are long ridges of sand and shingle which are attached to land at one end (proximal end) and finishes in the open sea (distal end).
123
What are the different sand dunes?
1) Embryo
2) Fore
3) Yellow
4) Grey
5) Dune slack
6) Mature
124
What are the conditions on the embryo dune?
1m in height and have a PH value above 8. There is rapid drainage, no humus and lots of salt spray + high winds.
125
What is humus?
Decayed material
126
What are the conditions on the fore dune?
First plants begin to colonise including Lyme grass and Marram grass which has an extensive root system which helps to bind the sand together.
They are drought resistant and as they grow up through the sand they help trap sand to increase the dunes in height-5m
Other pioneering plants include sea rocket and saltwort.
127
What are the conditions on the yellow dune?
More variety of plants causes a layer of humus to accumulate.
Soil is now around 7.5 PH.
More shelter and less spray.
Marram still dominates but other plants may include creeping fescue, mosses, lichens, sea holly and sea spurge.
Dunes 5-10m in height.
80% vegetated
Animal droppings enrich soil.
128
What are the conditions on the grey dune?
More stable and mosses and lichens fill spaces so cover may be 100%.
Marram grass is less common
Red fescue, sand sedge and sea spurge start to dominate.
Small shrubs like brambles and buckthorn appear.
50-100m from sea
Acid soil
10m in height.
129
What are dune slacks?
Water table reaches surface causing surface water. Plants include sedges, cotton grass and creeping willow.
A peaty soil may develop.
130
What are the conditions at mature dunes?
Several hundred m from shore
Support shrubs and trees such as ash and birch.
Eventually, an oak climax vegetation may develop.
131
Describe the formation of a spit?
1) Material is carried eastwards by longshore drift.
2) The orientation of the old coastline changes, and some larger shingle pebbles are deposited in the slacker water.
3) As the spit continues to grow, storm waves throw larger material above the high water mark making the feature more permanent.
4) Fine sand is carried towards the end of the spit
5) Many spits develop a hooked end. This may be because a change in the prevailing wind coincides with the second-most-dominant wave direction and the second largest fetch.
132
Give a named example of an unstable spit?
Spurns Head
133
Why has Spurns Head developed?
- Natural position for the formation of a spit at the Northern side of the Humber estuary.
- Longshore drift is particularly heavy because of rapid rates of erosion along the 60km of Boulder clay cliffs at the Holderness Coast.
- Dominant wind direction is NE, this helps keep alignment parallel to the coast and the distal end in the Humber estuary.
134
Why is Spurn Head unstable?
- 8Km long
- Narrow points vulnerable to storm waves.
- Breaches throughout history
- After a breach spit reforms due to favourable conditions
135
How was Spurn Head protected?
- Between 1850 and 1950, the policy was to protect it. A concrete wall was built designed to stop erosion and wooden groynes were intended to trap and hold sand in place.
- However, Spurn Head needs to move for its survival and now the wall has collapsed in places and the groynes are in disrepair.
136
What has protecting Spurns head caused?
- Narrow sections are vulnerable to erosion from Northerly Gales because the spit is now in the wrong place. Its position has remained stationary while the Holderness coast has retreated.
137
What is a bar?
A bar extends across the mouth of a bay, sometimes reaching the other side and sealing off its entrance.
138
What is Scolt head island
An offshore bar which forms a ridge of shingle and sand and has a westward facing spit growing out from its westward edge. Its northern side is lined with sand dunes.
139
How is a bar formed?
1) Occur in highly sheltered coastal environments where any streams flowing into the bay are small and have weak flows allowing deposition.
2) Sediment accumulation exceeds removal rates.
3) Follows the same formation of a spit.
140
What are favourable conditions for the formation of spits and bars?
1) Bend or change in the direction of the coastline
2) Plentiful load
3) Active longshore drift
4) Environment favouring constructive waves.
141
What is the first step in the formation of salt marshes?
- In a sheltered river estuary or behind a spit vegetation begins to grow on intertidal mudflats which will colonise the mud and silts.
- Eel grass and Spartina grow here
142
What is the second step in the formation of salt marshes?
- Spartina is the dominant vegetation on tidal flats as it grows all year round. Its root system can grow 2m into sediment slowing tidal flow and trapping more mud and silt.
- 15cm high- sea lavender, red fescue and sea thrift.
143
What is the third step in the formation of salt marshes?
- Additional build up of sediment and dead organic matter mean the marsh can grow upward at 25cm per year.
- The irregular profile of the marshes creates creeks which enable the tide to come in and out. Salt pans may be formed when hollows are cut off and trapped sea water evaporates. Eventually, the marsh rises above sea level leading to new types of vegetation.
- Reeds and rushes
- Ash and oak
144
What are ridges and runnels?
- The spreading out of waves energy across a wide area of beach tends to cause ridges and intervening depressions called runnels.
- They are common in shallow sandy beaches.
145
What are berms?
- Small ridges that develop at the position of the mean high tide mark resulting from deposition at the top of the swash.
- Berms are generally created by smaller waves with less energy, so the material tends to be smaller.
146
What are beach cusps?
- Semi- circular depressions.
- They are smaller temporary features formed by a collection of waves reaching the same point.
- The sides of the cusp, channel the incoming swash into the centre.
147
What are 3 features of beaches?
1) Ridges and runnels
2) Berms
3) Beach cusps
148
What is the case study for a depositional feature?
Key Haven, Saltmarshes
149
Give some general information about the Key Haven Salt marshes...
- South Hampshire- South Coast
- Formed behind Hurst Castle Spit
- Spit protects marsh from strong wind and erosion
- Has reached climax community
150
What are the human threats to Key Haven Saltmarshes?
1) Construction of groynes starves the spit which shelters the marsh.
2) Sediment is removed on people's shoes and bags as tourism increases.
151
What are the physical threats to Key Haven saltmarshes?
1) Marsh is retreating up to 6m a year.
2) Sea level rise and storms
3) Animals grazing destabilises sediment.
152
What are the human impacts of the threat to Key Haven saltmarshes?
1) Existing coastal flood defences depend on the saltmarshes for defence.
2) Damage to tourism and commercial activities.
3) Increased wave exposure has affected the number and position of yacht moorings and safety within marine recreation areas.
153
What are the physical impacts of the threat to Key Haven saltmarshes?
1) As a saltmarsh erodes benefits may include the creation of a mudflat which provide excellent feeding grounds for winter birds.
2) Unprotected shoreline would be vulnerable to erosion and risk of flooding would increase.
154
What are the management strategies put in place in 1996 to protect the Key Haven saltmarshes?
1) SMP added 300,000 m3 of shingle to the spit and 550m of rock armour.
2) SSSI and part of a nature reserve
3) 'Hard engineering' don't provide cost-effective solutions which are environmentally acceptable.
4) Inter-tidal recharge: raising area between high and low water with imported sediment- encourages deposition- experimental, unproven
155
What is eustatic change?
World wide changes in sea level caused by glacial and interglacial periods. During a glacial period water is stored on the land and sea levels fall. During inter-glacial periods sea levels rise as ice melts.
156
Give three examples of landforms of submergence (Eustatic change)...
1) Ria
2) Estuary
3) Fjord
157
What is isostatic change?
Localised and relative change in sea level caused by the crusts response to loading and unloading of ice. Isostatic recovery is greatest over Scotland because that was where most of the ice was. The land in Scotland is rising approximately 4 to 20mm per year, whereas the land in the South is sinking.
158
What is an example of an emergent landform?
1) Raised beaches
159
What are emergent landforms associated with?
A drop in sea level.
160
How would sea level rise impact on the UK?
- Land below 5m at risk e.g Suffolk
- Salt water polluting fresh water.
- Defences needed to be provided or re-built.
161
How would sea level rise impact on Bangladesh?
- 1m sea level rise would result in nearly 20% of the country underwater
- 13 million people displaced
- Protection would cost $1 billion.
162
What are the key features of a ria?
- Gentle sloping valley sides
- Wide- 1Km either side
- 50m high
163
How is a ria formed?
1) During the ice age, rivers which continued to flow cut their valleys down to the lower base level.
2) When the ice melted and the sea level rose, the lower parts of the main valley and its tributaries were drowned to produce sheltered, winding inlets called rias.
164
What are the key features of a fjord?
- U-shaped valley
- Steep cliff like sides
- Can be 1000m deep
- Shallow at sea end known as the threshold
- Straight plan view
165
How is a fjord formed?
1) Located where glaciers are able to erode below sea-level.
2) When the ice melted, valleys were flooded by the rising sea to form long, deep, narrow inlets with precipitous sides and hanging valleys: fjords are drowned glacial troughs.
166
Give an example of a fjord...
Norway
167
Give an example of a Ria?
Sydney
168
How is a fjard formed?
1) Rocky low inlets of land which have been previously glaciated and have now been drowned.
2) Although they can be deep like fjords, they are usually more irregular in shape.
169
Give an example of a fjard?
Strangford Lough, Northern Ireland
170
How are raised beaches formed?
1) As the land rose, former wave cut platforms and their beaches were raised above the rest of the waves.
2) They are recognised by a line of degraded cliffs fronted by what was originally a wave cut platform. Within the old cliff line there may be relic landforms such as wave cut notches, arches or stocks.These are evidence of the marine erosion which occurred when the sea level was with the coastline.
171
Give a named example of a raised beach?
Kings Cave, Isle of Aran
172
What has been the sequence of sea level change?
1) Formation of glaciers and ice sheets. Eustatic fall in sea level gives rise to a negative change in base level.
2) Continued growth of ice sheets. Isostatic depression of land under the ice produces a positive change in base level.
3) Ice sheets begin to melt. Eustatic rise in sea-level with a positive change in base level.
4) Continued decline of ice sheets and glaciers. Isostatic uplift of the land under former ice sheets results in a negative change in base level.
173
What is isostatic change?
A local change in sea level resulting from the depression of the earths crust by increased/decreased weight imposed upon it by a growing or declining ice sheet.
174
What is eustatic change?
Refers to a worldwide fall/use in sea level due to changes in the hydrological cycle caused by water being held in storage on land in ice sheets.
175
What is orogeny?
Tectonic plates especially at collision and destructive plate margins have resulted in the uplift of new mountain ranges.
176
What is epeirogeny?
Local tilting of the land.
177
What is base level?
The lowest level to which erosion by running water can take place.
178
What does a positive change in base level mean?
The sea level has risen in relation to the land
179
Give 4 methods of soft-engineering?
1) Beach Nourishment
2) Cliff re-grading
3) Sand dunes
4) Salt marshes
180
What is beach nourishment?
- The addition of new sand to beaches
181
What are the advantages of beach nourishment?
- Slows coastal erosion.
182
What are the disadvantages of beach nourishment?
- Sand must be of the same grain size/ consistency otherwise the process of erosion will increase.
- Addition of new sand may complicate nesting for turtles.
- $12.5 million every 6 years- $535 per m
183
What is cliff re-grading?
- Humans decrease the gradient of the cliff in order to decrease the chances of mass movement or cliff collapse.
e. g. Holderness coast
184
What are the advantages of cliff re-grading?
- Cheap
- Low-cost maintenance
- Aesthetically pleasing
185
What are the disadvantages of cliff re-grading?
- Doesn't stop erosion
| - Can disrupt habitats
186
How are sand dunes used to stop erosion?
- Established vegetation will prevent erosion and will accelerate natural recovery after storm damage creating a reservoir of sand within the foredunes that will make the dunes better able to withstand the next period of erosion.
e. g. Sefton Coast
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What are the advantages of sand dunes as soft-engineering?
- Dune replanting stabilises and replenishes the dunes.
- Low cost
- Priority habitat- Natterjack toad
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What are the disadvantages of sand dunes in soft engineering?
- Labour intensive
| - On- going managment
189
How are salt marshes used to prevent erosion?
- Absorbs water to prevent flooding and take away the impact of destructive waves.
e. g. Key Haven Marshes- SSSI, wetland of international importance.
190
What are the advantages of using salt marshes to prevent erosion?
- Protect an extended area of coastline which would otherwise be exposed to wave attack and flooding.
191
What are the disadvantages of salt marshes in preventing erosion?
- Vulnerable to marine erosion
| - Could affect the stability of the spit which would reduce primary productivity.
192
What is soft engineering?
Holistic approach which works alongside nature.
193
What are the general advantages of soft engineering?
- Cheaper
- Less environmental impact
- Long term and sustainable
194
What are the general disadvantages of soft engineering?
- Management of natural, dynamic features is far more complicated
- Some areas of coastline will be left unprotected or not as well protected.
195
What are the advantages of the beach nourishment at Miami beach?
- Nourishment restores and widens recreational space.
- Structures behind beach are protected as long as the added sand remains.
- As erosion continues, beach nourishment doesn't leave hazards on the beach or in the surf zone. Big advantage compared with 'hard' beach stabilisation e.g seawalls
196
What are the disadvantages of Miami beach?
- Beach nourishment erodes 2 or 3 times faster than normal sand.
- Expensive- must be repeated
- Construction zone during nourishment
- Damage, destroy or hurt marine and beach life
- Different sized grain-particles affect the way waves interact with the beach.
- Cost of saving beach property through shoreline is usually greater than the value of the property to be saved.
197
Where is Miami Beach?
Florida
198
Give some facts about Miami beach?
- 21 million tourists per year
- 100,000 truck loads of sand
- 726m of beach
- 272,000 people live in storm surge area.
199
What are some general advantages of hard engineering?
- Actually prevents flooding
- Development of infrastructure in places which wouldn't have been viable before.
- Provide tourist destinations
- Alternate habitats
200
Give some facts about the Cardiff Bay Barrage?
- 1.1Km long
- 2nd largest tidal range in world
- 1994
- Re-generated unused docklands
201
What is a curved seawall?
- Solid concrete structure acts as an obstruction to waves.
202
What are the advantages of curved seawalls?
- Curve dissipates wave energy
| - Can withstand severe waves
203
What are the disadvantages of curved seawalls?
- Very high cost and maintenance
| - Potential for overflowing, flanking and undermining of wall
204
What is revetment?
- Slatted fence angled into the sea
| - Includes gabions which are steel cages filled with large pebbles
205
What are the advantages of revetment?
- Very good at dissipating wave energy
| - Cheap structural option
206
What are the disadvantages of revetment?
- Not as strong as sea walls
| - Liable to damage during high wave activity
207
What are groynes?
- Timber planks attached to piles driven into the beach
208
What are the advantages of groynes?
- Cheaper option
- Less visual impact
- Accumulating sediment builds attractive beach
209
What are the disadvantages of groynes?
- Shorter lifespan than stone or concrete
| - Causes sediment starvation and prevents LD.
210
What is rip rap?
- Large blocks of hard igneous rock piled up at the base of a cliff
211
What are the advantages of rip rap?
- Dissipates wave energy effectively
| - Low capital cost and no maintenance cost
212
What are the disadvantages of rip rap?
- Blocks must be heavy enough to resist movement
- Sourced from Norway
- Creates hazardous gaps
213
What can lead to coastal flooding?
1) Severe weather conditions
2) Large waves
3) High tide levels
4) Combination of storm surge and river flooding
5) Seasonal heating and cooling
214
How do severe weather conditions contribute to coastal floods?
- Create meteorological conditions that increase water level, creating a storm surge.
- Conditions include strong winds and low atmospheric pressure that can be caused by tropical cyclones or other severe weather conditions.
215
How do large waves contribute to coastal flooding?
- Arise from local winds or swell from distant storms
| - Raise average coastal water levels and can cause large and damaging waves to reach land.
216
How do high tide levels contribute to coastal flooding?
- Caused by normal variations in the astronomical tide cycle.
- When a severe storm hits during high tide, the risk of flooding increases.
217
How can a combination of storm surges and river flooding cause coastal flooding?
- Increases flood severity
218
How does seasonal heating and cooling contribute to coastal flooding?
- Contribute to high water levels
219
What is a storm surge?
- An abnormal rise of water generated by a storm, over and above the predicted astronomical tides or wave conditions.
220
How can humans worsen coastal flooding?
- Overtopping of a barrier
| - Breaking of a barrier
221
What happened in 1953 in Convey Island (Essex)?
Coastal flooding
222
What were the causes of the 1953 coastal flooding?
- Tidal surge
- High spring tide
- Natural depression
- Defences failed
223
What were the consequences of coastal flooding?
- 300 dead
- 40,000 homeless
- 160,000 acres flooded
224
What are the general consequences of coastal flooding?
- Over 50% of the world population lives within a coastal zone.
- Habitats like dunes and marshes destroyed.
- Houses and businesses at risk
- Lakes damaged due to saltwater intrusion.
- Decline in tourism
- Loss of biodiversity or even extinction
225
What are the possible management strategies of coastal flooding?
1) Do nothing- eventual abandonment
2) Managed retreat
3) Hold the line- hard engineering
4) Move seaward- new defences in front of old ones
5) Limited intervention- adjustments to cope with gradual inundation.
226
What happened in 2008?
Cyclone Nargis
227
What were the short-term causes of cyclone nargis?
- Low pressure system developed into a tropical depression and became a cyclone on the 28th April.
- 150mph
- 3.6m storm surge
- 600m rain fell
228
What were the long-term causes of coastal flooding for cyclone nargis
- Large areas of land no higher than 10m above sea level.
- Unprotected coastline
- Fragile housing
229
What were the short-term effects of cyclone nargis?
- 100,000 dead
- 50,000 missing
- 3 million homeless
- 3/4 livestock dead
- $4 billion
- 75% hospitals and 50% schools destroyed.
- flooding 50Km inland.
230
What were the long term effects of cyclone nargis?
- Land and crops destroyed- 70% of population works in agriculture
231
What were the short term responses of cyclone nargis?
- Meteorological agencies warned Burmese government but they failed to issue any warnings
- Government refused to accept international aid for a month and confiscated aid from poor to provide its military.
- After 2 weeks only 25% had received aid.
- $190 million given in aid.
232
What are the long term responses of cyclone nargis?
- Three year relief and recovery operation targeted 13 towns run by the red cross
- Delta used to house 7/53 million people now very poor.
- National Disaster Preparedness Central committee (NDPCC) issued a programme for reconstruction and implemented plans for future disasters.
