coastal systems + landscape Flashcards
(168 cards)
1
Q
how many system terms are there?
A
8
2
Q
what’s the definition of the system term ‘input’?
A
material or energy moving into the system from outside
3
Q
what’s a coastal example for the system term ‘input’?
A
Precipitation and wind
4
Q
what’s the definition of the system term ‘output’?
A
material or energy moving from the system to the outside
5
Q
what’s a coastal example for the system term ‘output’?
A
ocean currents, rip tides, sediment transfer + evaporation
6
Q
what’s the definition of the system term ‘energy’?
A
power or driving force
7
Q
what’s a coastal example for the system term ‘energy’?
A
energy associated with flowing water, the effects of gravity on cliffs + moving air (wind energy transferred to wave energy)
8
Q
what’s the definition of the system term ‘stores / components ‘?
A
the individual elements or parts of a system
9
Q
what’s a coastal example for the system term ‘stores / components’?
A
beach, sand dunes + nearshore sediment
10
Q
what’s the definition of the system term ‘flows / transfers’?
A
the links or relationships between components
11
Q
what’s a coastal example for the system term ‘flows / transfers’?
A
wind blown sand, mass movement processes + longshore drift
12
Q
what’s the definition of the system term ‘dynamic equilibrium’?
A
a state of balance within a constantly changing system
13
Q
what’s a coastal example of the system term ‘dynamic equilibrium’?
A
constructive + destructive waves. constructive waves build up a beach steeper which encourages destructive waves that plunge rather than surge. destructive waves redistribute sediment offshore which reduces the beach sediment
14
Q
what’s the definition of the system term ‘positive feedback’?
A
where a flow / transfer leads to increase or growth
15
Q
what’s a coastal example of the system term ‘positive feedback’?
A
- Groynes trap sediment, depriving areas further down-drift of beach replenishment + this can exacerbate erosion
- seawalls have the same effect by transferring high energy waves elsewhere along the coast
16
Q
what’s the definition of the system term ‘negative feedback’?
A
where a flow / transfer leads to decrease or decline
17
Q
what’s a coastal example of system term ‘negative feedback’?
A
when the rate of mass movement and weathering exceeds the rate of foot-cliff erosion and a scree slope is formed. over time, this apron of material extends up the cliff face protecting the cliff face from subaerial processes. this leads to a reduction in the effectiveness of weathering and mass movement
18
Q
what are the 2 two feedback mechanisms?
A
- major determinant of what landscape is formed
- as well as geological, climatic + maritime processes
19
Q
describe the term landform?
A
- geomorphic features on the surface of the earth
- ranging from large scale features such as plains, plateaus + mountains to minor features like hills, valleys and alluvial fans
20
Q
describe the term landscape?
A
- part of the earth surface that can be seen from one area
- consists of geographic features / landforms that are characteristics of a particular area
21
Q
how is wave energy formed?
A
- formed by wind
- when there’s a big difference in pressure
22
Q
what are the factors affecting wave energy?
A
- strength of wind
- duration of wind
- the fetch
23
Q
how does wind strength affect wave energy?
A
the strength of wind is determined by the pressure gradient
24
Q
how does the duration of wind affect wave energy?
A
the longer the wind blows, the more powerful waves will become
25
how does the fetch affect wave energy?
the distance of open water over which the wind blows. the longer the fetch, the more powerful the waves
26
how are waves formed?
1- the water becomes shallower + the circular orbit of the water particles changes to an elliptical shape
2- the wavelength + velocity both decrease, and the wave height increases - causing water to back up from behind and rise to a point where it starts to topple over (break)
3- the water rushes up the beach as swash and flows back as backwash
27
what are the 2 wave types?
- destructive
| - constructive
28
what are the characteristics of destructive waves?
- short wavelength
- weak swash
- strong backwash
29
what are the characteristics of constructive waves?
- long wavelength
- strong swash
- weak backwash
30
how is the high tide effect created?
- the moon pulls the ocean towards it creating an outward bulge in the oceans closest to the moon
- directly on the other side of the earth away from the moon creating a high tide effect
31
how is the low tide effect created?
- the water is drained from the other areas of the oceans creating a low tide effect
32
what is the tidal range?
the difference in metres between high and low tide and it's influenced by the position of the moon + sun
33
what tidal range is spring tide?
the highest tidal range
34
what tidal range is neap tide?
the lowest tidal range
35
how are rip currents formed?
- when a series of plunging waves cause a temporary build up of water at the top of the beach
- water tries to return to the sea, but it gets forced below the breaking waves + is very strong
36
where are rip currents usually formed?
they are usually formed between 2 sand banks
37
what are the characteristics of high energy coastlines?
- stretches of Atlantic facing coast
- powerful most of the year
- rate of erosion exceeds the rate of deposition
38
what are the erosional landforms of high energy coastlines?
- headlands
- wave cut platforms
- cliffs
39
what are the characteristics of low energy coastlines?
- waves are less powerful
- coast sheltered from large waves
- rate of disposition exceeds the rate of erosion
40
what is the 5 steps of wave refraction?
1- as waves reach the coastline they are affected by friction caused by the sea bed
2- out in deep water the energy of the wave is identical all the way along as it approaches but it changes as it nears land if the coastline has an irregular shape
3- as the wave nears the land's edge the depth of water decreases, waves get higher + steeper, velocity decreases as friction affects the speed
4- the remaining part of the wave is faster than in front of the headland , so the wave continues with its speed and energy
5- however it's hindered by being dragged slower by the wave affected by the headland and it begins to wrap around the headland and becomes more parallel to the coast
41
what are the 2 types of coastline?
- concordant
| - discordant
42
what is a concordant coastline?
- a 'pacific' or 'concordant' coastline
| - a geological trend is parallel to the coastline
43
what is a discordant coastline?
- 'Atlantic' or 'discordant' coastline
| - geological trend is 90 degrees to coastline
44
what is a sediment cell?
a stretch of coastline usually bordered by two prominent headlands, where the movement of sediment is more or less contained
45
what are the inputs of sediment cells?
inputs are sources and these are primarily derived from the river, coastal erosion and offshore sources such as bars or banks
46
what are the transfers of sediment cells?
the transfers are flows which involve longshore drift together with onshore and offshore processes such as rip currents
47
what are stores of sediment cells?
the stores are sinks which include the beach, sand dunes and offshore deposits (bands and bars)
48
what type of system are sediment cells?
they are often determined by the topography + shape of the coastline which directs the movement of the sediment within the cell, for this reason they are considered to be closed systems
49
what is the role of sediment cells?
sediment is largely recycled within them rather than having significant amounts of new inputs + outputs, the boundaries of the sediment cells tend to be headlands and peninsulas which act as natural barriers to stop the further movement of the sediment
50
what happens to sediment if the wind changes direction?
if the wind changes direction and the movement of the oceans currents also change then it can affect some of the sediment under high-energy conditions and can cause some of the sediment to move off-shore into long term ocean floor stores of sediment. within each of the sediment cells there are smaller sub cells
51
where are some of the sediment cells in the UK?
- St Abb's head
- Flamborough head
- The Wash
- River Thames
- Selsey Bill
- Lands End
52
what are the 6 sources of sediment ?
- glaciers
- wind
- longshore drift
- offshore
- rivers
- cliff erosion
53
how are glaciers a source for sediment ?
the ice blocks hold + carry sediment which is released when ice melts
54
how is wind a source for sediment ?
sand dunes are semi-dynamic as they can be both a sediment source and a sink
55
how is longshore drift a source for sediment ?
sediment is transported from one area (output) to another (input)
56
how is offshore a source for sediment?
bars and banks hold sediment which is moved by waves + storm surges
57
how are rivers a source for sediment ?
an active river has more erosion especially in high rainfall areas. sediment is deposited In the mouth of the river and moved by waves, tides and currents
58
how is cliff erosion a source for sediment?
it's very important in areas of soft / unconsolidated rock eg: Holderness coast and at 10m / year and the southwest has granite so it erodes at a very slow rate
59
what are the 3 main types of weathering?
- physical
- biological
- chemical
60
what is physical weathering?
It occurs when internal pressures are exerted on rock as a result of changes in the physical structure within its mass
61
what is biological weathering?
when living organisms can contribute to the weathering of coastal rocks through the activity of plants + animals
62
what is chemical weathering?
both rain and seawater contain chemicals that can react with chemical compounds in the rock, altering its structure
63
what are some examples of mechanical (physical) weathering?
- frost shattering (freeze thaw)
- salt crystallisation
- wetting and drying
64
how does frost shattering affect weathering?
water enters a crack or joint, as it freezes it expands by 10% exerting pressure on the rock which forces the crack to widen. fragments collect at the base of a cliff as scree which are then used by the sea in costal erosion
65
how does salt crystallisation affect weathering?
salt water from the sea evaporates leaving the salt crystals behind which grow over time adding stresses to the rock, salt can also corrode the rock
66
how does wetting and drying affect weathering?
rocks rich in clay expand as they get wet and contract as they dry leaving the outside layers weak + vulnerable to breaking away. there is a constant cycle of wetting and drying at the coast
67
what are the 3 things that affect chemical weathering?
- carbonation
- oxidation
- solution
68
how does carbonation affect chemical weathering?
rainwater absorbs C02 from the air creating a weak carbonic acid. this reacts with the calcium carbonate in rocks (limestone + chalk) which is easily dissolved. the cooler the temp, more C02 is absorbed so carbonation is more effective in winter
69
how does oxidation affect chemical weathering?
the reaction of rock minerals with O2 leaving rock more susceptible to weathering as it's weaker
70
how does solution affect chemical weathering?
the dissolving of rock minerals
71
what 3 things affect biological weathering?
- plant roots
- animals (marine organisms + birds)
- water
72
how do plant roots affect biological weathering?
the roots grow into small cracks in a cliff face, these cracks widen as the roots grow, which breaks up the rock
73
how do animals affect biological weathering?
birds like puffins + sand martins and animals like rabbits dig burrows into cliffs
74
how does water affect biological weathering?
water running through decays vegetation and it becomes acidic, which leads to increased chemical weathering
75
how is mass movement important to coastal processes?
it works as a sediment source providing sediment to be transported and deposited along the coastline
76
what are the 4 types of mass movement?
- angle of the slope / cliff (gradient)
- rock type + structure (geology)
- vegetation cover
- how wet the ground is (saturation level)
77
what is a soil creep?
- the process operating at a granular scale
- it happens on gentle slopes and is noticeable from the wavy surface it produces
- damp soil moves very slowly down the slope as the weight of water pushes it forwards
- rain splash may release soil grains the fall further downslope
78
what is a mudflow?
- a flow of water that contains large amounts of suspended particles and silt
- it has a higher density + velocity than a streamflow and can deposit only the coarsest part of its load
- this causes irreversible sediment entrainment, its high velocity will not allow it to flow as far as a water flow
79
what is a landslide?
- the movement of a mass of rock, debris or earth down a slope
- its a type of mass wasting which denotes down-slope movement of soil and rock under the direct influence of gravity
80
what is runoff?
- the part of the water cycle that flows over land as surface water instead of being absorbed into groundwater or evaporating
- runoff is that part of the precipitation, snow melt or irrigation water that appears in uncontrolled surface streams, rivers, drains or sewers
81
what is solifluction?
- a common feature of alpine environments throughout the world, characterised by turf-banked, terraces and lobes, freeze-thaw conditions
- when soil is saturated and starts flowing over a slope
82
what is a rockfall?
- when a fragment of rock is detached by sliding, toppling or falling that falls along a vertical or sub-vertical cliff
- it then proceeds down slope by bouncing and flying along ballistic trajectories or by rolling on talus or debris slopes
83
what is a landslip / slump?
- a slump is a form of mass wasting that occurs when a coherent mass of loosely consolidated materials or a rock layer moves a short distance down a slope
- movement is characterised by sliding along a concave - upward or planar surface
84
what is coastal erosion?
- it plays a vital role in there coastal system removing debris from the foot of cliffs and providing sediment sources
- it is created by the energy of the sun, converted by the power of the wind into waves strong enough to change landscapes
- coastal erosional processes tend to work together to erode a stretch of coastline
85
what are the factors affecting coastal erosion?
- waves
- rock type
- geologic structure
- subaerial processes
- presence / absence of a beach
- coastal management
86
how do waves affect coastal erosion?
- the rate and type of erosion experienced on a particular stretch of coast is primarily influenced by the size and type of waves that reach the coast
87
how does the rock type affect coastal erosion?
- rock lithology is important in determining the rate of erosion
- tough + resistant rock e.g. granite erodes at very slow rates compared to weaker clays and shales
88
how does geologic structure affect coastal erosion?
- cracks, joints, bedding planes and faults create weakness in a cliff that can be exploited by erosive processes
- variations in rock type + geological structure can lead to the formation of headlands + bays, as a result of subsequent differential erosion
89
how does subaerial processes affect coastal erosion?
- weathering and mass movement weaken cliffs and create piles of debris that are easily eroded by the sea, increasing the rate of erosion
90
how does the presence or absence of a beach affect coastal erosion?
- beaches absorb wave energy + reduce the impact of waves on a cliff
- if a beach is absent, following excessive erosion or as a result of management techniques elsewhere on the coast, a cliff may experience increased erosion as its more vulnerable to wave attack
91
how does coastal management affect coastal erosion?
- presence of structures such as groynes and sea walls will have impact on sediment transfer + patterns of wave energy along a coastline
- trapping sediment moved by longshore drift, groynes may deprive beaches further down-drift of sediment input + may decrease in extent
- sea walls may deflect wave energy elsewhere along the coast exacerbating erosion in those locations
92
what are the 4 main types of transportation?
- traction
- saltation
- suspension
- solution
93
what is traction?
traction is rolling sediment along the seabed because its too heavy to pick up
94
what is saltation?
sediment is bounced along the seabed, light enough to be picked up / dislodged but too heavy to stay suspended
95
what is suspension?
smaller, lighter sediment is carried within the flow of the water
96
what is solution?
dissolved load - chemicals dissolved in the water and transported elsewhere
97
describe the 4 steps of longshore drift?
1- swash carries sediment up the beach at an angle (same as prevailing winds)
2- as wave advances, material is carried up the beach at an angle
3- backwash pulls material down the beach at right angles to the shore due to gravity
4- creates a zigzag movement
98
what are the 2 coastal depositions?
- marine deposition
| - aeolian deposition
99
what is marine deposition?
when sediment carried by seawater is deposited
100
what is aeolian deposition?
when sediment carried by the wind is deposited
101
what are the 7 marine processes?
- hydraulic action
- wave quarrying
- corrasion
- abrasion
- cavitation
- solution
- attrition
102
what is hydraulic action?
- the sheer power of the waves as they smash against the cliff
- air becomes trapped in the cracks in the rock and causes the rock to break apart
103
what is wave quarrying?
- erosion happens the high energy, tall waves hit the cliff face
- they have the power to enlarge joints + remove large chunks of rock in one go through vibration
- this occurs due to the intense force of these waves
104
what is corrasion?
- when rock caught up in serving waves are hurled at a cliff face causing it to be chipped + gauged
- wearing away of the river bed and banks by the load hitting against them
105
what is abrasion?
- when the waves picks up sediment and throws these load items against a rock
- the repeated impact chips away at the rock face until small fragments break away
- most effective in high energy destructive waves with a large wave height and it throws items with greater force , resulting in faster rates of erosion by abrasion
106
what is attrition?
- where material is transported by a wave and is eroded through collision with other load items
- it breaks down sediment into smaller sized particles and the repeated collision blunts any of the particles sharp edges, making the sediment increasingly rounded
107
what is cavitation?
- a form of hydraulic action and is caused by compression of air in sea-facing joints as waves crash against cliffs it can cause sea water to be severely compressed
- as the wave recedes the pressure reduces + air comes out of solution in violent 'fizzing' enlarging fissures within joints
- air bubbles trapped in the water get compressed into small spaces like cracks' in river banks
108
what is solution (corrosion)?
- occurs when weak carbonic acid in seawater dissolves rock at the coastline and breaks it down
- also when sediment that has dissolved completely will be transported in solution
- minerals that are dissolved in the water are carried along in solution, this typically occurs in areas where the underlying bed rock is limestone
109
how is a wave cut platform formed?
1- wave notch is created at / near the high tide level (by hydraulic action + corrosion)
2- notch increases in size + undercuts the cliff
3- rock above becomes unstable + collapses
4- cliff retreats inland leaving a gently sloping wave cut platform
110
what are ridges and runnels ?
- series of ridges and troughs running parallel to the coast near the low water mark
- the ridges are formed by deposition during backwash and the runnels are formed when water runs back to the ocean
111
what are cusps?
- semicircular shaped depressions with coarser material around the edge and finer material in the middle
- formed by the waves reaching the same point and backwash scouring out the finer material in the centre
112
what are ripples?
- relatively small, elongated ridges that form on the beach
| - waves and currents flow across loose sand which is dragged along the bottom and is piled up
113
what are berms?
- a series of small ridges that form near the high tide mark
- deposited by the swash of constructive waves
114
what is a storm beach?
- a ridge found near the back of the beach composed of larger sediment
- deposited by waves during storm events
115
what are depositional landforms?
- deposition occurs when the sediment and is dropped due to a loss of energy, often caused by friction or turbulence
116
what are the 7 landforms created by deposition?
- beaches
- spits
- tombolos
- offshore bars
- barrier beaches
- barrier islands
- sand dunes
117
what are the inputs of beaches?
- beach nourishment
- cliff + dune erosion
- fluvial sediment
- longshore transport
- onshore transport (swash)
118
what are the output of beaches?
- offshore transport (backwash)
- sand mining
- longshore transport
- offshore wind transport
- storm events (quarrying)
119
when is a swash aligned beach formed?
they form when waves break parallel to the coast
120
when is a drift aligned beach formed?
they form when longshore drift moves material along the coast
121
what are the characteristics of a swash aligned beach?
- low energy environment such as bays
- waves arrive parallel to the shore
- beach consists of either sand or shingle (dependant on sediment + wave power)
122
what are the characteristics of a drift aligned beach?
- waves approach coast at an angle
- longshore drift moves sediment along the beach
- often resulting in spits (sediment sink or store)
- sediment maybe graded along the beach
- finer shingle carried further along the beach and becoming more rounded as they move
123
what are spits?
- a long, narrow finger of sand or shingle jutting out into the sea from the land
- it forms on coasts where there is significant longshore drift
- spits form on drift aligned beaches, sand or shingle is moved along the coast by longshore drift
- as wave refraction carries material round into the more sheltered water behind the spit, this is known as recurved tip
124
what is a tombolo?
- a beach that has formed between a small island and the mainland
- deposition occurs where waves lose their energy and the tombolo begins to build up
- they may be covered at high tide
125
what are offshore bars?
- aka sandbars, offshore bars are submerged ridges of sand or coarse sediment created
- destructive waves erode sand and deposit it offshore
- offshore bars act as sediment sinks + sediment input stores
- they can absorb wave energy reducing the impact of waves in the coastline
126
what are barrier beaches?
- where a beach extends across a bay to form 2 headlands e.g. start bay, slapton Devon
- barrier beaches and bars can also trap water behind them to form lagoons
127
what's a sand dune?
- small ridges to hills of sand found at the top of a beach, above the usual maximum reach of the waves
128
what are psammosere?
- an ecological succession that began life on newly exposed coastal sand
- most common psammosere are sand dune systems
129
what is climax vegetation?
- the dominant mix of vegetation species that characterise an environment
- given time to occur and reach stability
130
what is plant succession?
- a directional change in the types of plant species that occupy a given area through time
- it involves the process of colonisation, establishment and extinction
131
where do sand dunes develop?
- largely sandy beaches
- large tidal zones exposing a large beach
- shallow beach gradient providing good conditions for sediment transport
- persistent onshore winds to dry and move the sand particles by saltation inland
132
what happens to the beach at low tide?
- the sand dries out allowing the prevailing winds to move the loose sand up the beach
- most moves by saltation in a series of short hops but strong winds may be powerful enough to carry the finer sand grains for longer distances
133
what are embryo dunes?
- sand begins to accumulate when it meets an obstruction on the beach
- seaweed, dead seabirds, driftwood and other detritus may all serve this purpose
- these embryo dunes may disappear as quickly as they form but some may eventually be colonised by plants + the sand stabilised
- conditions are very extreme, with high pH values (over 8), rapid drainage, no humus, high wind speed and lots of salt spray
- won't reach higher than 1m
134
what are foredunes?
- the first plants to colonise foredunes are lyme grass, sea couch grass and marram grass
- these plants are drought resistant + capable of with standing burial by the shifting sand
- as they grow up through the sand, they help trap more sand so the dunes increase in height
- they can reach unto 5m
135
what are yellow dunes?
- they begin to show greater diversity of plants as conditions become more favourable
- as plants die + decay a humus layer builds up and this traps both water + nutrients
- the pH is now only slightly alkaline (7.5), there is more shelter and less salt spray
- the dunes by this stage may well have reached 5-10m
- up to 80% of the sand surface may now be vegetated
136
what are grey dunes?
- they are much more stable + mosses and lichens fill the few remaining spaces between plants so that vegetation cover may reach 100%
- small shrubs (brambles, gorse, blackthorn) appear for the first time
- environmental conditions 50-100m from the sea are much more friendly. there is shelter from the harshest winds, humus is beginning to darken the surface layers and a true soil begins to form
- they are 10m in height and wider than dunes nearer shore
137
what is dune slack?
- are found between the more mature dunes where the water table reaches the surface causing seasonal or even permanent water logging and surface water
- plants which are well adapted to these damp, sheltered hollows include rushes, edges, cotton grass + creeping willow
138
what are mature dunes?
- they are found several 100m from the shore
- left undisturbed these dunes develop a soil which can support shrubs + trees including hawthorn, ash and birch
- humans may plant fast-growing conifers which flourish in sandy soil
- an oak climax vegetation may develop
139
what are salt marshes?
- halosere environments (tolerant to salty conditions)
- a tidal landform consisting of silt + mud
- coastal ecosystems in the upper coastal intertidal zone between land + open salt water
- they protect shorelines from erosion by buffering wave action
- complex plant succession categorised by wetland species such as reeds and rushes
140
what conditions are required for salt marshes to form?
- sheltered river estuaries, behind spits
- where wave energy is low + there is fine sediment available
- where there are inter-tidal mudflats
- where the processes of flocculation occur
141
what are the human threats to salt marshes?
- industrial pollution harms many marsh species, oil pollution in the solent has contributed to the decline of spartina
- agricultural pollution has led to eutrophication + the disruption of the marsh + marine ecosystems
- dredging removes sediment and this may reduce mudflat accumulation it also affects tidal + other currents that may have an impact on scour and erosion
142
what are the natural threats to salt marshes?
- sea levels may rise too quickly for marshes to adjust , increased incidence of storms lead to increased flooding
- storms create greater wave energy + more potential erosion and may lead to a loss of sediment supply
- changing temp + rainfall patterns may affect the tolerance of the marsh species
143
describe global climate change and sea level rises
- the relative levels of land and oceans are continually changing
- they happen at different time scales - from daily tidal cycles to changes in the oceans volume due to glacial + interglacial cycles that occur over millions of years
144
what are the glacial + interglacial periods?
- during the quaternary period there were alternating cold (glacial) periods where the sea level fell
- and several warm (interglacial) periods where the sea levels rose
145
what is eustatic change?
- global changes in sea level
- sea level rises or falls
- precipitation falls as snow and huge ice sheets are created. ice sheets store / hold the water so sea levels drop
- as temp rises, ice sheets melt and retreat. the stored water returns to the rivers and the sea level rises
146
what is isostatic change?
- local changes in sea level
- the land rises or falls relative to the sea
- the weight of the ice sheets causes land to sink (isostatic subsidence)
- as the ice sheets melt, the weight lessens and so the land readjusts (isostatic recovery)
147
describe isostatic change in the UK?
- land in the north and west is still rising as a result of isostatic recovery. it is along these coastlines that features of falling sea level are most evident
- land in the south and east is sinking. rivers pour water + sediment into the Thames estuary and the English Channel. the weight of this sediment causes the crust to sink + relative sea level rise
- south-east England faces increased flood risk as a result to isostatic change
148
what is tectonic level change?
- past tectonic activity has had a direct impact on some coasts across the world, as well as on sea levels
- this is due to an uplift of mountain ranges + coastal land at destructive and collision plate margins that resulted in a relative fall in sea level in some parts of the world
- local tilting of land at destructive e.g. some ancient Mediterranean ports have been submerged and others have been stranded above the current sea level
149
what are the 2 emergent features on a coastline?
- raised beaches
| - wave cut platform
150
what are raised beaches and how are they formed?
- raised beaches are platforms formed out of coastal erosion
- while sea level remains the same, land that was once at sea level is eroded. this leaves the adjacent land further above sea level
151
what is a wave cut platform and how are they formed?
- a wide gently sloping surface found at the foot of a cliff
- the sea attacks the base of the cliff between high and low water mark
- a wave cut notch is formed by erosional processes such as abrasion + hydraulic action
152
what are the 3 submegent features on a coastline?
- rias
- fjords
- Dalmatians
153
what are rias and how are they formed?
- a drowned river valley which makes it much wider than would be expected based on the river flowing into it
- a funnel shaped estuary that occurs at a river mouth and is formed by the submergence of the lower portion of the river valley
- generally occur along a rugged coast perpendicular to a mountain chain
154
what are fjords and how are they formed?
- a long, deep narrow body of water that reaches far inland
- often set in a U-shaped valley with steep walls of rock on either side
- they are mainly found in Norway, Chile, New Zealand, Canada and Greenland
- formed by glaciers
155
what is a Dalmatian coastline and how are they formed?
- formed where the geology creates valleys parallel to the coast so that when sea level rises, a series of elongated islands remain offshore
- they are found in Croatia
156
what is hard engineering?
- the building of entirely artificial structures using various materials such as rock, concrete and steel to reduce or stop the impacts of coastal processes
157
what are the 5 types of hard engineering?
- groynes
- sea wall
- rip rap
- revetment
- offshore break water
158
describe how groynes prevent erosion and the positive / negatives of them
- they are wooden fences / walls made from piles of rock built out into the sea
- advantage = prevents longshore drift moving beach material along the coast
- disadvantage = unattractive, costly to build + maintain
159
describe how sea walls prevent erosion and the positive/ negatives of them
- concrete barrier along the coast which absorbs the energy of the waves
- advantage = effective, creates promenades
- disadvantage = causes erosion offshore, expensive, ugly
160
describe how rip rap prevent erosion and the positive/ negatives of them
- made from granite / hard rock, placed at the base of the cliff to absorb energy
- advantage = cheap, east to construct, recreational
- disadvantage = dangerous, eye sore if rocks aren't local
161
describe how revetment prevent erosion and the positive/ negatives of them
- sloping concrete or wooden defence facing the sea, traps beach material
- advantage = cheap
- disadvantage = ugly, lots of maintenance
162
describe how off shore break water prevent erosion and the positive/ negatives of them
- built parallel to the coast, off the coast from rock + waves are forced to break before shore
- advantage = doesn't obstruct beach
- disadvantage = ugly, navigation hazard
163
what is soft engineering?
- a softer, more environmentally friendly approach often uses natural material and tries to work with natural processes
164
what are the 4 types of soft engineering?
- beach replenishment
- management retreat
- cliff regrading
- dune stabilisation
165
describe how beach replenishment prevents erosion and the positive/ negatives of them
- sand is replaced along the beach
- advantages = effective at dispersing the energy of the waves
- disadvantage = expensive, must be done continuously + disrupts marine life
166
describe how management retreat prevents erosion and the positive/ negatives of them
- allows the coast to take back the land by removing existing sea defences
- advantages = habitats form, natural sea defence, cheap
- disadvantage = conflict, land will erode and flood
167
describe how cliff regrading prevents erosion and the positive/ negatives of them
- reducing the angle of a cliff to stabilise it. drainage removes excess water to prevent landslide
- advantage = cheap, effective on clay / loose rock
- disadvantage = drainage can dry it out too much, homes on cliff may be demolished
168
describe how dune stabilisation prevent erosion and the positive/ negatives of them
- planting marram grass + fencing of areas protect dunes from erosion
- advantage = cheap + sustainable, provide habitats, maintain natural coast environment
- disadvantage = time consuming, may be eroded if people ignore signs
