2.B - Case studies of high energy and low energy coastlines Flashcards
(137 cards)
1
Q
what do geology and marine processes determine?
A
the morphology of the coastline
2
Q
what type of coastline is the yorkshire coast?
A
- discordant
- at the southern end, there is a large chalk headland
- then there are sandstones, shales and limestones.
- meaning that there are bands of harder and softer rock, lending themselves to the formation of bays/headlands
3
Q
at what pace does shale erode?
A
0.8 metres/year
4
Q
at what pace does chalk/limestone erode?
A
- harder rocks
- only erode at 0.1m/year
5
Q
significance of geology at yorkshire coast
A
- geology will be a long term and permanent factor influencing the landscape that will determine the rate at which marine processes can occur.
6
Q
how is wave energy influenced by wind at yorkshire coastline?
A
- the winds blow from the north meaning that there is a large fetch of 1500km , as a result the waves have a high energy therefore are mostly destructive
- longshore drift moves sediment from north to south
7
Q
how does wind and wave energy vary on the yorkshire coast?
A
- the winds and therefore the wave energy will vary from day to day (diurnally)
- and from summer to winter (seasonally).
- most days the wave energy will not be very strong and there will be relatively low levels of erosion and therefore change to the landforms, but then storms could bring very high levels of energy, causing rapid change in short periods of time, mostly the winter.
8
Q
where is sediment supplied from at the Yorkshire coast?
A
- as sea levels rose during the last ice age, material was moved onshore (in the same manner as a barrier beach). clearly this input is historic and is no longer happening, therefore sediment being removed will not be getting replaced by this.
- erosion of chalk, sandstone, shale and limestone cliffs. this is ongoing, the rate of input depending upon geology and wave strength.
- the river Esk deposits sediment (but due to it being a heavily managed river, this is minimal).
9
Q
how does sediment accumulation vary across the Yorkshire coastline?
A
- the rate of sediment movement varies across the coastline
- there are bays with areas of sediment accumulation and cliffs where there is no sediment accumulation
10
Q
LANDFORMS - saltburn to Flamborough head
A
high wave energy along a 60km long coastline in yorkshire
11
Q
LANDFORMS - geology of the yorkshire coast
A
mainly of sandstone, shales and limestones formed during the jurassic period as well as some Carboniferous
12
Q
LANDFORMS - yorkshire coast fetch
A
the dominant waves affecting this coastline are from the N and NW with the distance of open sea greater than 1500km
13
Q
LANDFORMS - erosion rates at yorkshire coast
A
the rates vary along the coast from 0.8m/yr shale and clay to 0.1m/yr sandstone and limestone
14
Q
LANDFORMS - flamborough head
A
- large chalk headland.
- the cliffs have till on top, a superficial deposit left behind by glaciers during the Devensian glacial period
15
Q
LANDFORMS - sediment sources at yorkshire coast
A
- nearshore - driven onshore as sea levels rose at the end of the last glacial period
- cliff erosion - sandstone and chalk, boulder clay and gravel
- river esk enters at Whitby - this supplies only limited sediment
16
Q
LANDFORMS - cliffs at flamborough
A
- made of chalk, which is physically strong,
- the cliffs are high 20-30m and vertical.
- however the top of the cliffs (composed of till) are lowered by mass movement to an angle of about 40 degrees
17
Q
LANDFORMS - cliffs at robin hood’s bay and saltburn
A
- stepped profile due to more varied geology
- steeper areas - sandstone and limestone
18
Q
LANDFORMS - shore platform at robin hood’s bay
A
- typical angle of 1 degree and maximum width of 500m
- formed within the last 6000 yrs
- relict feature
19
Q
LANDFORMS - filey bay
A
- eroded into weak Kimmeridge clay
- more resistant limestone and chalk either side forming the headlands
20
Q
LANDFORMS - beach at saltburn
A
- it has a net increase of sediment of 9245m3 between 2008 and 2011.
- a rare example along this coastline as the waves ususally erode sediment before accumulation can take place
21
Q
LANDFORMS - green stack pinnacle
A
- as a result of wave refraction, the wave energy becomes very concentrated on Flamborough Head
- this has left a stack isolated at the end where hydraulic action has opened up a joint in the chalk
22
Q
LANDFORMS - robin hood’s bay
A
- eroded into lower lias shales.
- with stronger bands of sandstone to the north (ness point) and south (ravenscar), forming the 2 headlands
23
Q
what are the key features of flamborough head?
A
- large chalk headland
- the cliffs have till on top, a superficial deposit left behind glaciers during the Devensian glacial period
24
Q
what is till?
A
a superficial deposit left behind by glaciers during the Devensian glacial period
25
what are the key features of the **cliffs at flamborough**?
- made of chalk, which is physically strong
- the cliffs are high 20-30m and vertical
- however the *top* of the cliffs (composed of till) are lowered by **mass movement** to an angle of about 40 degrees
26
how will the **cliffs at Flamborough** change over time?
- lower part is strong rock with tightly bonded material
- slow to erode via marine processes
- cliff collapse is most likely in stormy weather
- the upper half of the cliff which is weaker will see a lot more biological weathering and mass movement (slumping/slipping) more regularly
- erosion here will happen more extensively in the winter compared to the summer
27
what are the key features of the **cliffs at Robin Hood's Bay and Saltburn**?
- stepped profile due to more varied geology
- steeper areas = sandstone and limestones
28
how will the **cliffs at Robin Hood's Bay and Saltburn** change over time?
- there are horizontal bedding planes here with stronger rocks interspersed by weaker rocks
- the weaker rocks will be subject to more weathering and erosion therefore slumping is more common, making the angle of cliff not as steep
- these will retreat more quickly than the Flamborough Head cliffs
- erosion here will happen more extensively in the winter compared to the summer
29
what are the key features of the **shore platform at Robin Hood's Bay**?
- typical angle of 1 degree and maximum width of 500m
- formation of the platform (formed within the last 6000 yrs and relict feature)
30
how will the **shore platform at Robin Hood's Bay** change over time?
- probably formed over the last 600 years, but as a shore platform grows, it acts as its own breakwater
- therefore waves will erode the shore notch, making the platform bigger at a slower rate
- as a result, this shore platform **will not be growing quickly,** unless sea level rise means that the waves can reach the base of the cliffs more regularly
31
what are the key features of **Filey Bay**?
- eroded into weak Kimmeridge clay
- more resistant limestone and chalk either side, forming the headlands
32
how will **Filey Bay** change over time?
- the bay will be accumulating sediment during summer constructive wave periods
- but will be losing sediment in winter months due to winter storms and destructive waves
- a dynamic equilibrium will exist, which will keep the beach roughly the same size
33
what are the key features of the **beach at saltburn**?
- it has a net increase of sediment of **9245 m3** between 2008 and 2011
- a rare example along this coastline as the waves usually erode sediment before accretion (accumulation) can take place
- it will be losing sediment in winter months due to winter storms and destructive waves
34
how will the **beach at Saltburn** change over time?
- it has a net increase of sediment of **9245 m3** between 2008 and 2011
- it will be losing sediment in winter months due to winter storms and destructive waves
35
what are the key features of the **green stacks pinnacle**?
- as a result of wave refraction, the wave energy becomes very concentrated on Flamborough Head
- this has left a stack isolated at the end where hydraulic action has opened up a joint in the chalk
36
how will the **green stacks pinnacle** change over time?
- over time, a stack will collapse to form a stump
- most likely during a winter storm after years of erosion
37
what are the key features of the **arch at selwick bay**?
- next to green stacks pinnacle, there is an arch
38
how will the **arch at selwick bay** change over time?
arch will eventually collapse to form a stack
39
what are the key features of **Robin Hood's bay**?
- eroded into lower lias shales
- with stronger bands of sandstone to the north (Ness Point) and south (Ravenscar), forming the 2 headlands
40
how will the **Robin Hood's bay** change over time?
- the bay will be accumulating sediment during summer constructive wave periods, but will be losing sediment in winter months and destructive waves
- a dynamic equilibrium will exist which will keep the beach roughly the same size
41
how is **geology** (main 2 rock types chalk/limestone and lias) and **stacks/stumps** (e.g. Flamborough Head/Green Stacks) interrelated?
- discordant coastlines create layers of hard and soft rocks
- this means that headlands stick out (harder rock).
- over time, these can be eroded by high energy waves refracting and creating stacks and stumps
- e.g. Green Stack at Flamborough Head or Selwick Bay?
42
how are **wave energy** and **bays** (e.g. Fiely Bay/Selwicks Bay) interrelated?
- waves become divergent in Filey Bay
- reducing wave energy
- increasing deposition rates
43
how are **headlands** and **bays** (e.g. Fiely Bay/Selwicks Bay) interrelated?
- wave energy is focused on headlands like Filey Brigg
- Filey Brigg Headland absorbs destructive wave energy reaching Filey Bay (due to wave refraction. waves slow down ∴ low energy in bay ∴ deposition)
- therefore there is less destructive waves = ↑ deposition = biggest bay (wave refraction)
44
how are **cliffs** (Flamborough Head/Ness point) and **wave energy** interrelated?
- the headland at Filey brigg will act as a focal point for wave energy
- which causes waves to refract
45
how are **cliffs** (Flamborough Head/Ness point) and **bays** (e.g. Fiely Bay/Selwicks Bay) interrelated?
- cliff erosion provides main source of sediment
- Lias eroding at a rate of 0.8m/y provides sediment source
46
what rate do lias erode at?
Lias eroding at a rate of 0.8m/y provides sediment source
47
what are lias?
a blue-grey clayey limestone derived from marl deposited in the Lower Jurassic, found chiefly in south-western England.
48
how are **cliffs** (Flamborough Head/Ness point) and **shore platforms** interrelated?
- shore platforms are found at the base of cliffs
- robin hood's bay
- horizontal dip of rocks
- shore platform protects cliffs and slows rate of erosion
49
how have cliffs eroded at robin hood's bay?
- cliffs at robin hood's bay retreated over the past 6000yrs
- now in equilibrium
50
explain how significant **geology** is in influencing the landforms on the Yorkshire coastline?
- **strongly influenced by geology**
- adjacent North York Moors comprise mainly sandstones, shales and limestones formed during Jurassic Period
- Flamborough Head = large chalk headland. cliffs are topped with glacial till
- differences in rock resistance are responsible for the varied coastal scenery, notably the high cliffs and bay/headland sequence
51
explain how significant **wave energy** is in influencing the landforms on the Yorkshire coastline?
- dominant waves affecting this coastline are N and NW, with a fetch of over **1500km**
- most exposed parts of coast are those that are northfacing and so these recieve the highest inputs of wave energy
- rates of erosion vary, partly due to these differences in wave energy inputs, but also due to variations in the resistance of the different geologies
- destructive waves dominate
52
explain how significant **sediment sources** is in influencing the landforms on the Yorkshire coastline?
- sediment cell 1, subcell 1D
- some sediment has been driven onshore as sea levels rose at the end of the last glacial period
- cliff erosion, including sandstone and chalk from the resistant rock outcrops + boulder clay deposits which yield significant amounts of gravel
- only river supplies limited amount of sediment due to weirs and reinforced banks built
- net ↑ in beach sediment of **9245 m3** 2008-11 at Saltburn
53
how significant is **sediment sources** in influencing the landforms on the Yorkshire coastline?
- would change seasonally as wave power changes
- (more erosion = more sediment input)
54
how significant is **geology** in influencing the landforms on the Yorkshire coastline?
- **most significant!!**
- varying hardness creates e.g. headlands and bays which *determines landform types*
- SCALE AFFECTS EVERYWHERE. if rock is very hard it will resist erosion irrespective of strength of wave energy
- chalk has faults = arches, stacks and geos etc. erodes at 0.1m/yr whereas weak clay erodes at rate of 0.8m/yr
- determines the speed of erosion
- time => consistent over time
55
how significant is **wave energy** in influencing the landforms on the Yorkshire coastline?
- may only be significant in winter storms
- wave energy is not the same all year round
- TIME = seasonal changes. more destructive waves in winter, day to day changes, *wave energy is not consistent*
- SCALE = some places are more exposed (e.g. Filey Brigg headland) where as Filey Bay is sheltered ∴ wave energy is more constructive.
56
how will bays on the yorkshire coast change over time?
- bays will be accumulating sediment during summer constructive wave periods
- but will be losing sediment in winter months due to storms
- e.g. Filey Bay
57
how will cliffs on the yorkshire coast change over time?
- lower part is strong rock with tightly bonded material (slow to erode via marine processes)
- cliff collapse is most likely but this will be a slow process, most likely in storms.
- the upper part of the cliff which is weaker will see a lot of biological weathering and mass movement (slumping) more regularly
- erosion here will happen more extensively in winter rather than summer
58
how will shore platforms on the yorkshire coast change over time?
- probably formed over last 600 years, but as a shore platform grows, it acts as its own breakwater
- ∴ waves will erode the shore notch making the platform bigger at a slower rate
- as a result this shore platform will not be growing quickly, unless sea level rise means that the waves can reach the base of the cliffs more regularly
59
how will stacks on the yorkshire coast change over time?
- over time, a stack will collapse to form a stump
- most likely during a winter storm after years of erosion
60
the features of flamborough head
- as the cliffs retreat a noticeable notch indicates how powerful wave energy can be
- vertical joints allow waves to penetrate the cliffs and together with faults these can lead to the formation of caves and geos.
- **wave quarrying** can result from the sheer weight of the waves striking the cliffs (hydraulic pressure) or from air being trapped in faults and acting pneumatically as waves break.
- **wave refraction** further concentrates waves on headlands allowing caves to develop progressively into arches, stacks and stumps.
- subaerial (cliff face) processes like rock falls are also important here and work together with cliff foot (sea) processes to create these headland features.
- at selwick's bay there are heavily faulted sections of chalk and where there is a master fault the wave energy has opened up to form a blow hole which will eventually develop into a geo.
61
what is the geology of robin hood's bay?
- lower lias shales
- the harder sandstones are more resistant to erosion and form the rocky sea cliffs to the N and S of the bay
- today the bay is 500m wide and is likely reaching an equilibrium
- the angle of dip is minimal (about 1 degree)
- therefore the shore platform is mostly flat
62
what happened with the Holbeck Hall Landslide?
- landslide destroyed 4 star hotel in June 1993
- cut back the 60 m-high cliff by 70 m.
63
what was the cause of the Holbeck Hall landslide
- While this landslide took place at the coast, the cause was not just simply erosion by the sea.
- It was likely a combination of driving factors including rainfall of **140 mm** in the two months before the slide took place,
- issues related to the drainage of the slope
- pore water pressure build-up in the slope
- and the type of geology.
64
green stacks pinnacle
- stack to stump
- high wave energy (long fetch, 1500km) concentrated on base
- mass movement events such as sudden rockfalls occur during a storm (probably winter)
- sub aerial processes such as salt crystallisation will also have impacted and weakened the chalk
- nothing for a long period then a sudden change
65
filey bay
- bay will gradually accumulate sediment, mostly in summer when we would expect *constructive* waves
- this will also steepen the beach profile
- waves refract/diverge around Filey Brigg headland
- LSD will be moving sediment N to S so bay will accumulate most in the south = gradual change
- may have a dynamic equilibrium in summer/winter due to changes in wave energy
66
what is lake El bullurus?
- 2nd largest lagoon found on the delta
- saltwater and 175m deep at its deepest point
67
what is lake Manzala?
- largest lagoon in egypt
- lagoons are enclosed by sand bars
68
what are sand bars?
- along the coast
- are developed by EASTWARD LSD
69
what are sabkahs?
- salt flats
- formed behind lagoons where older lagoons have dried out, leaving flat salt plains
70
where are coastal dunes found (nile delta)?
- developed between lakes manzala and El bullurus at Gamasa
71
what are crescentric bars?
- at alexandria
- formed by rip currents and onshore waves, with little LSD
72
what evidence is there that Nile delta is a low energy environment?
- small waves
- no erosional features like stacks or stumps etc
73
what landforms would you expect to find on the Nile Delta?
- depositional landforms:
- beaches
- bars and spits
- lagoons forming
- salt pans rather than mudflats, due to the heat
74
what is a delta?
large areas of sediment found at the mouths of many rivers
75
how are deltas formed?
1. the river splits into distributaries
2. this causes bars or islands of sediment to build up in the middle of the main channel
3. river spreads out and slows down as it approaches the sea
4. deposition is therefore encouraged as the velocity drops and the river becomes less efficient, the biggest sediment is dropped first and the finest further away (more friction)
5. layers of sediment build the delta out into the sea
76
where do deltas typically form?
- they form where rivers and tidal currents deposit sediment at a faster rate than waves and tides can remove it
- deltas typically form where:
1. rivers entering the sea are carrying large sediment broads
2. low energy environments exist in the coastal area
3. tidal ranges are low
77
what does the structure of deltas usually consist of?
the structure of deltas usually consist of 3 distinctive components:
1. **the upper delta plain** = furthest inland, beyond the reach of tides and composed entirely of river deposits
2. **the lower delta plain** = in the inter tidal zone, regularly submerged and composed of both river and marine deposits
3. **the submerged delta plain** = lies below mean low watermark and is composed mainly of marine sediments and represents the seaward growth of the delta
78
what is the upper delta plain?
furthest inland, beyond the reach of tides and composed entirely of river deposits
79
what is the lower delta plain?
in the inter tidal zone, regularly submerged and composed of both river and marine deposits
80
what is the submerged delta plain?
lies below mean low watermark and is composed mainly of marine sediments and represents the seaward growth of the delta
81
what is the nile delta?
- deltaic region in northern egypt
- 240km wide river delta
- arcuate (shaped like a bow; curved) delta where the majority of the Egyptian population lives
82
what are the key features of the nile delta coastline?
- the river nile
- its 2 main distributaries (**Rosetta and Damietta** branches)
- these distributaries are the **main sources of sediment**, and LSD is acting from west to east
- so drift aligned beaches, spits and barrier bars dominate
- prevalance of lagoons where spit growth has enclosed bays
83
what direction does LSD act in the nile delta?
from west to east, so:
- drift aligned beaches, spits and barrier bars dominate
84
how were the Burullus and Manzala lagoons formed?
- as their respective barrier bars enclosed the sea between 2 headlands
85
how is **sediment supply** a key historical reason for the delta's morphology?
- for a delta to form, it needs consistent sediment supply as these are fundamentally landforms of deposition
- the nile is the longest river in the world and much of its sediment flows from the ethiopian highlands, through Sudan and into Egypt.
- **120 million tonnes of sediment are moved annually.**
- the river traditionally flooded annually, and these floods deposited vast amounts of sediment onto the delta flood plains, creating incredibly fertile soils (up to 9.6m deep around Cairo)
- the sediment not being deposited on the flood plains will reach the Mediterranean Sea and be deposited due to *flocculation*, thus deposition is focused around the mouths of the distributaries.
86
where does the nile's sediment originate?
- the nile is the longest river in the world and
- much of its sediment flows from the ethiopian highlands, through Sudan and into Egypt.
87
how much sediment is moved by the nile?
120 million tonnes of sediment are moved annually.
88
what happens when the nile floods?
- the river traditionally flooded annually
- and these floods deposited vast amounts of sediment onto the delta flood plains, creating incredibly fertile soils (up to 9.6m deep around Cairo)
89
what happens to nile sediment not deposited onto flood plains?
- the sediment not being deposited on the flood plains will reach the Mediterranean Sea and be deposited due to *flocculation*
- thus deposition is focused around the mouths of the distributaries.
90
what are distributaries?
- the river in the delta breaks from being one large channel into several smaller ones called distributaries
- the 2 key ones being Rosetta and Damietta
91
which are the 2 key nile distributaries?
Rosetta and Damietta
92
how are **coastal processes** a key historical reason for the delta's morphology?
- mediterranean sea = low energy environment due to short fetch and no tidal range.
- winds are predominantly west/nw (60% of time), thus sediment is mostly reworked in an easterly direction.
- storms (and therefore high energy coastal events) are rare
- this means that the sediment being deposited at the mouths of the distributaries is gradually being reworked eastwards, creating spits which eventually become bars, behind which shallow lagoons form e.g. manzala and burullus
- where evaporation has taken place and there is no longer any water, salt flats/**sabkhas** remain
- to the east cresentric bars form where the beaches are swash aligned allowing rip currents to develop, which pull material out from the coastline and deposit it offshore
- there is also an extensive ridge of dunes which has been developed between the 2 lagoons at Gamasa beach. the dunes are about 30km across and result from the large backshore area being present here, the onshore winds allowing for aeolian processes to take place as well as the fact that dry warm conditions mean sand can dry out and be moved
- the winds coming in from the NW are able to entrain (pick up) huge amounts of sediment as the beach is up to 20km wide.
93
why is the mediterranean a low energy environment?
- the mediterranean sea is a relatively low energy environment
- due to the short fetch of the waves
- and lack of a tidal range
94
key features of the burullus lake
- has an elongated elliptical shape
- it is separated from the mediterranean sea by a narrow sand bar up to 3m above sea level at its NE corner
- agricultural wastes have been reported to increase sedimentation in wetlands and consequently diminish the size of lagoons such as Burullus.
95
what does agricultural waste do in wetlands?
agricultural wastes have been reported to increase sedimentation in wetlands and consequently diminish the size of lagoons such as Burullus.
96
where do cresentric bars form?
to the east, cresentric bars form where the beaches are **swash aligned**, allowing rip currents to develop, which pull material out from the coastline and deposit it offshore
97
how have dunes developed in the nile delta?
- there is also an extensive ridge of dunes which has been developed between the 2 lagoons at Gamasa beach.
- the dunes are about 30km across and result from the large backshore area being present here, the onshore winds allowing for aeolian processes to take place as well as the fact that dry warm conditions mean sand can dry out and be moved.
- the winds coming in from the NW are able to entrain (pick up) huge amounts of sediment as the beach is up to 20km wide.
98
how have coastal processes and sediment deposition combined to change the deltas morphology?
- these coastal processes, combined w/ sediment deposition, have meant that traditionally the delta has been "growing", extending out into the Mediterranean Sea, and reworked by the LSD moving eastwards
- the lagoons have, over time, been getting filled in by fine sediment which is no longer reworked by LSD
99
what is happening to nile lagoons over time?
the lagoons have, over time, been getting filled in by fine sediment which is no longer reworked by LSD
100
how will the landscape of the nile delta change over time due to **building of the Aswan Dam, 1964**
- by FAR the **most significant change to the region**
- done to ensure a water supply for the growing population of Egypt and produce HEP
- it massively **reduced the water and sediment supply downstream**, and ∴ to the delta
- about 120 mill tonnes of sediment used to flow, and now virtually none does, causing the delta to erode/retreat by up to **148m** per year
- areas most affected are by mouths of the distributaries due to lack of sediment supply
- BUT eastern ends of the bars which help create the lagoons are still growing as the sediment is moved steadily eastwards by LSD
- this has degraded the agricultural land as the soils are less rich and fertile (which is significant as it is forcing people to move from traditional farming practises into fish farming in the lagoons, which is putting pressure on these fragile ecosystems)
- if the bars which currently shelter them get eroded due to lack of sediment supply, the fish farming and economic potential is lost too
- clearly this is an **unsustainable approach** as in time the landforms will be eroded fully.
101
how much does the delta retreat by each year?
- about 120 mill tonnes of sediment used to flow, and now virtually none does
- causing the delta to erode/retreat by up to **148m per year**
102
how are the main distributaries changing as a result of the Aswan Dam?
- the Rosetta mouth is being eroded by **24m/yr**
- the Damietta mouth by **36m/yr**
- this has degraded the agricultural land as the soils are less rich and fertile (which is significant as it is forcing people to move from traditional farming practises into fish farming in the lagoons, which is putting pressure on these fragile ecosystems)
- if the bars which currently shelter them get eroded due to lack of sediment supply are lost, the fish farming and economic potential is lost too
- clearly this is an unsustainable approach as in time the landforms will be eroded fully.
103
what has ethiopia done, similarly to Egypt?
- built a large dam to store water for its own industry and growing population, as well as generate electricity
- has lead to some serious political issues as this would inhibit the sediment and water supply even further
104
how will the landscape of the nile delta change over time due to **consistent wave and wind energy**?
- there are dominant winds (from NW in summer and NE in the winter)
- these will steadily and consistently rework sediment via LSD to increase the size of the onshore bars and spits
- although the seasonal difference in winds will cancel out some of the LSD
- the wind energy also moves sand from the Burullus sand bar landward, which then reduces the size of the Burullus Lagoon
- the highway developed along the coast has not helped this as it has caused drying of the sand plus brought more people to the dunes, which has meant that the wind is now able to erode these dunes more easily
105
where are the dominant nile delta winds?
from NW in summer and NE in the winter
106
how will the landscape of the nile delta change over time due to **climate change**?
- sea levels are expected to rise between **18 and 64cm by 2100**
- this will increase flood risk and of the delta being inundated with sea water (which, being saline, could lead to farm land becoming infertile, thus having an enormous economic impact)
- there could be up to **60%** loss of farmland by 2100
- the rate of coastal retreat will likely increase, thus reducing the land available for human habitation
- drinking water supplies and aquifers could be threatened as well
- this inundation of salt water is perhaps the biggest issue for Egypt as so many people and their source of income/water etc. comes from this
107
how did the Nile Delta fundamentally form?
- the Nile Delta fundamentally formed under different conditions than are operating now (most significantly the sediment source)
- the river used to bring more sediment from the Ethiopian highlands but the Aswan Dam has reduced river flow and massively reduced sediment supply, causing the shore to retreat by up to 148m annually
108
how does LSD play a role in the Nile Delta?
- in moving sediment and reworking landforms but is not providing a large sediment source
- the reduced sediment supply has led to the erosion of the coastline, most notably around the mouths of the distributaries Rosetta and Damietta
109
what will change to landforms be like in the Nile Delta?
- likely to be far more gradual and happen at an even rate compared to high energy coastlines (which will experience storms, causing arches to collapse eg)
- the landforms to the west will lose sediment more rapidly whereas the ones to the east will benefit from sediment supplied via LSD
- human actions could potentially significantly alter the rate of change in a positive manner through inputting sediment artificially/sea defences
110
how did the **Damietta spit** form?
- generated by eastward LSD currents from mouth of distributary
- when there is a natural hallow in the coastline
- sediment build up going eastwards due to dominant summer wind direction
- net movement of material from W -> E forms the spit
111
how did the **Burullus/Manzala Lagoon** form?
- closed off sediment from sea = fine sediment
- formed along coastal plains
- LSD forming the Rosetta Bar traps brackish water
- shallow basin near shore, gradually erodes backwards
112
how did the **Gamsa sand dunes** form?
- when sand completely dries out between high tides, onshore winds blow that sand landwards and it becomes trapped by dune grasses and vegetation => accumulates layers of hard sand
- aeolian processes e.g. **saltation**
- positive sediment budget
113
how did the **rosetta onshore bar** form?
- more exposed to easterly winds => ↑ LSD => ↑ sediment build up
- coastline is more drift aligned here
114
how did the **Sabkahs** form?
- where older lagoons have dried out
- water evaporates until only salts remain
115
how did the **cresentic bar at Alexandria** form?
- due to swash aligned beach and lack of LSD
- formed by RIP CURRENTS which are pulling sediment back from the coastline and depositing offshore
- onshore waves with little LSD
- winter
116
how will the **damietta spit** change over time?
- becomes recurved due to wave refraction and secondary wind direction
- would get small due to no new sediment = western end gets thinner and potentially flooded by sea level rise
- gradually migrate SE as wind blows in that direction
117
how will the **burullus lagoon** change over time?
- modified by erosion and deposition
- sediment supply has decreased and sea levels increased => more energy/larger waves drown lagoons
- dry out due to thermal energy
- sea level rise may breach/erode bar
- slow, LT change. bars vulnerable due to no new input
118
how will the **gamsa sand dunes** change over time?
- the seasonal changes in wind direction reshape dune and creates ridges
- can travel along beach (aeolian) SOUTHWARDS
- fairly significant changes
- gets smaller due to lack of sediment input
- increased tourist use of dunes destroys vegetation
119
how will the **rosetta onshore bar** change over time?
- same as damietta spit
- extend to form lagoon
- smaller as sea levels increase
- deprived of sediment from dam
120
how will the **sabkahs** change over time?
- takes 1000s of years to change and build up layers of salt crust
- lagoons drained for farming therefore more sabkahs over time
121
how will the **cresentric bar at alexandria** change over time?
- coastal management
122
what is the **damietta spit's** interrelationship with other landforms in the delta?
- could become a bar
- bars trap water in behind to form lagoons
123
what is the **burullus lagoon's** interrelationship with other landforms in the delta?
- found either side of ridges/headlands (its the depressions between them)
- on the outskirts of the lagoon, flocculation leads to deposition of fluvial sediment
- and evaporation = sabkahs
124
what is the **gamsa sand dune's** interrelationship with other landforms in the delta?
- between Manzala and Bullurus
- if beaches disappear due to sea level rise dunes will have no sediment input and will deflate
125
what is the **rosetta onshore bar** interrelationship with other landforms in the delta?
to the east of where the Rosetta distributary mouth reaches the sea
126
what is the **sabkah's** interrelationship with other landforms in the delta?
- behind lagoons/ where old lagoons have dried out
127
what is the **cresentric bar at Alexandria's** interrelationship with other landforms in the delta?
- bars absorb wave energy so it reduces it
- by time it reaches beach = more deposition (negative feedback)
128
what are the inputs of the Nile Delta?
- fluvial sediment = the NILE (**used to be 120 mill tonnes/year**)
- wave energy = small, consistent low energy
- thermal/solar energy = salt pans
- wave direction NW
129
what are the processes of the Nile Delta?
- LSD
- waves moving on and off beach
- aeolian processes moving sediment to Gamasa dunes
- evaporation leading to Sabkahs
130
what are the outputs of the Nile Delta?
- erosion increase due to Aswan Dam, of the Nile in SE
131
how are the **Burullus lagoon** and **Rosetta Bar** interlinked?
- as bar forms due to LSD, they extend to enclose lagoon
- lack of new sediment erodes bar = lagoon breached
132
how are the **Burullus lagoon** and **sabkahs** interlinked?
- lagoons drained for agriculture and farming (but fairly infertile)
- lagoons dry out due to thermal energy
= water evaporates and salt remains
133
how are the **Gamsa sand dunes**, **sediment supply from Nile** and **Rosetta Bar** interlinked?
sediment reaches bar from river then blows onto dunes
134
how are the **Gamsa sand dunes** and **sediment supply from Nile** interlinked?
- as supply decreases due to construction of dam, dunes decrease in size
- a continual supply is required
135
how are the **Damietta spit** and **Rosetta Bar** interlinked?
- rosetta bar (west of spit) affects Damietta Spit as LSD will rework sediment from bar eastwards to the spit
- slow, gentle, LT process
136
how are the **Damietta spit** and **wave energy** interlinked?
- LSD (from dominant W->E waves) moves sediment down coast until it projects out into sea = spit
- spit recurves due to stronger wave energy in deeper water
137
how could building coastal defences influence the Nile delta coastline and sediment budget?
- reduced sediment supply has led to erosion of the coastline most notably around mouths of distributaries Rosetta and Damietta
- this can be viewed as an unintentional change to coastal environment as the Aswan Dam was intended to manage River Nile and generate HEP rather than change the coastline, but it almost certainly has had an impact
