Physical Landscape Flashcards
(90 cards)
1
Q
Where is Lyme Regis?
A
Lyme Regis is a small coastal town in Dorset, on England’s south coast
2
Q
What are the issues in Lyme Regis? (4)
A
Unstable cliffs, powerful waves from the south west cause rapid erosion, foreshore erosion has destroyed/damaged properties, sea walls have been breached many times
3
Q
What was the Lyme Regis scheme called and when did it start?
A
Lyme Regis Environmental Improvement Scheme was set up in early 1990s and completed in 2015
4
Q
What was the phase 1 and 2 of the scheme?
A
- new sea walls and promenades
- cliffs stabilised
- creation of wide sand and shingle beach to absorb wave energy
- extension of rock armour to absorb wave energy and retain beach
5
Q
What was phase 3 of the scheme?
A
It didn’t go ahead as costs outweighed the benefits
6
Q
What was phase 4 of the scheme?
A
- new sea wall for extra protection
- cliffs stabilised to protect homes
7
Q
What was the cost of the Lyme Regis Scheme?
A
£43 million
8
Q
What were the positive outcomes of Lyme Regis scheme?
A
- new beaches have increased visitor numbers and seafront businesses are doing well
- new defences have withstood stormy winters
- harbour is better protected
9
Q
What were the negative outcomes of Lyme Regis scheme?
A
- increased visitor numbers has caused conflict due to traffic congestion and litter
- some think the new defences spoil the landscape
- the new sea wall might interfere with natural processes and cause problems elsewhere
10
Q
Where is the River Tees?
A
In the North East England and its source is in the Pennine Hills. It flows roughly east to reach the North Sea at Middlesbrough
11
Q
What is a landform of erosion on the River Tees?
A
High Force - in the upper course, the waterfall drops 20m and continues through a gorge
12
Q
Describe the rock type on High Force
A
- A resistant band of igneous rock (dolerite) cuts across the valley. Its resistance has led to the development of a waterfall
- Underlying weaker rock (limestone) is undercut
- Waterfall retreats upstream to form a gorge
13
Q
What are examples of depositional landforms in the River Tees?
A
- meanders
- levees
- floodplains
14
Q
Where is Banbury?
A
- 50km north of Oxford in the Cotswold Hills
- population of 45 000
- much of the town is on the floodplain of the River Cherwell
15
Q
Why was the Banbury scheme needed?
A
- in 1998 flooding closed the railway station, shut roads and caused £12.5 million of damage
- in 2007, it was flood again (along with much of central and western England)
16
Q
What has been done for the Banbury scheme?
A
- the embankment created a flood storage area mainly on the floodplain of the River Cherwell
- the A361 in the flood storage area has been raised
- flow control structures control the rate of flow towards Banbury. Excess water builds up in the storage area
17
Q
What are the social benefits of the Banbury Scheme?
A
- the raised A361 stays open during a flood avoiding disruption
- quality of life improved with new footpaths and green areas
- less anxiety about flooding
18
Q
What are the economic benefits and costs of the Banbury Scheme?
A
- the scheme cost £18.5 million, paid for partly by the Environment Agency and Cherwell District Council
- Over 400 houses and 70 businesses protected at a value of over £100 million
19
Q
What are the environmental benefits and costs of the Banbury Scheme?
A
- Earth needed to build embankment was extracted locally, creating a small reservoir
- A new habitat has been created with ponds, trees and hedges
20
Q
What are the 3 levels of flood warnings?
A
- Flood watch: flooding of low-lying land and roads expected
- Flood warning: threat to homes and businesses
- Severe flood warning: extreme danger to life and property. Stay upstairs or leave him
21
Q
What makes a low, flat hydrograph?
Basin size, drainage density, rock type, land use, relief, rainfall intensity, soil moisture
A
Basin size: large basins result in a relatively slow water transfer
Drainage density: low density leads to slower transfer
Rock type: permeable rocks encourage slow transfer
Land use: forests slow down water trasnfer
Relief: gentle slopes slow down water transfer
Rainfall intensity: light rain will transfer slowly and most will soak into the soil
Soil moisture - dry soil soaks up water and slows down its transfer
22
Q
Explain longshore drift
A
where waves approach the beach at an angle, sediment moves along the beach in a zig zag pattern where the swash carries material up along the beach and the backwash carries material back down the beach at right angles which is a result of gravity
23
Q
Define transportation and what are the 4 types
A
the movement of eroded material
1) solution
2) suspension
3) traction
4) saltation
24
Q
Describe the 4 methods of transportation
A
Solution - dissolved chemicals often derived from limestone or chalk
Suspension - particles carried within the water
Traction - large pebbles rolled along the seabed
Saltation - a ‘hopping’ or ‘bouncing’ motion of particles too heavy to be suspended
25
What is the lag time?
time in hours between the highest rainfall and the highest discharge
26
What affects the shape of a hydrograph?
affected by the rainfall and by drainage basin characteristics
27
What makes a flashy hydrograph?
Basin size, drainage density, rock type, land use, relief, rainfall intensity, soil moisture
Rainfall intensity: heavy rain exceed infiltration capacity of vegetation
Basin size: small basins often lead to rapid water transfer
Drainage density: high density speeds up water transfer
Rock type: impermeable rocks encourage rapid overland flow
Land use: urbanisation encourages rapid water transfer
Relief: steep slopes lead to rapid water transfer
Soil moisture: saturated soil results in rapid overland flow
28
The size and energy of waves depends on 3 things, what are they?
1) Fetch of wind - distance wind travels, longer the fetch, the bigger the wave
2) Power of wind
3) Duration of wind
29
Describe biological weathering
- plant roots grow in cracks in rocks
- animals burrow into weak rocks
30
Describe salt cracking
- seawater contains salt
- water evaporates, leaves sea crystals in cracks and holes, these salt crystals grown and expand
- puts pressure on the rocks and flaks may eventually break off
31
Describe freeze-thaw weathering
- water collects in crack
- at night, water freezes and expands and makes crack in the rock bigger
- when the temp rises, water will seep deeper into the rock
- after repeated freezing and thawing, fragments of rock may break off and fall to the foot of the cliff
32
Describe chemical weathering
Carbonation
- rainwater absorbs carbon dioxide from the air becoming slightly acidic
- contact with alkaline rocks e.g limestone produces a chemical reaction causing rocks to slowly dissolved
33
Define erosion
wearing away and removal of material by a moving force such as a breaking wave
34
What are the 4 types of erosion and explain them?
Hydraulic action - powerful waves hit cliffs
Abrasion - fragments of rock are picked up and hurled at the cliff
Attrition - rock fragments collide with each other -> rounder, soft pebbles
Solution - chemicals in the rocks are dissolved and are often derived from limestone and chalk
35
Define deposition
occurs when material being transported by the sea is dropped due to the sea losing energy
36
What is longshore dirft?
A process of transportation that shifts eroded material along the coastline
37
What landforms occur in rivers?
Upper - erosional landforms e.g waterfalls
Middle - most erosional and deposition landforms e.g meanders + transportation
Lower - depositional landforms e.g levees
38
What are interlocking spurs?
- a mountain stream erodes vertically creating a V-shaped valley
- it winds around areas of resistant rock to create interlocking spurs
39
What are the disadvantages of sea walls?
Social: they can look unnatural
Economic: very expensive £5000-£10000 per metre and expensive to maintain
Environmental: waves can erode the sea wall
40
What are the pros of gabions?
Social: does not impede access to the beach
Economic: cheap
Environmental: can improve cliff drainage and eventually become vegetated and merge into landscape
41
What are the cons of gabions?
Social: looks unnatural
Economic: cages rust within 5-10 years
Environmental: not very strong
42
What are the methods of soft engineering?
1) Dune regeneration
2) Dune fencing
3) Beach nourishment
43
What are the cons of groynes?
Social: beach on the downdrift side can be lower than the updrift side so it
Environmental: interrupting longshore drift can increase erosion elsewhere
Economical: regular maintenance needed, ineffective during storm conditions
44
What are the pros of groynes?
Social: builds a beach which encourages tourism, acts as windbreaks for people
Economic: more tourism, not too expensive, well maintained can last 40 years
Environmental: trap sediment being carried by longshore drift
45
Describe the soft engineering methods
Dune regeneration: strengthen dunes by building it up and marram grass
Dune fencing: fences are constructed along the seaward face of existing dunes to encourage new dune formation
Beach nourishment: adding sand and shingle by building up beach material, creates a wide, sandy beach, reducing erosion of cliffs
46
What are the pros of dune regeneration?
Environmental: maintains a natural looking coastline, increasing biodiversity
Economic: cheap
Social: better barrier between land and sea
47
What are the cons of dune regeneration?
Environmental: can be damaged by storms
Economic:
Social: temporarily fencing off the dunes, time consuming
48
What are the 4 types of mass movement?
1) Rockfall - rock breaks away often due to freeze-thaw
2) Landslide - blocks of rock slide downhill
3) Mudflow - saturated soil and weak rock flows downhill
4) Rotational slip - slump of saturated soil and weak rock along a curved surface
49
What are the benefits of managed retreat?
Social - buffer to erosion as salt marshes store large quantities of water, reduce flooding to nearby communities. Salt marsh food place to walk
Economic - cows which graze on salt marsh grasses have a high percentage of salt favoured by consumers. Tourists may spend money in local businesses
Environmental: creation of a natural salt marsh and mudflat provides a sanctuary for many habitats and wildlife to flourish
50
What are the cons of beach nourishment?
Environmental - offshore dredging of sand and shingle increases erosion in other areas, affecting wildlife
Economical - large storms will require further beach replenishment, costs increase
Social - many people may be prevented from the beach for several weeks
51
What are the pros of beach nourishment?
Economical - relatively cheap, easy to maintain
Social - retains natural appearance, could attract tourists
Environmental - natural defences against erosion
52
What are the cons of dune fencing?
Social - can be unsightly, especially if fences become broken
Economical - regular maintenance needed especially after storms
53
What are the pros of dune fencing?
Environmental - little impact on natural systems
Economical - relatively cheap
54
What is hard and soft engineering?
Hard engineering - uses artificial structures to control natural processes
Soft engineering - involves methods that work with natural process
55
What is coastal deposition?
when the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying
56
When is coastal deposition most likely to occur?
- swash stronger than backwash
- shallow water
- not much power of the wind so a slow wind speed (near a sheltered area such as a bay or a combe)
57
Describe how mudslides occur
- when saturated soil and weak rock flow down a slope
- typically occur where rocks are made up of boulder clay
58
Define weathering and mass movement
Weathering - breaking down of the rock in situ and not moved
Mass movement - downhill movement of weathered material under the force of gravity
59
What is a drainage basin?
the area of land drained by a river and its tributaries
60
How does a river's long profile change?
- steep in upper course
- gentle gradient in middle course
- very gentle gradient in lower course
61
How does the river's cross profile change downstream?
- V-shaped valley and steep sided
River: narrow, shallow, turbulent
- Floodplain - wider flat, floor
Wider and deeper
- Levees - very wide and flat
River: wide, deep, large sediment load
62
Why does a river's cross profile change?
channel erosion - as tributaries add more water to the river, it erodes its channel, making it wider and deeper
63
What is the source?
start of a river
64
What is a tributary?
a small stream that joins a larger river
65
What is a confluence?
where a tributary joins a larger river
66
What is a mouth?
the end of a river, usually where it joins the sea
67
What is a watershed
the edge of a river basin
68
When does deposition happen?
- when a river's velocity decreases and it no longer has the energy to transport its load, it deposits it
- large rocks (traction) - short distances during high flow deposited in upper course
- smaller sediment deposited downstream (suspension). Deposited on river's bed where velocity slows down due to friction
- deposition at mouth - velocity reduces because of the gentle gradient and and interaction with tides
69
Why is a drainage basin an example of an open system?
- open to inputs from outside, such as precipitation and is responsible for outputs out of the system such as output of water into the sea and evaporation of water into the atmosphere
70
What is a river's cross profile and long profile?
side to side cross section of a river channel and/or valley
gradient of a river, from its source to its mouth
71
What are the 3 types of weathering?
- Physics (mechanical)
- Biological
- Chemical
72
What is the difference between concordant and discordant coastlines?
Concordant:
- lines run parallel
- creates coves
- only 1 rock type
Discordant:
- perpendicular
- creates bays and headlands
- many rock types
73
What are the features of constructive waves?
Wave height, wave length, swash, backwash, frequency
Wave height: <1m
Wave length: long
Swash: strong
Backwash: weak
Frequency: low 8-10 waves per minute
Deposit material
74
What are the features of destructive waves?
Wave height, wave length, swash, backwash, frequency
Wave height: >1m
Wavelength: short
Swash: weak
Backwash: strong
Frequency: high 10-14 waves per minute
Erode
75
What factors influence coastal landforms?
Rock type - some rocks are tougher and more resistant to erosion that others. Softer rocks are more easily eroded
Geological structure - includes the way that rock has been folded or tilted
76
How are dunes formed?
- embryo dunes form around obstacles (e.g rocks)
- dunes develop and are stabilised by vegetation (e.g marram grass) to form fore dunes and tall yellow dunes
- decomposing vegetation makes sand more fertile and a wider range of plants colonise the back dunes
- Ponds (dune slacks) can form in depressions
77
How are spits formed?
- formed by the deposition of sediments transported by longshore drift
- over time, the deposited material builds up and extends into the sea, forming a spit
- spits often have a hooked or curved end due to wind and wave direction changes
78
How are bars formed?
bars are formed when a spit grows across a bay or when there is significant sediment between two headlands due to wave action and longshore drift
79
List the examples of hard engineering for rivers
- Dams and reservoirs
- Channel straightening
- Embankments
- Flood relief channels
80
What is channel straightening?
- cutting through meanders creating a straight channel, speeding up water flow. But can increase flood risk downstream
- straightened channels may be lined with concrete -> unattractive and can damage wildlife habitats
81
What are embankments?
- raising the level of a river bank allowing the channel to hold more water to help prevent flooding
- concrete or stone walls often used but mud dredged from the river can be used
++ cheaper, more sustainable, looks natural
- higher maintenance
82
What is a flood relief channel?
- built to by pass urban areas
- at times of high flow, sluice gates allow excess water to flow into the flood relief channel, reducing the threat of flooding
++low insurance costs, footpaths + tracks built along and new habitats
- people have to move
- expensive
- construction -> habitats disturbed
83
What are 4 soft engineering methods?
- afforestation
- wetland and flood storage areas
- floodplain zoning
- river restoration
84
What is afforestation?
trees obstruct the flow of water and slow down its transfer to river channels
++ sustainable
++ cheap
- time consuming
- does not help in serious flooding
85
What are wetlands and flood storage areas?
wetlands are deliberately allowed to flood, forming storage areas
++ effective for strong water as it reduces the risk of flooding downstream
++ habitats for wildlife
- if used for sport pitches, will be flooded every so often
86
What is flood plain zoning?
- restricts different land uses to certain zones on the floodplain
- areas at risk from flooding can be used for grazing, parks and playing fields
++ reduce damage as more expensive buildings are far away
-- difficult to predict how bad a flood and therefore how far away from the river the high value property
-- hard to change existing land
87
How are meanders and ox bow lakes formed?
- meanders are bends in a river found mainly in lowland areas. They constantly change shape and position
- Thalweg - fastest current, swings from side to side causing erosion on the outside bend and deposition on the inside bend
- processes cause meanders to migrate across the valley floor
88
How are oxbow lakes formed?
as meanders migrate across the valley floor they erode towards each other, eventually forming an ox bow lake
- neck of meander is gradually eroded
- the meander neck is cut through completely leaving an ox bow lake
89
What are floodplains and how are they formed?
wide, flat areas on either side of a river in its middle and lower courses. Created by migrating meanders and floods depositing layers of silt to form aluminium
90
How are levees formed?
form when in low flow, deposition raises the river bed so the channel can't carry as much water
during flooding, water flows over the sides of the channel
as velocity decreases, coarser sediment is deposited first on the banks - then finer sand and mud, raising the height of the levees
