paper 1, section c, physical landscapes in the uk Flashcards
1
Q
what is relief?
A
the physical features of the landscape (height above sea level, steepness of slopes and shape of landscape features)
2
Q
what is relief determined mainly by?
A
geology (rocks)
e.g. granite and slate - dramatic mountain ranges (Arran in Scotland), clay and limestone - low-lying plains and gently rolling landscapes
3
Q
what is the highest mountain in the UK?
A
Ben Nevis (1347m)
4
Q
how do waves form?
A
- wind blowing over the sea
- friction with the surface = ripples = waves
5
Q
what is fetch?
A
distance the wind blows across the water
- the longer the fetch, the more powerful the wave
6
Q
what happens when waves reach the coast?
A
- in the open sea, despite wavy surface, there is little horizontal movement of water
- when waves approach shore there’s forward movement of water as waves break and surge up the beach
- the seabed interrupts the circular movement of the water
- as the water becomes shallower, the circular motion becomes more elliptical
- this makes the crest of the wave rise up and eventually collapse onto the beach
7
Q
what is swash?
A
the water that rushes up the beach
8
Q
what is backwash?
A
the water that flows back towards the sea
9
Q
what are the 2 types of wave?
A
- constructive waves
- destructive waves
10
Q
what are some characteristics of constructive waves?
A
- low waves
- surge up the beach and ‘spill’ with powerful swash
- carry and deposit large amounts of sand and pebbles = ‘construct’ beach = more extensive
- preferred by surfers = longer rides
- formed by storms 100s km away
11
Q
what are some characteristics of destructive waves?
A
- formed by local storms - close to the coast
- can erode beach
- high wave frequency - often interfere with each other - chaotic mass of water
- high and steep = plunge onto beach
- little forward motion (swash) when it breaks but powerful backwash = removal of sand and pebbles = gradual destruction of the beach
12
Q
wave height of constructive wave?
A
low
13
Q
wave height of destructive wave?
A
high
14
Q
wave length of constructive wave?
A
far/long
15
Q
wave length of destructive wave?
A
short
16
Q
type of wave (spilling or plunging); constructive wave?
A
spilling
17
Q
type of wave (spilling or plunging); destructive wave?
A
plunging
18
Q
strength of swash of constructive wave?
A
strong
19
Q
strength of swash of destructive wave?
A
weak
20
Q
strength of backwash of constructive wave?
A
weak
21
Q
strength of backwash of destructive wave?
A
strong
22
Q
net beach sediment (gain or loss) for constructive wave?
A
gain
23
Q
net beach sediment (gain or loss) for destructive wave?
A
loss
24
Q
what is weathering?
A
the weakening or decay of rocks in their original place on, or close to, the ground surface
25
what are the 3 types of weathering?
1. mechanical (physical)
2. chemical
3. biological
26
what is mechanical/physical weathering?
the disintegration of rocks, often resulting in scree (pile of rocks) found at the foot of the cliff
27
what is chemical weathering?
caused by chemical changes; rainwater is slightly acidic which very slowly dissolves certain types of rocks and minerals
28
what is biological weathering?
due to actions of flora and fauna e.g. plants roots crack into the rocks, animals burrowing etc
29
what are some weathering processes?
1. salt weathering
2. carbonation
3. freeze-thaw
30
describe salt weathering
mechanical
- when seawater evaporates it leaves behind salt crystals
- these grow and expand in cracks putting pressure on the rocks = flakes eventually break off
31
describe carbonation
chemical
- rainwater absorbs CO2 from the air, becoming slightly acidic
- contact with alkaline rocks creates chemical reactions = slowly dissolve e.g. limestone and chalk
32
describe freeze thaw
mechanical
- water collects in cracks in rock
- water freezes to form ice and causes stresses and cracks are enlarged
- after repeated freezing and thawing, rock fragment breaks off and collects as scree at the foot of the rock face
33
what is mass movement?
the shifting of rocks and loose material down slope under the influence of gravity
34
what are the coastal erosion processes?
- hydraulic power
- corrosion/solution
- attrition
- corrasion/abrasion
35
what is hydraulic power?
the power of the water
36
what is corrosion/solution?
the chemical breakdown of the rocks
37
what is attrition?
the wearing away of the rock material as they hit each other
38
what is corrasion/abrasion?
the sandpapering effect of the broken away material thrown back at the coast
39
what are the coastal transportation processes?
- suspension
- solution
- traction
- saltation
40
what is suspension?
fine material such as clay and sediment is carried by the sea
41
what is solution (transportation)?
dissolved minerals are carried by the sea
42
what is traction?
large boulders and pebbles are rolled along the sea bed
43
what is saltation?
small stones, pebble and silt bounces along the sea bed
44
what is longshore drift and how does it work?
- movement of sediment on the beach depends on the direction that the waves approach the coast
- if the approach is 'head on' sediment will move up and down
- if they approach at an angle = move along the beach in a zigzag pattern = longshore drift = beaches and spits
- the backwash carries the sediment back down the beach as the wave retreats to the sea
45
what is coastal deposition?
- it happens when there is lots of erosion elsewhere on the coast, meaning there's lots of sediment available
- that sediment is then dropped in areas where the flow of the water slows down (loss of energy), usually where the coastline changes direction e.g. in sheltered bays: mudflats and salt marshes are often found in sheltered estuaries behind spits
46
what are some coastal erosion landforms?
- headlands and bays
- cliffs and wave-cut platforms
- caves, arches and stacks
47
information about headlands and bays
- common coastal landforms
- usually form where rocks of different strength are exposed
- weaker bands of clay are eroded more rapidly than the neighbouring bands of more resistant sandstone and limestone
- over time, the eroded clay forms bays where, under sheltered conditions, sediment is deposited to form beaches
- the more resistant rocks stick out into the sea to form headlands which are often battered by powerful waves to form steep cliffs
- deposition does not occur due to the lack of shelter at headlands (this explains the absence off beaches)
48
what are examples of headlands and bays?
Duriston Head
- limestone
- steep sides
- high energy area affected by destructive waves
- hard rock jutting out to sea
Swanage Bay
- crescent shaped
- soft roc such as sand and clay forming a crescent shape
- low energy constructive waves
- two headlands mark the edges of the bay
49
information about cliffs and wave-cut platforms
- when waves break against a cliff, erosion close to the high tide line will wear away the cliff to form a wave cut notch
- over a long period of time (hundreds of years) the notch will get deeper and deeper, undercutting the cliff
- eventually, the overlying cliff can no longer support its own weight and it collapses
- through continual sequence of wave-cut notch formation and cliff collapse, the cliff will gradually retreat
- in its place will be a gently sloping rocky platform called a wave-cut platform
- a wave-cut platform is typically quite smooth due to the process of abrasion
- however, in some places it may be scarred with rock pools
50
information about caves, arches and stacks
- starts with a joint or fault in resistant rock
- abrasion and hydraulic action widen the join to form a cave
- waves make the cave larger until it cuts through the headland to make an arch
- the arch is eroded and the roof becomes too heavy and collapses
- this leaves a tall stack
- the stack is eroded and collapses, leaving a stump
51
how do hard and soft rocks affect landforms?
- hard rocks such as granite, limestone and chalk are tougher and more resistant to erosion than soft rocks such as clays and sands
- the harder rocks form impressive cliffs and headlands that point out to sea, whilst soft rocks form bays or low-lying stretches of the coastline
52
what is a concordant coastline?
rocks are parallel to the wave front and therefore rates of erosion are similar along the coastline
53
what is a discordant coastline?
differential erosion may occur, where bands of hard and soft rock outcrop at right angles to the sea
54
what are some coastal depositional landforms?
- beaches
- sand dunes
- sand spits and bars
55
what are beaches?
deposits of sand and shingle (pebbles) at the coast:
- sandy beaches are mainly found in sheltered bays; the waves entering the bay are constructive waves, they have a strong swash and build up the beach
- some beaches aren't made of sand; lots of the coast in the south of England have pebble beaches; these high energy environments wash away finer sand and leave larger pebbles (these come from nearby eroded cliffs or are deposited onshore from vast accumulations out to sea)
56
what are sand dunes?
accumulations of sand grains, shaped into mounds or ridges by the wind under the influence of gravity; they are found at the back of beaches above the maximum reach of the waves
57
how are sand dunes formed?
- embryo dunes form around deposited obstacles such as pieces of wood or rocks
- these develop and stabilised by vegetation to form fore dunes and tall yellow dunes; marram grass is adapted to the windy, exposed conditions and has long roots to find water, these roots help bind the sand together and stabilise the dunes
- in time, rotting vegetation adds organic matter to the sand making it more fertile; a much greater range of plants colonise these 'back' dunes
- wind can form depressions in the sand called dune slacks, in which ponds may form
58
what does a sand dune need to form?
- a large, flat beach
- a large supply of sand
- a large, tidal range, so there is time for the sand to dry
- an onshore wind to move sand to the back of the beach
- an obstacle such as drift wood for the dune to form against
59
how are spits formed?
1. longshore drift transports sand along the coast
2. the coastline changes direction and the waves begin to lose energy
3. deposition starts to build up at the proximal end and the spit grows out into the sea
4. the spit is exposed to changes in wind and wave direction which cause the distal end to hook back towards the land
60
how are bars formed?
1. a spit may continue to grow across a bay due to LSD
2. freshwater is trapped behind it to form a lagoon
3. this feature is called a bar
61
what are the two types of engineering used for coastal management?
hard engineering and soft engineering
62
what is hard engineering?
- use of artificial structures to control natural processes
- options tend to be expensive, short-term
- they may also have a high impact on the landscape or the environment and be unsustainable
63
what is soft engineering?
- often much less expensive than hard engineering options
- usually more long-term and sustainable, with less impact on the environment
64
what are the hard engineering methods of coastal management?
- sea wall
- groynes
- rock armour
- gabions
65
what are the soft engineering methods of coastal management?
- beach nourishment/reprofiling
- dune regeneration
- dune fencing
66
what are sea walls?
- concrete or rock barrier against the sea, placed at the foot of cliffs or at the top of a beach
- has a curved face to reflect the waves back into the sea
- costs around £5,000-£10,000 per metre
67
advantages/disadvantages of sea walls?
advantages
- gives people a sense of security and often has a walkway
- if well maintained, they can be effective for many years by making the cost worthwhile
disadvantages
- very expensive and encounter high maintenance costs
- from the beach, a sea wall is ugly to look at
- sea walls may also destroy habitats
68
what are groynes?
- timber/rock structures built out to the sea from the coast that slow down and trap sediment moved by longshore drift to allow beaches to build up
- cost £150,000 every 200m
69
advantages/disadvantages of groynes?
advantages
- if well maintained, can last up to 40 years
- some groynes have concrete crests for people to walk along to reach a viewing or fishing point and also acting as windbreaks
disadvantages
- barriers which impede walking along a beach
- may be considered unattractive, especially old and degraded ones
70
what is rock armour?
- piles of large boulders placed at the base of the cliff, forcing waves to break, absorbing energy and protecting the cliffs
- costs around £200,000 per 100m
71
advantages/disadvantages of rock armour?
advantages
- piles of large boulders placed at the base of the cliff which protects the cliffs
- often used as a platform for fishing
disadvantages
- imported rocks do not blend in with the local geology
- rock armour is ugly and it often covers vast areas of a beach
- litter can become trapped in the structure
72
what are gabions?
- wire cages filled with rocks placed a the cliff based to provide support and to absorb wave energy
- costs £50,000 per 100m
73
advantages/disadvantages of gabions?
advantages
- for the cost, they are good value for money as may last 20-25 years
- can become visually appealing if vegetated and looked after
disadvantages
- may only last 5-10 years before rusting
- seabirds may damage their feet in them
74
what is beach nourishment/reprofiling?
- the addition of sediment to the beach to make it wider and higher
- the sediment is usually obtained offshore locally so it blends in with existing beach material
- bulldozers shape the material once on the beach (re-profiling)
- although cheaper than hard engineering options, has high overheads and costs around £500,000 per 100m
75
advantages/disadvantages of beach nourishment/reprofiling?
advantages
- a wider beach means more room for beach users, attracting more tourists
- people living along the sea front are more protected from coastal flooding
- at sandbanks, the wider nourished beach protects expensive properties
disadvantages
- it does require constant maintenance (unless there are other structures built to retain the beach)
76
what is dune regeneration?
- sand dunes are effective natural coastal defenders but due to trampling, they are easily damaged, becoming ineffective
- marram grass is planted to help stabilise the dunes and allow them to develop further
- fences are then created to deter people from crossing over the dunes
- cost £200-£2000 per 100m
77
advantages/disadvantages of dune regeneration?
advantages
- relatively cheap
- they maintain the natural environment that is popular with people and wildlife
disadvantages
- planting the marram grass and fencing off the areas can be time consuming and then can be damaged by storms
- people don't always respond to the deterrent of the fenced off areas and continue to walk through
78
what is dune fencing?
- fences are constructed in front of the dunes along the seaward side (facing the sea) in order to encourage new dune formation
- these newly formed dunes help to protect the existing dunes
- they cost £400-£2000 per 100m
79
advantages/disadvantages of dune fencing?
advantages
- there is very minimal impact on the natural systems of the area
- they can control public access to protect other ecosystems
disadvantages
- can be somewhat unsightly, especially if they are broken
- require regular maintenance especially during stormy weather
80
what is managed retreat?
coastal management (a form of soft engineering)
- the deliberate policy of allowing the sea to flood or erode an area (often an area or low £ value)
81
what are some advantages of managed retreat?
- allow natural processes to take place = less intrusive than HE
- long-term = sustainable
- less expensive generally and with climate change, a quicker response (sustainable)
82
what is an example of managed retreat?
Medmerry Managed Retreat, near Chichester, West Sussex
- low-lying coastline- mainly used for farming and caravan parks
- previously protected by a low sea wall
- was in need of repair- would cost too much
- allowed the sea to breach current defences
- flood some farmland
Scheme: The Medmerry Scheme - £28 million
83
how is managed retreat sustainable/helping the future?
- creates a large salt marsh- natural buffer against the sea
- protection for the farmlands and caravan park
- encourage tourism- visitors to the area £££
- help establish a valuable wildlife habitat
84
what is a form of coastal monitoring and adaption?
the 'Do Nothing' approach
85
what does the 'Do Nothing' approach involve?
- when some low-lying lo-value land is not defended against the sea
- people in these areas are instead relocated further inland- an adaption e.g. moving a golf pole, a path, a holiday park or fence
- scientists conduct regular monitoring of the coastline = help balance between allowing the retreat vs safety of the locals; also seeing if the approach is the most appropriate
86
what does coastal monitoring involve?
- studying marine processes
- mass movement
- human activity
if conditions change; like risk of flooding threatening property, a new approach will be needed
87
where is swanage?
- swanage is a seaside town in Dorset
- south coast of England
- located in a sheltered bay and has a broad sandy beach
- many impressive landforms of coastal erosion and deposition
- different rock types are important in formation of this coastline
- rocks have been folded and tilted so that bands of different rock types reach the coast
- headlands and bays form where there are alternating bands of more resistant (harder) and less resistant (softer) rocks
88
what is the coastline like at swanage?
- indented coastline is called a discordant coastline
- on south coast, only one type of rock (limestone)
- forming relatively straight section and is called a concordant coastline
- to north of swanage is poole harbour, one of the uk's largest natural harbours
- great deal of deposition has taken place in this large, sheltered bay
89
examples of coastal landforms?
sand dunes = Studland
stack = Old Harry's Stack
arch = Durdle Door
wave-cut platform = the base of Old Harry's Stack
spit = Studland Spit
beaches = Swanage Beach
headland = Ballard Point and Durlston Head
cliff = Durlston Head
salt marsh = Behind Studland Spit
90
information on Lyme Regis?
- located on actively eroding stretch of West Dorset coast
- faces considerable challenges from coastal erosion and land-slipping
- problems particularly serious in last 100 years
- many properties getting destroyed or damaged
91
why has it been necessary to implement a scheme in Lyme Regis?
rate of coastal erosion has increased causing homes and businesses to be damaged
92
phase 1 of Lyme Regis scheme?
1990-1995
- involved construction of a sea wall and promenade to east of mouth of River Lim
- emergency cliff stabilisation project was completed during winter of 2003-2004 which involved using large nails to hold rocks together and improving drainage and reprofiling slope of beach
93
phase 2 of Lyme Regis scheme?
2005-2007
£22 million spent on extensive improvements to seafront, including:
- construction of new seawalls and promenades
- creation of a wide sand and shingle beach designed to absorb wave energy
- extension of rock armour to protect harbour wall (The Cobb) and o the eastern end of the seafront to absorb wave energy and retain the new beach
94
phase 3 of Lyme Regis scheme?
not undertaken
- plan to prevent landslips and coastal erosion to west of The Cobb
- cancelled as cost outweighed benefits and land behind low value so hard to justify cost
95
phase 4 of Lyme Regis scheme?
2013-2015
- construction offences to protect coast to east of town
- £20 million project involved building 390m sea wall in front of existing wall
- 480 homes protected as cliffs stabilised by nailing, piling and improving drainage
- nails, up to 19 metres long, have been installed into the cliffs; once installed, nails were covered with a 60 to 120 year design life mesh
96
advantages of Lyme Regis scheme?
- there has been significant improvement in attractiveness of seafront and beach due to nourishment and wide promenade
- increased visitor numbers
- thriving seafront businesses
- new defences have withstood recent stormy winters
- harbour is better protected, benefitting the fishing industry and boat owners
97
disadvantages of Lyme Regis scheme?
- conflicts increased as visitor numbers increased e.g. local people experienced increased traffic congestion and litter due to increased tourism
- some feel the new coastal defences have spoilt the natural coastal landscape
- new defences may interfere with natural coastal processes affecting neighbouring stretches of coastline, causing conflicts elsewhere
- stabilising cliffs that prevent landslides will reduce number of fossils found in area
98
what are the three sections of a river?
upper course, middle course and lower course
99
what are some features of the upper course of a river?
- steep gradient
- v-shaped valley
- steep sides
- narrow, shallow channel
- vertical erosion
100
what are some features of the middle course of a river?
- medium gradient
- gently sloping valley sides
- wider, deeper channel
- lateral erosion
101
what are some features of the lower course of a river?
- gentle gradient
- very wide, almost flat valley
- very wide, deep channel
102
what is a tributary?
a small stream that joins a larger river
103
what is a drainage basin?
an area of land drained by a river and it's tributaries
104
what is a source?
the start of a river
105
what is a mouth?
the end of a river, usually where a river joins the sea
106
what is a watershed?
the edge of a river basin
107
what is a confluence?
where a tributary joins a larger river
108
what are the 4 erosion processes that occur in rivers?
1. hydraulic action
2. abrasion
3. attrition
4. solution
109
what happens during hydraulic action in rivers?
(erosion)
- this is where sheer force of fast-flowing water hits river banks and river beds and forces water into cracks
- this compresses air in cracks
- repeated changes in air pressure weaken the channel
- this is responsible for vertical erosion in upper course of a river
- in lower course, it contributes to lateral erosion of banks, especially when fast flowing water hits outside bend of meander
110
what happens during abrasion in rivers?
(erosion)
- also called corrasion
- small boulders and stones may scratch and scrape their way down a river during transport, thereby wearing down river banks and bed
- stones which have fallen into channel quite recently will be angular and have sharp, jagged edges
- these are particularly effective tools of this type of erosion as this is responsible for both vertical and lateral erosion
111
what happens during attrition in rivers?
(erosion)
- this affects a river's load
- when stones first enter a river, they will be jagged and angular
- as they are transported downstream, stones collide with each other and also with the river banks and bed
- this gradually knocks off the stones jagged edges so they become smooth and more rounded
- some collisions may cause a stone to be smashed into several smaller pieces
- these re-sized stones will be further smoothed and rounded on their journey to the sea
112
what happens during solution in rivers?
(erosion)
- this fluvial process is also known as corrosion
- refers to dissolving of rocks such as chalk and limestone
- rivers travelling over chalk and limestone will erode them this way by causing a chemical reaction, which dissolves the rocks and therefore eroding them
113
what are the 4 transportation processes that occur in rivers?
1. traction
2. saltation
3. suspension
4. solution
114
what happens during traction in rivers?
(transportation)
- this process moves large boulders and rocks along the river bed
- material is too large to be carried by the current of the river, therefore it is rolled along the river bed
- load carried in this way called the bed load
115
what happens during saltation in rivers?
(transportation)
- with this transportation process, small pebbles and stones are bounced along the river bed
- the load is alternately lifted then dropped in line with a local rise and fall in the velocity of the water
- essentially the particles are too large to be suspended by the river, however not large enough to be dragged along as part of the bed load
116
what happens during suspension in rivers?
(transportation)
- what happens to finer material (silt)
- fine particles such as alluvium are held up and carried within the rivers flow because they are light
- fine material carried in this way is called the suspended load
117
what happens during solution in rivers?
(transportation)
- also known as corrosion
- refers to dissolving of rocks like chalk
- chemical change affecting rocks such as limestone and chalk
- load to be transported in this way is called the solute load
118
what other process occurs in rivers (besides erosion/transportation processes)?
deposition
119
what happens during deposition in rivers?
- deposition is the process by which a river drops its load
- material deposited by a river is called sediment
- the bigger the load particle, the greater the velocity needed to keep it moving
- when velocity falls, large boulders are therefore the first to be deposited
- the finest particles are deposited last
- this explains why mountain streams have boulders along their bed, while close to a river's mouth there is only fine silt
- along it's course a river will deposit it's load wherever the velocity falls
- this could be at the base of a waterfall, on the inside of a meander, or where the river enters the sea of lake
120
describe an interlocking spur; how are they formed?
- projections of high land that alternate from either side of a v-shaped valley
- formed by fluvial erosion and found in upper course of river where rocks are hard
- river not powerful enough to cut through spurs of land and so has to flow around them
121
what is a waterfall and how is it formed?
- waterfall is a sudden drop along the river course
- forms when there are horizontal bands of resistant rock (hard rock) positioned over exposed, less resistant rock (soft rock)
122
explain the formation of a waterfall
1. the soft rock is eroded quicker than the hard rock, creating a step
2. as erosion continues, hard rock is undercut forming an overhang
3. abrasion and hydraulic action erode to create a plunge pool
4. over time this gets bigger, increasing the size of the overhang until the hard rock is no longer supported and it collapses
5. this process continues and the waterfall retreats upstream
6. a steep-sided valley is left where the waterfall once was; this is called a gorge
123
what is a gorge?
- a vertical, narrow, steep-sided valley that is usually found immediately downstream of a waterfall
- formed by the gradual retreat of waterfalls over hundreds/thousands of years
124
what are riffles?
a shallow bed
125
what are pools?
a deeper part of the river bed
126
what is helicoidal flow?
the corkscrew movement of the water and its sediment
127
what is a slip-off slope?
sand and pebbles are deposited on the inside bank
128
what is a river cliff?
on the outside of the bank, abrasion and hydraulic action form a river cliff
129
what is a thalweg?
line of fastest flow
130
what does it mean if a river is sinuous?
a river with many meanders
131
what is a meander?
a meander is a bend in a river, found mainly in lowland areas and are extremely common in the middle course of a river
132
explain the formation of a meander
- fast flowing water on the outside of the bank causes lateral erosion through abrasion and hydraulic action, which undercuts the banks and forms a river cliff
- helicoidal flow is a corkscrew movement; the top part of the flow hits the outside of the bank and erodes it
- the flow then 'corkscrews' down to the next inside bend where it deposits its load due to friction slowing down the flow
- fast flow causes vertical erosion on the outside bend, this deepens the river bed, resulting in an asymmetrical cross-profile
- sand and pebbles are deposited on the inside bank where the current is slower, forming a gentle slip-off slope
133
how is an ox bow lake formed?
- a river with many meanders is called a sinuous river
- loops increase in size as erosion continues on outside bank and deposition continues on inside bank
- as meanders grow, they migrate over the floodplain
- as they migrate, they may start to erode towards each other
- gradually, the neck of the meander narrows until it is completely broken through (usually during a flood) to form a new straighter channel
- the old meander loop is cut off by deposition from subsequent flooding to form an ox-bow lake
134
know your bends!
outside = ?
inside = ?
outside = erosion (Eat Out)
inside = deposition (Dine In)
135
how are levees formed?
- when a river bursts its banks, friction with the land reduces velocity and causes deposition
- heavy sediment is deposited closest to the river
- the size of sediment then becomes progressively smaller with distance from the river
- with each successive flood, the banks are built up higher
- although it may seem this would make it harder for river to flood next time, this is not the case as over time the bed of the river deposits a thicker layer of sediment, which raises the river in its channel
136
explain the 2 processes that form flood plains
1.
- meanders migrate across the flood plain due to lateral erosion
- when they reach the edge of the floodplain, they erode the valley side
- eventually, this cuts a wider valley
2.
- when the river floods it deposits silt, creating a very flat flood plain
- layer upon layer builds up over many years, forming a thick deposit of fertile alluvium
137
what is an estuary?
- estuaries are found at the mouth of a river, in it's lower course, where the river meets the sea
- the water here is tidal, the river level rises and falls each day
- during rising tide, velocity falls, sediment deposited
- at low tide, fine deposits form mudflats which develop. into salt marshes over time which are important natural habitats
138
information about the source of the River Tees
- source is high up in Pennines (893m)
- close to Cross Fell at Tees Head
- from there it flows roughly east for around 128km to reach North Sea at Middlesborough
139
information about the high force waterfall in the upper course of the River Tees
- high force waterfall in upper course of River Tees close to Forest-in-Teesdale
- has 20m drop into turbulent plunge pool
- impressive gorge runs approx 700m
- consists of resistant whinstone (dolerite) rock overlying weaker carboniferous limestone
140
information about the meanders in the middle course of the River Tees
- River Tees becomes less steep as it enters middle course and meanders develop with increased lateral erosion
- River Tees meanders it's way through lower gradient past Barnard Castle
141
information about the ox bow lakes in the middle/lower course of the River Tees
- a sweeping meander at Sockburn (near Darlington) will eventually develop into ox bow lake as neck of meander becomes narrower
142
information about the levees in the lower course of the River Lees
- flooding has caused the development of raised banks (levees) along lower course
- e.g. near Neasham
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information about the Tees Estuary in the lower course of the River Tees
- wide with mudflats and sandbanks
- formed by sea-level rise at end of last ice age
- parts of the estuary important for wildlife and have become SSSIs (sites of special scientific interest)
- iron and steel engineering/chemical works have developed along the estuary
144
information about the mouth of the River Tees
- the River Tees flows roughly east from the source for around 128km to reach the North Sea at Middlesborough
145
what factors affect flood risk?
- deforestation
- precipitation
- relief
- agriculture
- geology
- urbanisation
146
is deforestation a physical or human factor affecting flood risk?
human
147
is precipitation a physical or human factor affecting food risk?
physical
148
is relief a physical or human factor affecting flood risk?
physical
149
is agriculture a physical or human factor affecting flood risk?
human
150
is geology a physical or human factor affecting flood risk?
physical
151
is urbanisation a physical or human factor affecting flood risk?
human
152
describe what happens during precipitation (affecting flood risk)
- torrential rainstorms or prolonged rainfall can lead to flash floods
- steady rainfall over several days can lead to flooding in lowland river basins
152
describe what happens during deforestation (affecting flood risk)
- trees are removed
- more water suddenly available and transferred rapidly to river channels (increasing flood risk)
153
describe what happens during relief (affecting flood risk)
- in highland environments steep slopes encourage rapid transfer of water towards river channels
- valley floor with steep sides at higher risk of flooding
153
describe what happens during agriculture (affecting flood risk)
- in arable farming, soil left unused and exposed to elements for periods of time
- can lead to more surface runoff
154
describe what happens during geology (affecting flood risk)
- impermeable rocks like granite, shales and clays encourage water to flow overland (runoff) and into river channels
155
describe what happens during urbanisation (affecting flood risk)
- building on floodplains creates impermeable surfaces like tarmac roads, concrete driveways and slate
156
explain why deforestation affects flood risk
- much of the water that falls on trees is evaporated or stored temporarily on leaves and branches
- trees use water as they grow
- removal of trees means this water will flow to river channels
157
explain why precipitation affects flood risk
- river channels cannot contain sheer volume of water flowing into them
158
explain why relief affects flood risk
- steep slopes mean surface runoff occurs on mountain sides before rain has had time to infiltrate soils
159
explain why agriculture affects flood risk
- water can flow quickly along furrows as land is ploughed up and down steep slopes
160
explain why geology affects flood risk
- increases river discharge (amount of water in a river) and makes flooding more likely
161
explain why urbanisation affects flood risk
- increases surface runoff and water is transferred quickly to drains and sewers then into river channels
162
what is a hydrograph and what does it show?
- the volume of water flowing along a river is its discharge
- it is measured in cumecs (cubic metres per second)
- hydrographs plot river discharge after a storm
- shows how discharge rises during a storm, reaches its peak and them returns to normal rate of flow
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what is the shape of a hydrograph affected by?
rainfall and drainage basin characteristics
164
what does it mean if a hydrograph is flashy?
steep rising limb with short lag time
165
what are some drainage basin and precipitation characteristics?
- basin size
- drainage density
- rock type
- land use
- relief
- soil moisture
- rainfall intensity
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how could basin size lead to a flashy hydrograph?
small basins often lead to a rapid water transfer
167
how could basin size lead to a low, flat hydrograph?
large basins result in a relatively slow water transfer
168
how could drainage density lead to a flashy hydrograph?
a high density speeds up water transfer
169
how could drainage density lead to a low, flat hydrograph?
a low density leads to a slower transfer
170
how could rock type lead to a flashy hydrograph?
impermeable rocks encourage rapid overland flow
171
how could rock type lead to a low, flat hydrograph?
permeable rocks encourage a slow transfer by groundwater flow
172
how could land use lead to a flashy hydrograph?
urbanisation encourages rapid water transfer
173
how could land use lead to a low, flat hydrograph?
forests slow down water transfer, because of interception
174
how could relief lead to a flashy hydrograph?
steep slopes lead to rapid water transfer
175
how could relief lead to a low, flat hydrograph?
gentle slopes slow down water transfer
176
how could soil moisture lead to a flashy hydrograph?
saturated soil results in rapid overland flow
177
how could soil moisture lead to a low, flat hydrograph?
dry soil soaks up water and slows down its transfer
178
how could rainfall intensity lead to a flashy hydrograph?
heavy rain may exceed the infiltration capacity of vegetation, and lead to rapid overland flow
179
how could rainfall intensity lead to a low, flat hydrograph?
light rain will transfer slowly and most will soak into the soil
180
what is the preferred option for managing floods and protecting expensive property or land?
hard engineering
181
what are some hard engineering strategies for managing floods?
- dams and reservoirs
- channel straightening
- embankments
- flood relief channels
182
what are dams and reservoirs?
dams are large concrete barriers built across a river to impede it's flow; the water behind the dam is stored in an artificial lake called a reservoir
- this restricts the supply of water downstream
- water is then gradually released downstream to control flow of water and reduce flood risk
183
what is channel straightening?
involves cutting through meanders and creating a wider, deeper and straighter channel to speed flow of water (sometimes concrete land)
- aim to help to improve navigation and reduce flooding
184
what are embankments?
artificially raised banks, increasing channel capacity to reduce flood risk
- bulldozers used to build up height of banks with impermeable soil (sometimes lined with concrete)
185
what are flood relief channels?
an artificially constructed channel designed to be a back up for rivers that frequently flood, bypassing major urban areas
- at high flow, sluice gates are opened, allowing excess water to flow into relief channel, reducing flooding threat
186
what are the economic, environmental and social benefits of dams and reservoirs?
economic:
- boosts tourism; e.g. Kielder dam attracts 300K tourists a year, boosting local economy by £6m
environmental:
- forestry; over 150m trees planted at Kielder, providing source of employment
social:
- highly effective against flooding; highly controlled release of water, virtually no risk
187
what are the economic, environmental and social costs of dams and reservoirs?
economic:
- expensive; Kielder cost £167m (expensive to build and high maintenance costs)
environmental:
- concrete dams interrupt path of migrating fish
social:
- flooding of valley displaces people, mainly farmers; causing stress and breaks up communities e.g. Kielder = 58 families displaced
188
what are the economic and social benefits of channel straightening?
economic:
- historic cuts on River Tees reduced length of river by 4.4km
- straightened course improved navigation and increased trade at Stockton's port
social:
- straightened river reduces flood risk by moving water out of area faster as less friction with bed/banks
- faster flowing water also removes sediment that would otherwise build up height of river bed
189
what are the economic, environmental and social costs of channel straightening?
economic:
- expensive
- dredging to remove silt further downstream is costly
environmental:
- flooding caused downstream can destroy habitats
social:
- when water meets meander further downstream, velocity is reduced
- sedimentation/deposition results, building up river bed and increasing chance of flooding there
190
what are the economic, environmental and social benefits of embankments?
economic:
- cheaper than other methods of hard engineering
environmental:
- earthen embankments provide new habitats for animals like voles and others
social:
- less chance of flooding as channel has increased capacity for higher discharge
- settlements behind raised banks protected
190
what are the economic, environmental and social costs of embankments?
economic:
- high maintenance costs (constant monitoring/repair)
environmental:
- if breached, water lies on land for long time as it's route back to river restricted
social:
- not as reliable as other types of HE
- giving people false sense of security and means they may not be prepared for possible flooding
191
what are the economic, environmental and social benefits of flood relief channels?
economic:
- insurance costs reduced
environmental:
- some channels include artificial reed beds, providing new habitats
social:
- calm water provides areas for canoeing
192
what are the economic, environmental and social costs of flood relief channels?
economic:
- take a long time to complete e.g. Exeter's relief channel took 12 years
environmental:
- unattractive to landscape during low flow when vast amounts of concrete and gaboon's are exposed
social:
- displaced people who live in path of channels, causing disruption
193
what are some soft engineering strategies for managing floods?
- flood plain zoning
- planting trees
- flood warnings and preparations
- river restoration
194
what is flood plain zoning?
- the Environmental Agency categorises floodplains into 4 flood risk zones
- restricting land use on different parts of food plain
- land used in way that minimises impact of flooding, depending on how at risk an area is
- low cost land-use areas like playing fields are closer to rivers vs high cost factories and housing are built further away
195
how does planting trees help manage flooding?
- by planting trees across slopes and on floodplains, reduces flood risk due to increased interception of water by trees and water taken up by roots
196
how do flood warnings and preparation work?
- the Environmental Agency, councils etc co-ordinate action plans for areas at risk
- MET office provides data to EA; use it along with river level data and flood maps published on websites
- flood alert information is sent through media along with info on flood prep
197
how does river restoration work?
- rivers that were hard engineered are restored to natural channels, including recreation of meanders and lowering floodplains
- e.g. River Quaggy (Greenwich)- had been re-routed in underground drains but has now been returned to it's old course on the surface
198
what are the social, economic ad environmental benefits of flood plain zoning?
social:
- having less impermeable surfaces due to restricted building on flood plain will reduce risk of flooding
economic:
- low cost; only administration costs
environmental:
- conserved floodplains provide welcome greenspace in UK towns
199
what are the social, economic and environmental costs of flood plain zoning?
200
social:
- limited impact in UK as many cities have already sprawled across floodplain
economic:
- housing shortage in UK; restricting building worsens problem and inflates existing house prices
environmental:
- habitats destroyed due to increased building on other greenfield sites
201
what are the economic and environmental benefits of planting trees?
economic:
- relatively inexpensive as EU grants available
environmental:
- creating shelter belts across slopes and woodlands means that less water is able to reach the channel as the leaves intercept and store the water and some water is taken up by roots
- more carbon dioxide absorbed
202
what are the social and environmental costs of planting trees?
social:
- changed appearance; countryside wooded rather than open grass; arguably artificial looking/less aesthetically pleasing
environmental:
- loss of potential grazing land
203
what are the social and economic benefits of flood warnings and preparation?
social:
- advanced warning means people have time to protect their property and valuables earlier
- ensures peoples' safety without investing in expensive HE
economic:
- cheap method, just dependent on online communication alone
204
what are the social and economic costs of flood warnings and preparation?
social:
- only effective if people listen and take action
- not everyone listens or has access to internet
- possibility of loss/flooding of agricultural land near river
economic:
- doesn't help those in flood, prone areas
- people may need to move to temp. accommodation
- insurance costs increase
- difficult to sell property
205
what are the social, economic and environmental benefits of river restoration?
social:
- aesthetically pleasing e.g. visitor numbers to Sutcliffe Park have increased
economic:
- increased water storage areas reduce risk further downstream e.g. River Quaggy scheme has protected 600 homes and businesses from flooding
environmental:
- creates new wetland habitats, increasing biodiversity
206
what are the social, economic and environmental costs of river restoration?
social:
- not always the most effective or practical strategy
economic:
- can be expensive (River Quaggy restoration £11m)
environmental:
- possibility of loss/flooding of agricultural land near river
