River Landscapes in the UK Flashcards
1
Q
What is a river
A
A ribbon-like body of water that flows downhill from the force of gravity
2
Q
What is the source
A
Where the river starts
3
Q
What is the mouth
A
Where the river ends
4
Q
What is the tributary
A
Stream or smaller river meeting the main channel
5
Q
What is the confluence
A
Area where the tributary meets the main channel
6
Q
What is the drainage basin
A
Area of land drained by a river
7
Q
What is the watershed
A
The dividing line formed by hills that marks a boundary between two drainage basins
8
Q
What is a river long profile
A
The gradient of a river as it journeys from source to mouth
9
Q
What are the 3 sections of a river
A
Upper Course
Middle Course
Lower Course
10
Q
What are the two types of erosion
A
Lateral
Vertical
11
Q
What is vertical erosion
A
Deepening of a riverbed, mostly by hydraulic action. It is dominant in the upper course of a river. The little energy provided, deepens the chance
12
Q
What is lateral erosion
A
“Sideways” erosion. It wears away the banks of a river. It is dominant in the lower course of a river
13
Q
Give some characteristics of the Upper Course
A
Steep gradients
Narrow river channels
Interlocking spurs
Steep valley sides
Vertical erosion
14
Q
Give landforms in the Upper Course
A
Waterfalls
Gorges
Interlocking spurs
Rapids
V Shaped Valleys
Steep valley sides
15
Q
What erosion applies in Upper Course
A
Vertical erosion
16
Q
What is a waterfall
A
A steep drop in the upper course of a river
17
Q
What is a gorge
A
A narrow steep sided valley forming after a retreated waterfall
18
Q
What is retreat
A
Backward action
19
Q
What is a plunge pool
A
A deep pool of water under a waterfall, created by falling water, rocks and other sediment
20
Q
What is overhang
A
A ledge of unsupported rock which eventually collapses
21
Q
What is undercutting
A
When land erodes at sea or river level, leaving unstable unsupported land above it
22
Q
What is headward erosion
A
Increases river length. It is the most active in the source area of a river or a steep riverbed
23
Q
How is a waterfall formed
A
- A band of hard rock is placed on top of a band of soft rock.
- Erosion processes such as abrasion and hydraulic action dominate as the river flows downstream
- Softer rock is eroded further than hard rock, which then forms a step in the riverbed
- The step then starts to undercut the hard rock, leaving an overhang, which then collapses, and falling rocks fall
- Fallen rocks form a plunge pool at the base of the waterfall, where the river continues to erode the softer rock. Dropped material is collected by the plunge pool via hydraulic action and abrasion
This all leaves a waterfall
24
Q
How is a gorge formed
A
When a waterfall retreats up a valley
25
What are interlocking spurs
Outcrops of land along a river course in the valley
26
How are interlocking spurs formed
1. Hydraulic action deepens the river channel
2. Freeze thaw weathering weakens the rock, giving the valley steep sides
3. River winds around projections of harder rock, taking the path of least resistance.
This leaves interlocking spurs
27
What is a V Shaped Valley
A steep sided valley
28
What is a meander
A river bend in the channel
29
What is an ox bow lake
When a meander is cut off to form a lake
30
What are landforms in the middle course
Meanders
Ox bow lakes
31
What erosion is used in the middle course
Lateral erosion
32
What are characteristics of the middle course
A gentle gradient and more lateral erosion than in upper course
A deeper and wider river channel
Tributaries
River beaches
33
How is a meander formed
1. When water makes its way to the middle course, it gains water and energy
2. Lateral erosion widens the river. When the water flows over flatter land, they develop large bends
This forms a meander
34
How are slip off slopes formed
1. As the river goes around a bend, most of the water is pushed outside. This increases speed and erosion (hydraulic action and abrasion)
2. Lateral erosion on the outside bend causes undercutting of the bank, forming a river cliff.
5. Water on the inside of the bend is slower, causing decreased water speed, and deposited eroded material, creating a gentle slope of sand and shingle
This forms a slip off slope
35
How is an ox bow lake formed
1. As erosion on the outside of bends continue, the river's bends get nearer to each other and create a swan's neck meander (a small piece of land between bends)
2. During floods, high energy water will breach the meander neck
3. This makes the river flow in a straighter and faster course
4. Overtime, deposits fill in the inside of bends
5. The meander is then cut off
This forms an oxbow lake
36
What are landforms in the lower course
Floodplains
Levees
Estuaries
Delta
37
What are characteristics in the lower course
Gentle flow on gentle slope
High volume
Large discharge of water
Low energy levels
Slow current
More lateral erosion
Wide and deep channel
Wide floodplain
38
What is a floodplain
An area of land covered in water when a river bursts its banks
39
How are floodplains formed
1. Erosion widens the valley away, removing the interlocking spurs present from the source and creating a wide, flat area next to the river
2. Lateral erosion occurs as a form of meander formation and meander migration
3. When the river overflows during a flood, material carried by the river is dropped as speed/energy is lost
4. Overtime, sediment forms layers on the floodplain
40
What is a levee
An embankment built to prevent the overflow of a river
41
How are levees often created
Floods. After lots of floods are created, lots of levees are formed
42
What is an estuary
The point where a river and sea meet. When they combine, they create brackish water
43
What happens to an estuary at low tide
The sea retreats and mudflats are exposed to air
44
What happens to an estuary at high tide
River overflows and sediments are built over time to make mudflats. River overflows its banks
45
What is a mudflat
A stretch of muddy land left uncovered at low tide.
46
What is river discharge
Volume of water flowing in river per second. It is measured in cubic metres per second
m cubed per second
47
What happens if we increase river discharge
River level is increased
48
Why does discharge and river velocity increase downstream
Discharge increases downstream as tributary streams join the main river and add their volume of water to it
49
How does a flood occur
When the amount of water in a river exceeds its capacity
50
What is capacity
A limited amount of something
51
How can we measure river discharge
Hydrographs
52
What is rainfall
When rain falls
53
What is peak rainfall
Maximum rainfall in a time period
54
What is lag time
Interval between peak discharge and peak rainfall
55
What is the rising limb
When discharge rises
56
What is falling limb
When discharge falls
57
What is hard engineering
Use of man made structures to prevent or control natural processes from taking place.
58
DRAWBACKS of hard engineering
Flood defences are too expensive
59
BENEFITS of hard engineering
Very efficient
Good protection
60
What are the four types of hard engineering river defences
Embankments
Channel straightening
Dredging
Dams
61
What are dams + reservoirs
An area of land which is required to be flooded to work
62
What are the drawbacks of dams + reservoirs
Involves displacing people
Distress, breakup communities
High costs
Soils downstream are less fertile from lack of river sediment deposited during floods
Fish migration disruption
Trapped sediment results in decreased reservoir capacity
Can trigger earthquakes
Creates landslides
Flood outstanding areas
63
What are the benefits of dams + reservoirs
Turbine dams provide renewable energy
Promote new habitats
Attractive looks
Good drinking supply
Very effective - good flood control
64
What is a flood relief channel
An artificial made channel designed as a backup channel for a frequently flooding river
65
What are the drawbacks of a flood relief channel
Southernmost people may face disruption
Settlements downstream suffer from increased flooding
Expensive costs
Long time length
66
What are the benefits of a flood relief channel
Removes risk of flooding from a designed area
Calm water provides a recreational area for model boating and canoeing
Attract artificial reed beds
Low insurance costs
67
What is dredging
The removal of sediments and rubbish from the bottom of the waterway
68
What are the drawbacks of dredging
Takes time to complete
River must be dredged regularly
Damage of natural habitats
Lowering oxygen levels
69
What are the benefits of dredging
Clean, healthy rivers
Prevents flooding by deepening and straightening the river channel
Restores harmed environments
70
What is an embankment
An artificially raised river bank (levee) Increases the water capacity of a river
71
What are the drawbacks of an embankment
Prescence gives people a false sense of security
High maintenance costs
Constant monitoring and repair is required
Unattractive looks
Increased downstream sediment provides a negative cost
72
What are the benefits of an embankment
Cheap costs
Safer from flooding - channel has an increased carrying capacity
Provides good walking routes
Attracts habitats
73
What is soft engineering
The process of working with natural processes to manage flood risk
74
What are the three types of soft engineering flood defences
River restoration
Wetlands
Floodplain zoning
75
What are wetlands
Areas that flooding is deliberately allowed to flood
76
What is river restoration
When the course of a river is artificially changed
77
What are flood warnings/precipitations
Warnings about floods
78
What are drawbacks of flood warnings
People may have restricted access to warnings
Flash floods may happen too quickly for an effective warming
They don't stop land from flooding - they just warn
79
What are benefits of flood warnings
People have time to protect properties
Many possessions can be saved
80
What is floodplain zoning
Restricts different land areas to access to the floodplain
81
What are drawbacks of floodplain zoning
Not always possible to change existing land uses
Planners need to decide what type of flood to plan for
82
