UK River Landscapes Flashcards
(86 cards)
1
Q
What’s a Course (in river)?
A
Path of river as it flows downhill
2
Q
Where is the Upper Course of the river?
A
Closest to the source of the river
3
Q
Where is the Lower Source of the river?
A
Closest to the mouth of the river
4
Q
As rivers flow downhill what do they form?
A
- Form channels and valleys
- Erode landscape, material is deposited
- Shape of valley & channel changes along river depending on if erosion had the most impact
5
Q
What does the Long Profile of a river show you?
A
How gradient (steepness) changes over different courses
6
Q
What does the Cross Profile of a river show you?
A
What a cross section of the river looks like
7
Q
What is the Gradient and Valley and Channel Shape at the Upper Course?
A
- Steep gradient
* V-shaped valley, steep sides, narrow, shallow channel
8
Q
What is the Gradient and Valley and Channel Shape at the Middle Course?
A
- Medium gradient
* Gently sloping valley sides, wider, deeper channel
9
Q
What is the Gradient and Valley and Channel Shape at the Lower Course?
A
- Gentle gradient
* Very wise, almost flat valley, very wide, deep channel
10
Q
What is Vertical Erosion?
A
- Deepens river valley= v-shaped
- Dominant in upper course
- High turbulence = rough particles against river bed = intense downwards erosion
11
Q
What is Lateral Erosion?
A
- Widens river valley during formation of meanders
* Dominant in middle & lower courses
12
Q
What’s does Weathering do?
A
Breaks down rocks on the valley sides
13
Q
What is Freeze-thaw weathering and when does it happen?
A
•Happens at freezing point of water
•Water into rock with cracks
•Water freezes it expands =
pressure on rock
•Water thaws it contracts = releases pressure on rock
•Repeating this widens crack & rock breaks
14
Q
What are the Processes of Erosion?
A
- Hydraulic Action
- Abrasion
- Attrition
- Solution
15
Q
What is Hydraulic Action?
A
Force of water breaks rock particles away from river channel
16
Q
What is Solution?
A
River water dissolves some types of rock (chalk, limestone)
17
Q
What is Abrasion?
A
Eroded rocks picked up by river scrape, rub again channel, wearing it away
18
Q
What is Attrition?
A
- Eroded rocks picked up by river smash together breaking into smaller fragments
- Causes particle size to decrease between rivers source & mouth
19
Q
What is Transportation?
A
Movement of eroded material
20
Q
What are the Processes of Transportation?
A
- Traction
- Suspension
- Saltation
- Solution
21
Q
What is Traction?
A
Large particles (boulders) pushed along river bed by force of water
22
Q
What is Suspension?
A
Small particles (clay,silt) carried along by water
23
Q
What is Saltation?
A
Pebble-sized particles bounced along river bed by force of water
24
Q
What is Solution?
A
Soluble materials dissolve in water, carried along
25
What is Deposition?
* River drops eroded material it’s transporting
| * Happens when river slows down
26
Why do rivers Slow down and Deposit material?
* Volume of water in river falls
* Eroded material increases
* Water shallower
* River reaches its mouth
27
Where do Waterfalls and Gorges form?
Upper course of river
28
How is a Waterfall formed?
* Softer rock eroded by abrasion more than hard rock = ‘step’
* Water goes over step, erodes soft rock more
* Steep drop created = waterfall
29
How is a Plunge Pool formed?
* Hard rock undercut by erosion, now unsupported & collapses
* Swirled around at foot of waterfall, erode soft rock by abrasion = plunge pool
30
How is a Gorge formed?
* More undercutting = more collapses
| * Waterfall retreats = gorge
31
How are Interlocking Spurs formed?
* Erosion is downwards = v-shaped valleys
* Rivers wind around hillsides
* Hillsides that interlock as river wind around them = interlocking spurs
32
What are Meanders?
Large bends in a river
33
How are River Cliffs formed?
* Current faster on outside of bend, river channel is deeper
* More erosion takes place on outside of bend = river cliff
34
How are Slip-Off Slopes formed?
* Current slower on inside of bend, river channel is shallower
* Eroded material deposited on inside of bend = slip-off slopes
35
How are Ox-Bow Lakes formed?
* Erosion causes outside bends to get closer
* Only small bit of land left between bends
* River breaks through land
* River flows along shortest course
* Deposition cuts off meander
* Ox-bow lake formed
36
What are Flood Plains?
Wide valley floors on either side of a river, regularly floods
37
How do Flood Plains form into its Structure?
* Flood = water slow down & deposits eroded material = building up flood plain
* Meanders migrate across flood plain = wider
* Meanders migrate downstream = flattening our valley floor
38
What are Levees?
Natural embankments along edges of river channel
39
How are Levees formed?
* Eroded material deposited during flood over flood plain
* Heaviest material deposited closest to channel
* Deposited material builds up = levees
40
How are Deltas formed?
* Rivers slow down when at sea
* Deposit material it’s carrying
* Material builds up, channel blocked
* Channel split into smaller rivers
* Material builds up a lot, low lying areas of land (Deltas) formed
41
What are Distributaries?
Channel splits into lots of smaller rivers
42
What are Estuaries?
Tidal mouth of river, tide meats sea/stream
43
How are Mudflats formed?
* Water floods over banks, carrying silt&sand on valley floor
* Water move slowly as tide reaches highest point, sediment deposited
* More mud builds up = mudflats
44
What is River Discharge?
Volume of water that flows in river per second
45
What is Peak Discharge?
Highest discharge in period of time your looking at
46
What is Lag Time?
Delay between peak rainfall & peak discharge
47
What is Rising Limb?
Increase in river discharge as rainwater flows into river
48
What is Falling Limb?
Decrease in river discharge as river returns to normal level
49
Why does Flooding Happen?
Level of river gets so high it spills over its banks
50
How does Prolonged Rainfall cause Flooding?
* Long period of rain
* Soil saturated
* Further rainfall can’t infiltrate
* Increased runoff into rivers
* Discharge Increases
* Flooding more likely
51
How does Heavy Rainfall cause Flooding?
* Water too quick for infiltration
* A lot of runoff
* Discharge Increases
* Flooding more likely
52
How does Geology (rock type) cause Flooding?
* Clay soils & some rocks impermeable
* Runoff Increases
* Discharge increases quickly
* Flooding more likely
53
How does Relief cause Flooding?
* Steep-sided valley, water reach channel faster
* Discharge increases quickly
* Flooding more likely
54
How does Land use cause Flooding?
```
•Buildings made from impermeable materials
•Increase runoff
•Discharge increases quickly
•Flooding more likely
And
•Cutting down trees increase volume of water that reaches river channel
•Increases Discharge
•Flooding more likely
```
55
What is Hard Engineering?
Man-made structures built to control flow of rivers and reduce flooding
56
What are Hard Engineering Methods?
* Dams and Reservoirs
* Channel Straightening
* Embankments/Flood Walls
* Flood Relief Channels
57
What are Dams?
Huge walls built across rivers, in the upper course
58
What is a Reservoir?
Artificial lake formed behind the dam
59
What is Channel Straightening?
River course straightened - Meanders cut out by building artificial straight channels
60
What are Embankments/Flood Walls?
Raised walls built along river banks
61
What are Flood Relief Channels?
Channels built to divert water to important areas or elsewhere if water level too high
62
What are the Benefits of Dams and Reservoirs?
* Store water - reduce flooding
| * Water used as drinking water & generate hydroelectric power
63
What are the Disadvantages of Dams and Reservoirs?
* Dams expensive
* Reservoir can flood existing settlement
* Farmland become less fertile
64
What are the Benefits of Channel Straightening?
Water out of area quickly because doesn’t travel far - reduce flooding
65
What are the Disadvantages of Channel Straightening?
* Flooding happen downstream, as water there faster
| * Erosion downstream because fast flowing water
66
What are the Benefits of Embankments/Flood Walls?
River hold more water - flood less frequently
67
What are the Disadvantages of Embankments/Flood Walls?
* Expensive
| * Risk of severe flooding if water rise above embankment
68
What are the Benefits of Flood Relief Channels?
* River discharge reduced - flooding reduced
| * Water controlled by gates on flood relief channels
69
What are the Disadvantages of Flood Relief Channels?
* Increase discharge where relief channel rejoins river = flooding
* Water level too high for channels = flood
70
What is Soft Engineering?
Schemes set up using knowledge of river & its processes to reduce effects of flooding
71
What are Soft Engineering Methods?
* Flood Warnings
* Preparation
* Flood plain zoning
* Planting Trees
* River restoration
72
What are Flood Warnings?
Environment agency warn people about flooding through TV, radio, internet, etc
73
How does Preparation reduce effect of flooding?
* Buildings modified to reduce damage a flood could cause
| * People make plans for what to do in a flood
74
How does Flood Plain Zoning reduce effect of flooding?
Restrictions prevent building on parts of flood plain likely to be affected by a flood
75
How does Planting Trees reduce effect of flooding?
Increases interception of rainwater, increases lag time
76
What is River Restoration?
Making river more natural
77
What are the Benefits of Flood Warnings?
* Impact of flooding reduced
| * Give people time to prepare
78
What are the Disadvantages of Flood Warnings?
* Don’t stop a flood from happening
| * People might not have access to or hear the warning
79
What are the Advantages of Preparation?
* Impact of flooding reduced
* People worry less about threat
* People know what to do
* Buildings less damaged
80
What are the Disadvantages of Preparation?
* Doesn’t guarantee safer from flood
* Gives people false sense of security
* Expensive to modify homes
81
What are the Benefits of Flood Plain Zoning?
* Risk of flooding reduced - impermeable surfaces aren’t created
* Impact of flooding reduced - no buildings to damage
82
What are the Disadvantages of Flood Plain Zoning?
Expansion of urban area limited if no other building sites
83
What are the Benefits of Planting Trees?
* Discharge & flood risk reduced
* Vegetation reduces soil erosion
* Provides habitats for wildlife
84
What are the Disadvantages of Planting Trees?
Less land available for farming
85
What are the Benefits of River Restoration?
* Less risk of flooding downstream, discharge reduced
* Little maintenance needed
* Better habitats for wildlife
86
What are the Disadvantages of River Restoration?
Local flood risk can increase
