Physical Landscapes UK: River Landscapes and Processes Flashcards Preview

Geography > Physical Landscapes UK: River Landscapes and Processes > Flashcards

Flashcards in Physical Landscapes UK: River Landscapes and Processes Deck (63):
1

Hydrological cycle

Moves water between the land, sea and atomosphere:

1)Evaporation
2)Transpiration
3)Condensation
4)Precipitation
5)Surface flow
6)Infiltration
7)Through flow
8)Groundwater flow
9)Percolation
10)Interception

2

Transpiration

Water lost through leaves of plants.

3

Precipitation

Moisture falling from clouds as rain, snow or hail.

4

Surface runoff

Water flowing over surface of land into rivers.

5

Infiltration

Water absorbed into the soil from the ground.

6

Interception

Vegetation prevents water from reaching the ground.

7

Source

Start of a river.

8

Tributary

Smaller rivers that join to larger ones.

9

Confluence

Where 2 rivers join.

10

Mouth

End of a river, usually where a river joins the sea.

11

Watershed

Edge of river basin, usually highland.

12

Drainage basin

A catchment area for precipitation. Rain is drained by one river and its tributaries. Every river has a drainage basin.

13

Upper course features

When a river is near its SOURCE, it often develops V-SHAPED valleys as the river erodes DOWN (vertical erosion).
The GRADIENT here is STEEP and the river CHANNEL is NARROW.
VERTICAL erosion also causes the river to wind and bend to avoid areas of hard rock. This creates INTERLOCKING SPURS.
When a river runs over alternating layers of hard and soft rock, RAPIDS and WATERFALLS may form.

14

Formation of a waterfall:

When a river flows over different bands of rock:

1) Soft rock erodes more quickly, undercutting the hard rock.

2) Hard rock is left overhanging and because it isn’t supported, it eventually collapses.

3) Fallen rocks crash into the plunge pool at base of waterfall. They swirl around, causing more erosion.

4) Over time, this process is repeated and the waterfall moves upstream.
A steep-sided gorge is formed as the waterfall retreats.

15

Middle course features

In the middle course the river has MORE ENERGY and a HIGH VOLUME of water.
The GRADIENT here is GENTLE and LATERAL (sideways) EROSION has WIDENED the river CHANNEL.
The river channel has also DEEPENED. A larger river channel means there is LESS FRICTION, so the water FLOWS FASTER.
Lateral erosion causes the formation of MEANDERS and, eventually, OXBOW LAKES.

16

Oxbow lake

Over time, meanders start to erode towards each other.
Gradually the neck of the meander narrows until is is completely broken through to form a new straighter channel.
Water now takes the shortest route through the thalweg and deposition seals off the old meander, forming an oxbow lake.

17

Lower course features

In the lower course, the river has a HIGH VOLUME and a LARGE DISCHARGE.
The river CHANNEL is now DEEP and WIDE and the LANDSCAPE is FLAT. The river now has a wide FLOODPLAIN.
As a river reaches the end of its journey, ENERGY levels are LOW and DEPOSITION takes place. ESTUARIES are found at the mouth.

18

Meander

A bend in the river formed by lateral erosion + deposition.
Erosion + a river cliff are found on the outside of the bend. Water flows fastest (thalweg) there, where water flow has most energy due to decreased friction.
Deposition + a slip off slope are found on the inside of the bend, where there is more friction and water flow is slower.

19

Floodplain

A wide, flat area of marshy land on either side of the river that is covered in times of a flood. Found in middle and lower courses.
Made of alluvium, which is the sediment deposited during floods.
Floodplains are used for agriculture as alluvium is very fertile.
Formed when meanders reach end of floodplain due to lateral erosion, which widens the valley.

20

Levee

A raised riverbed formed by flooding over many years.
When a flood occurs, the river loses energy. The largest material is deposited first on the sides of the river banks and smaller material further away.
Water spreads the sediment out across the floodplain, building up the levee.
After many floods, the river bank is higher, so the channel can carry more water and flooding is less likely to occur in the future.

21

Estuary

Transitional zone between the river and the sea. The main process effecting estuaries is deposition.
During a rising tide river water can’t flow into the sea. The river's velocity falls and sediment is deposited.
At low tide these deposits form mudflats. Overtime, mudflats develop into important natural habitats called saltmarshes.

22

River case study: River Tees

Location and Background

Located in North of England and flows 137km from the Pennines to the North Sea

23

River case study: River Tees

Upper course

-Source high in the Pennine Hills
-High Force is UK’s largest waterfall at 21m high made from harder Whinstone and softer limestone rocks
-Plunge pool
-Gorges
-Rapids
-Vertical erosion has formed V-shaped valleys
-Rocks are smoothed as they move down the river by attrition
-Bed load of large rocks

24

River case study: River Tees

Middle course

-Lateral erosion has formed meanders near Barnard Castle
-Floodplains
-95% land is farmland
-River is very powerful here
-Bed load is much smaller

25

River case study: River Tees

Lower course

-Meanders are much larger and oxbow lakes have formed near Yarm
-Levees have formed when river has flooded
-River not as powerful here
-Very large estuary with mudflats and sandbanks, which support wildlife in the area
-Very industrially developed
-Mouth at North Sea

26

River case study: River Tees

Management

-In upper course, dams and reservoirs control the river’s flow during high and low rainfall
-Better flood warning systems
-More flood zoning
-River dredging reduces flooding

27

Hydrograph

Shows how a river responds to a period of rainfall.

28

River discharge

The volume of water that flows in a river per second.

29

Peak rainfall

The hour of greatest rainfall during a storm.

30

Peak discharge

The time of maximum discharge by the river.

31

Lag time

The period of time between peak rainfall and peak discharge.

32

Falling limb

The period of time when the river’s discharge is falling.

33

Rising limb

The period of rising river discharge following a period of rainfall.

34

Normal flow

The base flow of the river.

35

Physical causes of flooding:

•Prolong and heavy rainfall (saturated soil —> surface runoff)

•Relief (steeper land –> less time to infiltrate –> surface runoff)

•Geology (impermeable rocks –> no infiltration –> surface runoff)

36

Human causes of flooding:

•Urban land use (tarmac impermeable –> no infiltration –> surface runoff)

•Deforestation (less interception —> more surface runoff)

37

List 5 reasons why the effects of flooding worse in LICs than HICs:

-Reliance in primary industry for a living
-Poor infrastructure
-Poor communication
-Poor economy
-Poor housing infrastructure

38

Why are the effects of flooding worse in LICs (such as Bangladesh) than HICs (such as the UK)?

Reliance on primary industry for a living

E.g. farming
Crops destroyed —> no income —> can’t buy food + water —> malnutrition —> poor quality of life —> possible death.

39

Why are the effects of flooding worse in LICs (such as Bangladesh) than HICs (such as the UK)?

Poor infrastructure

Hard for emergency service to access areas at risk / hard to evacuate —> more people suffer —> more likely to die from secondary impacts of flooding like a waterborne disease (e.g. cholera).

40

Why are the effects of flooding worse in LICs (such as Bangladesh) than HICs (such as the UK)?

Poor communication

Lack of warning from media —> less people aware of flood —> less people evacuate in time —> more people drown / suffer from waterborne diseases (e.g. cholera).

41

Why are the effects of flooding worse in LICs (such as Bangladesh) than HICs (such as the UK)?

Poor economy

Country relies on aid —> some of aid could be tied aid —> country becomes dependent on aid —> country could be in debt —> country can’t develop by itself —> increases development gap.

42

Why are the effects of flooding worse in LICs (such as Bangladesh) than HICs (such as the UK)?

Poor housing infrastructure

Homes easily destroyed in flood —> people become homeless —> live in temporary housing which is over crowded + has poor sanitation —> more at risk from disease —> more people die from secondary impacts of flooding.

43

Factors that influence lag time:

Size of drainage basin
Vegetation
Valley side steepness
Soil type
Geology
Amount of rainfall
Urbanisation

The factors that cause RAPID WATER TRANSFER/rapid surface runoff = SHORT lag time.
Factors that cause SLOW WATER TRANSFER/groundwater flow/interception/infiltration = LONG lag time.

44

River management hard engineering method: DAMS AND RESERVOIRS

The dam traps water, which builds up behind it, forming a reservoir. Water can be released in a controlled way.

45

Pros and cons of DAMS AND RESERVOIRS

+ Can be used to produce electricity by passing the water through a turbine within the dam.
+ Reservoirs can attract tourists.

- Very expensive.
- Habitats are flooded often leading to rotting vegetation. This releases methane which is a greenhouse gas.

46

River management hard engineering method: CHANNEL STRAIGHTENING

Cutting through a meander to create a straight channel to speed up the flow of water along the river.

47

Pros and cons of CHANNEL STRAIGHTENING

+ Reduces the risk of flooding in a vulnerable area.
+ Good for shipping.

- Speeding up the river increases flood risk downstream.
- Spoils the natural look of the area.

48

River management hard engineering method: EMBANKMENTS

Raising the banks of a river so that it can hold more water.

49

Pros and cons of EMBANKMENT

+ Cheap with a one-off cost.
+ Allows for flood water to be contained within the river.

- Looks unnatural.
- Water speeds up and can increase flood risk downstream.

50

River management hard engineering method: FLOOD RELIEF CHANNELS

The floodwater flows into the relief channel and is taken either to an area where it can be absorbed, or re-enters the river further down its course.

51

Pros and cons of FLOOD RELIEF CHANNELS

+ Removes excess water from the river channel to reduce flooding.
+ Creates new wetlands which will provide habitats for wildlife.

- Expensive to build.
- If water levels continue to rise, the relief channel may also flood.

52

River management soft engineering method: FLOOD WARNINGS AND PREPARATION

The environmental agency monitors rivers using satellites and computer technology and issues warnings via newspapers, TV, radio and the internet when they are likely to flood so people can prepare.

53

Pros and cons of FLOOD WARNINGS AND PREPARATION

+ People have time to try to protect their properties, e.g. with sandbags.
+ Many possessions can be saved, resulting in fewer insurance claims.

- Some people may not be able to access the warnings.
- Flash floods may happen too quickly for a warning to be effective.

54

River management soft engineering method: FLOODPLAIN ZONING

Allowing only certain land uses on the floodplain reduces the risk of flooding to houses and important buildings.

55

Pros and cons of FLOODPLAIN ZONING

+ More expensive buildings and land uses are further away from the river, so have a reduced flood risk.
+ Less damage is caused, leading to fewer insurance claims.

- Not always possible to change existing land uses.
- Planners have to decide what type of flood to plan for.

56

River management soft engineering method: AFFORESTATION

Trees are planted near to the river. This means greater interception of rainwater and lower river discharge.

57

Pros and cons of AFFORESTATION

+ Relatively cheap.
+ Enhances the environmental quality of the drainage basin.

- Takes a long time for trees to grow.
- People might cut these trees down for their own profit.

58

River management soft engineering method: RIVER RESTORATION

Returning a river to its original course, if it has been artificially changed, by using natural processes and features of a river to slow down the river's flow.

59

Pros and cons of RIVER RESTORATION

+ Reinstating wetlands will provide habitats for wildlife.
+ Reduces flood risk downstream.

- Areas nearest to the river will be vulnerable to flooding again.
- Specific areas will be unable to build on due to floodplains.

60

Flood management scheme case study: Leeds

Location and background

-Leeds is in the north of England in the county of Yorkshire.
-It is located on the floodplain of the River Aire.

61

Flood management scheme case study: Leeds

Why was a scheme required?

-On Boxing Day 2015, Storm Eva caused River Aire to rise by over 2m.
-Environment Agency issued a red weather warning.
-Over 3000 properties were damaged.

62

Flood management scheme case study: Leeds

Management

Environment Agency has introduced a 2 phase plan:

PHASE 1) •moveable weirs •remove island to create capacity •flood walls + embankments (glass walls in city + housing)

PHASE 2) •flood storage areas upstream •widening channel •natural flood management (inc. afforestation)

63

Flood management scheme case study: Leeds

Pros and cons

+ Main routes can remain open during floods.
+ Protected houses + businesses.
+ Thousands of new trees have been planted.

- Scheme will cost around £100mil when completed.
- Removing island has destroyed habitats.