Component 2 - Rivers

Question 1

Describe the water cycle

Answer 1

1. Water evaporates and condenses into clouds,
2. This falls onto the land, where some of it re enters the atmosphere through evapotranspiration, some will go into rivers. The rest soaks through the soil through infiltration and will return to the sea.
3. Some undergoes percolation and turns into groundwater, this will take 1000s of years to return to the sea.

Question 2

What are the 3 courses of a river?

Answer 2

Upper, middle and lower.

Question 3

Where is the upper course of a river found?

Answer 3

The upper course is found high up in mountains.

Question 4

What are the features of the upper course?

Answer 4

1. The river doesn’t flow fast and is small.
2. River rolls stones across the river bed through traction
3. The river gathers minerals from mountain rocks
4. River flows in interlocking spurs
5. Forms V-shaped valleys
6. Waterfalls

Question 5

What are the features of the middle course?

Answer 5

1. Meanders
2. River flows faster
3. Carries soils and clays, as well as minerals from upper course.
4. Cities found here
5. Murky

Question 6

Where is the middle course of a river found?

Answer 6

The middle course is found on wider, flatter and open plains.

Question 7

Where is the lower course of a river found?

Answer 7

The lower course is found near the coast.

Question 8

What are features of the lower course?

Answer 8

1. Extremely wide and flat
2. River is slow at high tide, fast at low tide
3. Supports large shipping lanes
4. Sediment and minerals deposited making soil very fertile
5. Industry, farms and ports found here.

Question 9

What are the 4 types of erosion found mostly in the upper course?

Answer 9

Abrasion, Attrition, Hydraulic action and solution

Question 10

How do V shaped Valleys form?

Answer 10

1.The river cuts downward into the land, as stones are dragged along the river bed.
2.The sides of the valley are exposed and are eroded by weathering.
3.The weathered material falles via gravity, into the river where it is carried away. Creating a V shaped valley

Question 11

How are waterfalls formed?

Answer 11

1.Begins on a downhill slope when a layer of soft rock sits beneath a layer of harder rock.
2.Overtime the soft rock erodes faster, creating a step in the river
3.The soft rock is eroded further, until a steep drop is created - a waterfall

Question 12

How are gorges formed?

Answer 12

1. The waterfall undercuts the hard rock, which creates an unsupported overhang
2. The hard rock collapses and the waterfall recedes.
3. The collapsed rocks swirl around at the foot of the waterfall, where they use abrasion to create a plunge pool.
4. This creates a gorge, which gets bigger as the waterfall recedes.

Question 13

How are Oxbow lakes formed?

Answer 13

1. The river meanders so far it connects back up with itself.
2. The river takes shortest path, and sediment is deposited blocking off the old meander
3. Forming an oxbow lake.

Question 14

What are the main types of flooding?

Answer 14

1. Glacial outbursts
2. Fluvial flooding
   3.coastal flooding
   4.Saturation flood
   5.Sewer flood
3. Flash flood
   7.Catastrophic floods
   8.Liquefation floods.

Question 15

How do glacial outbursts happen.

Answer 15

1.Volcano erupts, or there is increased activity beneath a glacier.
2. Melting of huge volumes of ice causes torrent of water.

Question 16

How does Fluvial flooding happen?

Answer 16

1. When a river bursts its banks due to the inflow being greater than the outflow.
2. Caused by heavy rain

Question 17

What is the most common type of flooding in the UK?

Answer 17

Fluvial flooding

Question 18

What is fluvial flooding good for?

Answer 18

Creating fertile land

Question 19

What is coastal flooding caused by?

Answer 19

1.Sea storms and rising sea levels cause low lying land to flood
2. Worsened by climate change

Question 20

How do Saturation floods work?

Answer 20

1. Days of moderate rainfall cause the soil to become saturated, so it floods

Question 21

How does sewer flooding work?

Answer 21

1.Sewer drainage becomes overwhelmed

Question 22

What is dangerous about sewer flooding?

Answer 22

It is a significant biohazard, contamination can take weeks to clean

Question 23

Why is sewer flooding common in the UK

Answer 23

Sewers are old.

Question 24

Why are flash floods dangerous

Answer 24

It happens suddenly and violently, it is more common in cities because there is nowhere for water to go.
Hard to predict

Question 25

How does liquefaction flooding work?

Answer 25

After an earthquake, groundwater is pushed out of the ground by the vibrations. It is near instantaneous, however is rarely deep. Makes rescue harder though.

Question 26

What is traction?

Answer 26

Material rolled along the riverbed during high flow

Question 27

What is suspension?

Answer 27

Material floating in the water, making it murky

Question 28

What is saltation?

Answer 28

Material bouncing along the riverbed

Question 29

What is solution?

Answer 29

Dissolved material such as salts, invisibly carried in flow

Question 30

How do you work out the base flow of a river?

Answer 30

Depth X width X velocity = base flow

Question 31

What does base flow mean?

Answer 31

Normal rate of discharge of a river.

Question 32

What is a hydrograph?

Answer 32

A type of graph used to show how the flow of a river changes over time.

Question 33

What does cumecs stand for?

Answer 33

Cubic Metres Carried per Second

Question 34

What are hydro dams?

Answer 34

Huge concrete structures that block rivers and produce electricity

Question 35

What are raiseable barriers?

Answer 35

Huge structures that can be opened or closed to prevent water surging up or down a river.

Question 36

What are wiers?

Answer 36

Small walls that slow a river down.

Question 37

What is hard engineering?

Answer 37

The use of large structures to control natural processes

Question 38

What is soft engineering?

Answer 38

The use of ecology and the natural environment to control natural processes.

Question 39

What is vertical erosion, and where is it most common?

Answer 39

1.It deepens the river valley and channel, making it v shaped 2.It is dominant in the upper course

Question 40

What are some reasons why a river would deposit material?

Answer 40

1.The volume of water in the river falls 2.The amount of eroded material in the water increases 3.The water is shallower 4.The river reaches its mouth

Question 41

Why do rivers form interlocking spurs in the upper course?

Answer 41

1.The rivers aren't powerful enough to erode laterally, so they wind around the hill side, creating interlocking spurs.

Question 42

How are meanders formed?

Answer 42

1.The current is faster on the outside of the bend, because the river channel is deeper so there's less friction 2.So more erosion occurs there, forming river cliffs, and bending the river outwards 3.The current is slower on the inside of the bend, as the river channel is shallower so there is more friction 4.This means eroded material is deposited here, forming slip off slopes and causing the river to bend further

Question 43

What are levees and how are they formed?

Answer 43

1.natural embankments along the edges of a river channel 2.During a flood, material is deposited across the whole flood plain 3.The heiest material is deposited closest to the river channel, because it gets dropped first when the river slows down. 4.Overtime this builds up, creating levees.

Question 44

how are deltas formed?

Answer 44

1.The rivers slow down when they meet the sea 2.This causes them to deposit material 3.This builds up and blocks the channel, forceing the river to split up into distributaries 4.This then becomes a delta.

Question 45

What is peak discharge?

Answer 45

The highest discharge in the period of time you're looking at

Question 46

What is the rising/falling limb?

Answer 46

1.The increase/decrease in river discharge as rainwater flows into, or out the river.

Question 47

What is the lag time?

Answer 47

The delay between peak rainfall and peak discharge

Question 48

What physical factors affect hydrographs?

Answer 48

1.geology/soil type - water can't infiltrate impermable rocks or soil, so the river fills faster 2.Slope - the steeper, the quicker the river fills 3.Previous weather conditions - if it was wet, the water will be saturated, making the river fill quicker

Question 49

How can human factors affect hydrographs?

Answer 49

1.Water can't infiltrate into impermeable surfaces like roads, so there's more runoff 2.Drains quickly take water to rivers 3.Deforesting trees reduces the amount of water taken up by them, increasing runoff too

Question 50

What are some soft engineering ways to manage flooding?

Answer 50

1.Flood plain retention 2.River restoration

Question 51

What is flood plain retention?

Answer 51

1.Not building on the rivers flood plain, so that the river has somewhere to flood

Question 52

What is river restoration?

Answer 52

1.Making the river more natural, so the flood plain can flood naturally 2.This means there is less risk of flooding downstream, as the discharge is reduced.