Rivers

Question 1

What is evaporation?

Answer 1

Water is heated by the sun - becomes water vapour and rises

Question 2

What is transpiration?

Answer 2

Evaporation from trees and plants

Question 3

What is condensation?

Answer 3

Water vapour cools as it rises and forms clouds

Question 4

What is precipitation?

Answer 4

Clouds release water as rain, hail and snow

Question 5

What is interception?

Answer 5

Precipitation lands on plants, trees or buildings - either runs off or evaporates

Question 6

What is surface storage?

Answer 6

Water lies on uneven ground - as puddles or lakes

Question 7

What is surface run-off?

Answer 7

Water travels as overland flow towards the river - occurs when soil is saturated

Question 8

What is infiltration?

Answer 8

Surface water soaks into soil

Question 9

What is soil storage?

Answer 9

Water is held in open spaces in the soil

Question 10

What is throughflow?

Answer 10

Water flows through the soil, under the influence of gravity, towards a river - slow flow

Question 11

What is percolation?

Answer 11

Water moves downwards through the soil into permeable rocks

Question 12

What is groundwater?

Answer 12

Water is held in porous rocks - saturated zone is known as the water table

Question 13

What is groundwater flow?

Answer 13

Very slow flow occurs in rocks and feeds rivers and springs

Question 14

What is the source of a river?

Answer 14

The area in which a river begins

Question 15

What is the mouth of a river?

Answer 15

Where a river ends it’s journey, flowing into the sea or a lake

Question 16

What is a tributary?

Answer 16

A smaller river that joins a larger river

Question 17

What is the confluence?

Answer 17

The point at which two rivers join

Question 18

What is the watershed?

Answer 18

The boundary between two drainage basins marked by a ridge of high land

Question 19

What is the drainage basin?

Answer 19

The area which is drained by a river and it’s tributaries

Question 20

What is the drainage density?

Answer 20

The total length of all the streams in the basin divided by the total area of the basin

Question 21

How is an oxbow lake formed?

Answer 21

In a meander the water is pushed to the outside bend. Greater velocity means that the river has more energy to erode. Processes such as abrasion will cause lateral erosion. This happens when material carried by the river is hurled at the bank which causes a sandpapering action. Continual erosion on the outside bend narrows the meander neck. The river floods and takes a shortest route, cutting through the neck. The fastest current is now in the centre of the channel, however water continues to slowly flow around the meander. Deposition occurs along the banks of the river. The meander becomes cut off to leave an oxbow lake. The lake will slowly dry up unless rainfall is very high.

Question 22

What are meanders?

Answer 22

Meanders are bends in rivers. There is erosion and deep water on the outside of the bends. There is deposition and shallow water on the inside of the bends.

Question 23

What is traction?

Answer 23

Boulders and pebbles are rolled along the river bed at times of high discharge

Question 24

What is saltation?

Answer 24

Sand sized particles are balanced along the river bed by the flow of water

Question 25

What is solution?

Answer 25

Some minerals dissolve in water such as calcium carbonate. This requires very little energy.

Question 26

What is suspension?

Answer 26

Fine clay and sand particles are carried along within the water even at low discharges

Question 27

What is deposition?

Answer 27

This is when a river drops off material

Question 28

Explain the formation of a waterfall and gorge

Answer 28

Waterfalls often form in the upper stages of a river where it flows over different types of rock. The soft rock erodes more quickly due to abrasion, undercutting the hard rock. The hard rock is left overhanging and because it isn’t supported it eventually collapses. The fallen rocks crash into the plunge pool this is created by hydraulic action. They swirl around, causing more erosion. Overtime this process is repeated and the waterfall moves upstream. A steep sided gorge is formed as the waterfall retreats.

Question 29

What is a delta?

Answer 29

A delta is formed at the mouth of a river, it is a flat area of land crossed by many streams and channels called distributaries

Question 30

What are the main features needed for the formation of a delta?

Answer 30

The sediment load in the river on substantial, due to active erosion in the upside coarse
Needs to be a sheltered sea or lake where there are no strong tides or currents
The supply of sediment is greater than the rate at which tides or currents are able to remove it from the mouth of the river

Question 31

Where is the Ganges delta located?

Answer 31

On the northern end of the Bay of Bengal, Bangladesh

Question 32

How does a delta form?

Answer 32

When a river reaches a lake or the sea the water slows down and loses the power to carry sediment. The sediment is dropped at the mouth of the river. Some rivers drop so much sediment that waves and tides can’t carry it all away. It builds up in layers forming a delta.

Question 33

What were the causes and effects of flooding in the river Rhine?

Answer 33

Dykes - these are tall walls that are built around rivers to allow for a rise in river water preventing flooding
Polders - these are areas of reclaimed land that are pumped free of water and used for farming

Question 34

What are the benefits and problems of flood retention basins?

Answer 34

They reduce the amount of water in the main river
They are costly
Crops are lost as they take up farm land

Question 35

What are flood retention basins?

Answer 35

They reduce the amount of water in the main river. When water becomes dangerously high some water is diverted into the basin for about 12 hours until the basin is full and the crisis is over.

Question 36

What are dykes and what are they made of?

Answer 36

Tall walls that are built around rivers to allow a rise in river water preventing flooding
Made of sand, stones, soil, strengthened with steel

Question 37

How many countries have tributary rivers that feed into the river Rhine?

Answer 37

9

Question 38

Name the 3 cities affected by the floods

Answer 38

Cologne (Germany)
Ophemert (holland)
Well (holland)

Question 39

What were the natural causes of the flood?

Answer 39

Warm wet weather melting snow and glaciers
Increase surface run off due to melted snow
3x average rainfall in Switzerland making the soil saturated

Question 40

How did people’s activities contribute to the flood?

Answer 40

Buildings increased the spread of impermeable man-made surfaces and embankments have been built closing off former flood plains. This creates a faster and deeper river flow.

Question 41

Why did the Netherlands suffer the worst effects of the Rhine floods?

Answer 41

75% of the land is below sea level. 250,000 had to be evacuated as there were signs that the dykes were crumbling.

Question 42

Describe and explain the steps which are being taken to reduces flooding along the river Rhine

Answer 42

Reservoirs can be built in the upper courses of rivers to store water preventing sudden flooding
Rivers can be deepened and widened
The building of embankments, flood relief channels, barrages, flood plane zoning and improving channel efficiency

Question 43

Describe the causes and effects of the river Rhine flooding (7mark)

Answer 43

Heavy rainfall meant that soils were saturated. This combined with unusually mild temperatures that melted snow in the alps, produced far too much water with which the basin could cope. Groundwater stores were also high as winter rain in the Rhine basin had increased by 40% since 1900. Human actions made the problem of flooding much worse. Three times more land in Germany is built up than in 1900. This means the spread of impermeable man-made surfaces has increased the speed with which run-off enters the river channels. Farming techniques are more intensive, compacting soils and leading to more open land. Soils therefore store less water and surface run-off. The damage by acid rain in the Black Forest, trees cleared for development and farmers cutting out hedges mean less vegetation to soak up water. To reduce journey time for barges the Rhine has been straightened and is now 50km shorter. Deepening and canalising has also taken place. Together they speed up flow so that a flood surge takes 2-3 days, as opposed to 5, to move downstream. In early February 1995, the Rhine suffered catastrophic flooding. Disruption was greatest on the Netherlands where 75% of the land is below sea level, 250,000 people had to be evacuated as there were signs the dykes were crumbling. The floods caused 27 deaths, disrupted drinking water and power supplies, telephones and roads. Farmers were forced to move their cattle which gave them diseases and left them producing less milk for a while, due to the shock of transportation, which therefore caused the farmers to lose money.