Rivers

Question 1

Hydraulic action

Answer 1

Force of the water breaks rock away from the river channel

Question 2

Abrasion

Answer 2

Eroded rocks scrape at and break away the river channel

Question 3

Attrition

Answer 3

Erode rocks collide and break up/ rub together and smooth edges

Question 4

Solution ( erosion)

Answer 4

Some rocks will dissolve, eg chalk

Question 5

Traction

Answer 5

Large particles pushed along a river bed

Question 6

Saltation

Answer 6

Pebble sized particles are bounced along a river bed.

Question 7

Suspension

Answer 7

Small particles are carried in the river.

Question 8

Solution ( transportation)

Answer 8

Materials dissolved in the water are carried along in the river

Question 9

Deposition

Answer 9

When a river drops transported material. This occurs when rivers lose velocity/ energy.

Question 10

Why do rivers lose energy

Answer 10

The water is shallower
The river reaches its mouth, and is pushed back by the tide
The volume of water falls
The amount of erode material increases.

Question 11

Upper course of a river

Answer 11

V shaped valley, steep sides, narrow and shallow channel

Question 12

Middle course of a river

Answer 12

Gently sloping valley, wider and deeper channel

Question 13

Lower course of a river

Answer 13

Very wide, almost completely flat, very wide and deep channel

Question 14

How are waterfalls formed?

Answer 14

The waterfalls are formed in the upper course of a river.
1- the river flows over an area of hard and soft rock
2- soft rock is eroded and a step forms
3- a steep drop is created, resulting in a waterfall.
4 - hard rock is undercut and eventually collapses.
5- collapsed rock erodes soft rock, so a plunge pool is created
6- the waterfall will continue to retreat and a deep gorge will remain.

Question 15

How are interlocking spurs formed?

Answer 15

Vertical erosion in the upper course creates steep sided, V shaped valleys. River lacks power to erode laterally so winds around hillsides.

Question 16

How are meanders formed?

Answer 16

Meanders are formed due to there being a deeper outside bend in the river which will have a faster current and therefor more erosion, creating a river cliff.
Whereas the shallower bend has a slower current, so more deposition will take place, resulting in a slip off slope.
Meanders form in the middle course.

Question 17

How are oxbow lakes formed?

Answer 17

The outside bends of meanders get closer, until only separated by a small bit of land. The river will eventually break through this small bit of land, often due to floods, and the river will flow along the new shorter course. Deposition cuts off the meander, forming an oxbow lake.
Oxbow lakes are also formed in the middle course of a river.

Question 18

How are flood plains formed?

Answer 18

Flood plains are a wide, flat valley floor on either side of a river.
The river will flood, and the water slows down and loses energy. This means that material is deposited and a flood plain builds up.

Question 19

How are levees formed?

Answer 19

When a river floods water deposits material on the flood plains. This material will build up after an increased amount of flooding, and levees are created. The heaviest material is also deposited closest to the channel, and the logger sediment that can be carried further is despised further away from the river channel.

Question 20

How are estuaries formed?

Answer 20

Due to the river channel meeting the tide, the river loses a lot of energy. Therefor silt and sand is deposited, and this build up creates mudflats.

Question 21

How does relief of the land effect flood risk?

Answer 21

Steeper valley sides means that water flows into the river channel faster, and therefor discharge increases rapidly.

Question 22

How does the geology increase flood risk?

Answer 22

Some rocks and clay soils are impermeable, which will increase surface runoff.

Question 23

How does heavy rainfall increase flood risk?

Answer 23

Water arrives to quickly to infiltrate the soil, meaning that surface runoff increases into the river. Prolonged rainfall saturates the soil so further rainfall can’t infiltrate it, increasing surface runoff.

Question 24

How does deforestation affect flood risk?

Answer 24

Trees intercept and store rainwater. Cutting them down increases the amount of water entering the river channels.

Question 25

How does human land use affect the flood risk?

Answer 25

Impermeable building materials or surfaces increase surface runoff. Drains also rapidly transport runoff to rivers, increasing discharge.

Question 26

Hard engineering.

Answer 26

Artificial structures that are built to control rivers and reduce flooding.

Question 27

Dams and reservoirs

Answer 27

Dams and reservoirs are designed to control water flow and prevent flooding. Dams also supply potential for hydroelectric power, and these two structures can be popular tourist sights. However dams and reservoirs are very expensive, and construction of dams can flood settlements behind it.

Question 28

Channel straightening

Answer 28

Is the straightening of the river channel so the water flows quicker and reduces flood risk, also means less build up of deposited material. However this can increase flood risk further upstream, and fats moving water can cause erosion.

Question 29

Embankments

Answer 29

Embankments are artificial walls built along the sides of a river. These greatly increase the rivers total capacity and are very effective. However they are expensive and unnatural looking, and whilst effective they can break, causing further economic problems for the area.

Question 30

Soft engineering

Answer 30

Schemes set up using knowledge of the river and its processes. These processes aim to work alongside the environment.

Question 31

Flood warnings and preparation.

Answer 31

This is designed to warn people in advance of an incoming flood. This gives people time to move their valuable possessions and prepare for floods/ evacuate. However this strategy does nothing to prevent floods, and may give people a false sense of security.

Question 32

Flood plain zoning.

Answer 32

Means that urban areas are built further away from the river, and that low value land, eg grazing fields, are built closer to the river. This means that high value land is not lost, reducing the damage the flood may cause. However this strategy is not 100% effective, as urban expansion is limited, and also this can nit help existing settlements who have already set up closer to a river.

Question 33

Afforestation

Answer 33

Aims to plant trees so that more water is intercepted, and less water can reach the river. However this does mean that less farmland is available.

Question 34

River discharge

Answer 34

Volume of water flowing per second, measured in cubic metres per second/ cumecs.

Question 35

What is a hydrograph?

Answer 35

A graph that shows how discharge at a certain point in a river changes over time in relation to rainfall.

Question 36

The river tees flood management

Answer 36

Since 2002 11million pounds has been invested to protect The river tees and local residents from harm.

Question 37

Flood gates in the river tees?

Answer 37

Set in High concrete barriers. These can be raked to separate the residents of Yarm from the floodwater.

Question 38

Embankments along the river tees.

Answer 38

These embankments are also located in Yarm to protect the town from flooding by increasing the river capacity.

Question 39

What is the tees barrage?

Answer 39

Constructed in 1985 and costing 54 million pounds, the tees barrage acts as a barrier between the tide and the river. It is now kept at a permanently high level to reduce the risk of flooding at a high tide or in a storm surge.

Question 40

What is the cow green reservoir?

Answer 40

Constructed in the 1970s to provide water to local industries and to help with flood control, the reservoir is 1/4 of a mile long and holds back 40 million tonnes of water.