Topic 4 UK Rivers

Question 1

What is discharge

Answer 1

The volume of water flowing in a river at one particular point and time

Question 2

What is the course

Answer 2

The path of a river as it flows downhill

Question 3

What are features of the upper course

Answer 3

Steep gradient. V-shaped valley, steep sides, shallow channel

Question 4

What are features of the middle course

Answer 4

Medium gradient. Valley sides wider, deeper channel

Question 5

What are features of lower course

Answer 5

Low gradient. Very wide valley, deep channel.

Question 6

Where does vertical erosion mainly take place

Answer 6

Upper course of the river

Question 7

Where does lateral erosion commonly occur

Answer 7

Dominant in the middle and lower courses of river

Question 8

What is traction (transportation)

Answer 8

Large particles are pushed along the river bed by the foce of water

Question 9

What is suspension (transportation)

Answer 9

Small particles like silt and clay are carried along by the water

Question 10

What is saltation (transportation)

Answer 10

Pebble-sized particles are bouncing along the river bed by the force of the water

Question 11

What is solution (transportation)

Answer 11

Solube materials dissolve in the water and are carried along.

Question 12

What is deposition

Answer 12

When a river drops the eroded material its transporting

Question 13

What does antecedent conditions mean

Answer 13

Pre-existing conditions

Question 14

In what course are waterfalls mostly found in

Answer 14

The upper course

Question 15

How are waterfalls formed

Answer 15

The softer rock is eroded more than the hardrock creating a ‘step’. This gets erodedmore and more until a steep drop is then created. This is called a waterfall. The hardrock is eventually undercut by erosion and collapses. The collapsed rocks are swirled around at the foot of the waterfall and erode the softer rock by abrasion creating a plunge pool. Overtime more undercutting causes the waterfall to retreat leaving a steep-sided gorge

Question 16

How are interlocking sours created

Answer 16

In the upper course of the river most of the erosion is vertically downwards. The creates steep-sided v-shaped valleys. They arent powerful enough to erode laterally so they have to wind around the valleys. The hillsides that interlock with eachother are called interlocking spurs

Question 17

What are meanders

Answer 17

Large bends in rivers commonly found in middle to lower courses of the river

Question 18

Describe the erosion of a meander

Answer 18

The current is faster on the outside of the bend because the river bend is deeper and less friction to slow the water down. Therefore more erosion takes place on the outside of the bend causing river cliffs. The current is slower on the inside of the bend because the river channel is shallower, more friction to slow down water. So eroded material is deposited on the inside of the bend causing slip off slopes

Question 19

How are ox-bow lakes formed

Answer 19

When meanders get larger over time - they can eventually turn into an ox-bow lake. Erosion causes the outside bend ti get closer until there is only a small bit of land left between the bends. The river breaks through this land. And the river flows along the shortest course. Deposition eventually cuts off the meander creating an ox-bow lake.

Question 20

What are flood plains

Answer 20

The wide valley floor on either side of a river which ocassionally gets flooded

Question 21

What are levees

Answer 21

Natural enbankments (raised bits) on the edges of a river channel

Question 22

How are deltas formed

Answer 22

Rivers are forced to slow down when coming across a sea or lake. This causes them to deposit the material that theyre carrying. The sea doesnt wash it away and this builds up intil low lying areas of land is being built up called deltas

Question 23

What climates cause a higher discharge

Answer 23

Wetter climates

Question 24

What does a higher disharge cause

Answer 24

An increased rate of erosion because if w river has a higher volume of water it has more power to erode river banks. Also an increase in transportation as it has more energy to transport material

Question 25

What is lag time in a storm hydrograph

Answer 25

The delay between peak rainfall and peak discharge

Question 26

What is the rising limb in a storm hydrograph

Answer 26

The increase in river discharge as rainwater dlows into the river

Question 27

What is the falling limb in a storm hydrograph

Answer 27

The decrease in river discharge as the river returns to its normal level

Question 28

What is lag time and how does it happen

Answer 28

Lag time happens becausw most rainwater doesnt land directly in the river chanel. There is a delay as rainwater gets to the channel. The rainfall gets to the channel by surface run off, soaking into the ground and flowing underground

Question 29

What happens if more water flows as the runoff in a hydrograph

Answer 29

The lag time will be reduced. Meaning the discharge will increase and the hydrographbwill be steeper because more water gets to the river in a shorter space of time.

Question 30

How does geology and soil type affect the shape of a hydrograph

Answer 30

If there are impermeable rocks, water wont be able to infiltrate (soak into the ground) causing more runoff making the rising limb more steep

Question 31

How does urbanisation affect a storm hydrograph

Answer 31

With an increase in infastructure, there will be more impermeable surfaces usch as concrete so there is more runoff, gutters and drains quickly take runoffs to rivers which rapidly increase discharge

Question 32

How does a flood happen

Answer 32

When the level of a river gets so high it spills over its banks onto the flood plain

Question 33

How does deforestation increase chances of flooding

Answer 33

Removing vegetation and permeable surfaces mean that water that would have been stored in soil or plants and trees now flows quickly downstream

Question 34

Give 4 ways river flooding threatens people

Answer 34

People can be killed or injured by flood water
Roads,bridges and rail lines can be damaged or destroyed
Floodwater is can contaminate with sewage leading to a lack of clean drinking water
People can be made homeless as their houses are damaged or destroyed

Question 35

How can flooding create threats to the environment 4 ways

Answer 35

Flood water contaminated with sewage or rubbish can pollute rivers which can damage wildlife habitats
Farmland can be ruined by sediment being deposited after a flood
River banks are eroded which widens the river channel and increase deposition downstream
The firce if rainwater can uproot trees and plants

Question 36

What are the two types of strategies to deal with flooding

Answer 36

Hard engineering
Soft engineering

Question 37

What is hard engineering

Answer 37

Man made structures built to control the flow of rivers and reduce flooding

Question 38

What is soft engineering

Answer 38

Schemes set up using knowledge of a river and its processes to reduce the side effects of flooding

Question 39

What are 4 examples of hard engineering for river management

Answer 39

Flood walls
Embankments
Flood barriers (flood gates)
Flood barriers (demountable)

Question 40

What are flood walls, are they expensive, effect look of environment?

Answer 40

Artificial barriers built along river banks. Theyre designed to increase the height of the river banks, allowing the river channel to hold more water. They are very expensive and can block the view of the river

Question 41

What are embankments. Are they expensive, do they effect the view of the environment

Answer 41

High banks built along or near the river banks. Prevents water from reaching flood plain. They can be made from earth or other natural materials making them less unsightly than flood walls. Quite expensive to build and severe risk of flooding if water rises above the level of the embankments

Question 42

What are flood gates, are they expensive

Answer 42

Built on river estuaries (where rivers meat the seas) to stop flooding from storm surges or very high tides. They can protect a very large area of ground however wre very expensive and need to be maintained regularly

Question 43

What are demountable flood barriers, what do they do

Answer 43

They provide temporary protection against flooding and only put up when theres a flood forecast. Therefore a risk they wont be put up in time. They are quire expensive to build but dont spoil the look of attractive locations

Question 44

What are two exampkes of soft engeneering strategies

Answer 44

Flood plain retention
River restoration

Question 45

Explain what flood plain retention is

Answer 45

Maintaining the rivers flood plain by not building on it. It helps slow flood wtaers down and maintain the flood plains ability to store water. Costs no money but cant be used in urban areas

Question 46

Explain river restoration, maintanance?negatives?

Answer 46

Involves making the river more natural so the flood plain can flood naturally. Discharge is reduced so less chance of flooding downstream. River is left in natural state so little maintanance required.
However this can cause local flooding especially if nothing is done to prevent majour flooding