Geography- river landscape and processes

Question 1

What is Hydraulic Action:

Answer 1

The force of the river against the bed and the banks can cause air to be trapped in cracks and crevices. The pressure weakens the banks and gradually wears it away. This is most effective when the water is moving fast and there is a lot of it!

Question 2

What is Abrasion:

Answer 2

The river load rubs against the bed and the banks of the river. This action causes some of the material to break off, by a sand papering action called abrasion, and causes the bank to collapse.

Question 3

What is Attrition:

Answer 3

Rocks being carried by the river smash together and break into smaller, smoother and rounder particles.

Question 4

What is Solution:

Answer 4

Soluble particles are dissolved into the river.

Question 5

A river erodes in 2 directions – downwards or sideways. This is known as:

Answer 5

Vertical and lateral erosion

Question 6

Where does transportation, erosion, deposition happen most in a river.

Answer 6

Source/Mouth

Question 7

Two different strategies of management

Answer 7

hard and soft engingeering

Question 8

What is hard engineering

Answer 8

man made/built structures to protect areas from flooding. Normally big, expensive projects

Question 9

What is soft engineering

Answer 9

Using natural processes and adapting to flood risks

Question 10

Pros and cons of hard engineering.

Answer 10

Expensive / Costly / Environment

Question 11

Pros and cons of soft engineering.

Answer 11

Inexpensive / Sustainable

Question 12

How is an oxbow lake formed? (AO3)

Answer 12

1. The outside of the meanders have the quickest water (thalweg) and are eroded by hydraulic action and abrasion.
2. The outside of the meanders move closer together narrowing the ‘neck’ in between.
3. Eventually (usually during a flood) the river cuts straight across the neck following the quickest route
4. After this the river slows down by the old bend and deposits material cutting off a oxbow lake

Question 13

What is a floodplain

Answer 13

A flat area surrounding the river for water to spill on to.

The river erodes laterally (sideways) not vertically.

The river valley is widened creating a large flat area.

When the river overflows (floods) material is deposited as the water loses energy.

Over time the sediment builds up in layers creating a floodplain.

Question 14

What Is a Hydrograph

Answer 14

A hydrograph is a graph showing the rate of flow versus time past a specific point in a river, channel, or conduit carrying flow.

Question 15

What does a Hydrograph tell you

Answer 15

Steeper hydrographs mean more likely to be a storm event or urban area. The lag time is shorter in these storm hydrographs.

Question 16

Human Factors Affecting Storm Hydrographs

Answer 16

• Drainage systems that have been created by humans lead to a short lag time and high peak discharge as water cannot evaporate or infiltrate into the soil.
• Area that have been urbanised result in an in crease in the use of impermeable building materials. This means infiltration levels decrease and surface runnoff increases. This leads to a short lag time and an increase in peak discharge.

Question 17

State one type of chemical weathering that might have an impact on river landscape.

Answer 17

Carbonation/acid rain (1)

Dissolution/solution weathering (1)

Question 18

Channelisation is an example of hard engineering.

Explain one way channelisation helps manage river landscapes.

Answer 18

Making the channel wider or deeper (1) increasing the capacity of the river to hold water (1)

Question 19

what is channelisation

Answer 19

is a diliberate attempt to alter the natural geometry of the river.

Question 20

outline one physical cause of flooding.

Answer 20

The physical causes of flooding are:

1. Prolonged precipitation which saturates the soil until the water table (the level of saturated ground in the soil) reaches the ground surface.
2. Intensive precipitation over a short period of time. This is more likely to lead to after a long period of drought when the soil will be baked hard and it is more difficult for the rainfall to infiltrate the soil.
3. Rapid snow melt when the ground below is still frozen makes it difficult for the excess moisture to infiltrate the soil.

Question 21

outline one human cause of flooding

Answer 21

1. Urbanisation means more surfaces of concrete and tarmac which are impermeable. Precipitation cannot infiltrate these surfaces and is channelled into drainage networks and gets to the river very quickly, making it more likely to flood. Also as urban populations increase houses are built on more marginal land including flood plains.
2. Deforestation can cause flooding as trees are excellent at intercepting rainfall and storing water and when they are removed the precipitation will reach the river channel more quickly.
3. The building of levees (an embankment built to prevent a river overflowing) and dams can reduce flooding but if these protection measures fail they can cause catastrophic flooding.