Rivers

Question 1

What is Hydraulic action?

Answer 1

The force of water causing material to be destroyed and carried away.

Question 2

What is abrasion?

Answer 2

Where rocks are thrown against the coastline.

Question 3

What is Solution?

Answer 3

When sea water dissolves certain types of rocks.

Question 4

What is attrition?

Answer 4

When material such as rocks and stones carried by waves hit and knock against each other wearing them down.

Question 5

What is saltation?

Answer 5

A form of transport of sediment on rivers.

Question 6

What is suspension?

Answer 6

A method of transporting very fine sediment in a river.

Question 7

What occurs in the upper course?

Answer 7

Steep gradient, Low discharge, large angular load, waterfalls, interlocking spurs and V-shaped valleys.

Question 8

What occurs in the middle course?

Answer 8

River flattening out, small floodplain, lateral erosion, deposition, getting wider so discharge increases, rocks are getting smaller and rounder, meanders and ox-bow lakes.

Question 9

What occurs in the lower course?

Answer 9

Flat, large floodplain, high discharge, wide channel, small load, estuaries, flood plains and levees.

Question 10

How does a waterfall form?

Answer 10

The river flows over the ledge which has a cap rock on top and soft rock beneath. The river undercuts the soft rock, leaving the cap rock exposed so it falls off. This then deepens the plunge pool and adds fallen rock leading to attrition and abrasion. The waterfall over time retreats backwards, leading to a gorge.

Question 11

How does a V-shaped valley form?

Answer 11

In the upper course the river will erode into their bed, leading to a narrow but deep channel. The rock either side of the channel is weathered due to processes like freeze-thaw, causing material to tumble down from the banks and into the channel where it is removed by the river leading to a V-shaped profile.

Question 12

How does a meander form?

Answer 12

There is a pool or a riffle, causing a change in the direction of the water flow. This change in direction then leads to erosion on one side of the river and deposition on the other due to the slow velocity. This would cause a bend in the river which would change over time due to meander migration. This is due to a helicoidal flow caused by centrifugal forces moving the flow of the water to the river cliff and away from the slip-off slope. Once the meander has evolved enough the neck will be smaller than the widest part called a swans-neck meander. This will in time cut off, leaving an ox-bow lake and eventually an ox-bow lake scar.

Question 13

How does a levee valley form?

Answer 13

The river sits normally first, then after the flood, the water floods onto the floodplain but the velocity is low near the edges of the river. This deposits material onto the edges, building the cliff up. This then repeats, creating Levee’s on each.

Question 14

What is precipitation?

Answer 14

Moisture reaching the ground e.g. rain and snow.

Question 15

What is infiltration?

Answer 15

Water sinking into the soil from the ground surface.

Question 16

What is Interception?

Answer 16

Water being prevented from reaching the surface by trees and grass.

Question 17

What is percolation?

Answer 17

Water seeping deeper below the surface in the rock.

Question 18

What is transpiration?

Answer 18

Water lost through pores in vegetation.

Question 19

What is Groundwater flow?

Answer 19

Water flowing through the rock layer parallel to the surface.

Question 20

What is surface run-off?

Answer 20

Water flowing on top of the ground.

Question 21

What is throughflow?

Answer 21

Water flowing through the soil layer parallel to the surface.

Question 22

What are 2 Physical factors leading to an increased flood risk?

Answer 22

Precipitation with storm rainfall, sudden snow melting and antecedent rainfall over a long period of time. Geology and relief where some rock is impermeable, low lying areas have compacted soil and flooding is less likely in areas of permeable tock such as chalk or limestone.

Question 23

What are 2 human factors that lead to an increased flood risk?

Answer 23

Rural land use where deforestation reduces interception, farming creates channels for water and disappearing fields turning into housing. Urban land-use where new infrastructure is introduced, on greenfield sites so flood plains are taken and disappearing gardens where larger cities are expanded.

Question 24

What is a dam?

Answer 24

They are used for water supply, used to control the flow of the river and used for power.

Question 25

What is channel straightening?

Answer 25

Cutting through meanders to create a straight channel but it increases the velocity of the water, leading to flooding downstream.

Question 26

What are river embankments?

Answer 26

Allowing the channel to hold a greater discharge before flooding, sometimes they are dredged.

Question 27

What are flood relief channels?

Answer 27

They are manmade channels constructed to by-pass an urban area, during times of high flow, the gates are opened to allow water.

Question 28

What is river restoration?

Answer 28

It returns the course of a river that has been artificially changed back to its original course, allowing natural flooding.

Question 29

What is flood-plain zoning?

Answer 29

Restricts different land uses to certain locations on the floodplain. Areas close to the river are used for parkland or playing fields and urban areas are put elsewhere. Reduces losses caused by floods.

Question 30

What is preparing for floods?

Answer 30

Rivers and their basins are monitored using satellites and computer technology. The environment agency issues flood warnings using social media, allowing people to prepare.

Question 31

What is afforestation?

Answer 31

Planting trees increasing interception, increasing transpiration. Takes time but volunteers are used so it is cheap.

Question 32

Why was the Jubilee river scheme needed?

Answer 32

Low-lying land which was prone to flooding contained royal settlements and Eton with high value property.

Question 33

What are the economic issues from the Jubilee river scheme?

Answer 33

It was the most expensive flood relief scheme of £110 million and the weirs were damaged at £680,000

Question 34

What were the environmental issues with the Jubilee river scheme?

Answer 34

In 2014 there was lots of flooding where it joined the Thames which caused flooded fields, the weirs are ugly and also prone to algea.

Question 35

What does the Jubilee river scheme involve?

Answer 35

11.7 KM long, 50 M wide, largest artificial channel. Meanders and reed beds, diverts water from the river and homes.

Question 36

What are the social issues with the Jubilee river scheme?

Answer 36

3000 properties protected but Old Windsor suffers downstream, paddle borders can’t use it as the weirs are dangerous.