River Landscapes and Processes

Question 1

What are the four ways in which rivers transport materials?

Answer 1

Traction, Saltation, Suspension and Solution.

Question 2

What is Traction?

Answer 2

Large sediment roll along the river bed.

Question 3

What is saltation?

Answer 3

Where small pieces of shingle or large grains of sand are bounced along the river bed.

Question 4

What is suspension?

Answer 4

Where small particles like sand or clay are carried by the water stream. This can make water look cloudy.

Question 5

What is solution?

Answer 5

Where minerals are dissolved in river water and carried downstream.

Question 6

What is the stream like in the upper course?

Answer 6

Since the gradient is greater it has more power to erode downwardly, forming a V-shaped valley.

Question 7

What is a stream like in the mid course?

Answer 7

As gradient had decreased, the river begins to erode laterally and widening, forming meanders and ox-bow lakes.

Question 8

What is a stream like in the lower course?

Answer 8

The gradient is very shallow and thus the stream is increasingly wide, forming floodplains and levees.

Question 9

What is a river mouth?

Answer 9

Where a river ends, either when it joins another river or the sea.

Question 10

What is a long profile?

Answer 10

A slice through the river from source to mouth showing elevation changes throughout its course.

Question 11

What is the river source?

Answer 11

The start of the river, normally found at high elevation in areas glaciated or of high rainfall.

Question 12

What is river channel shape?

Answer 12

The width and depth of the river.

Question 13

What is the river discharge?

Answer 13

The amount of water passing a specific point at a given time, measured in cubic metres per second.

Question 14

What is river volume?

Answer 14

The amount of water in a river.

Question 15

What is river velocity?

Answer 15

The speed of the river.

Question 16

What is a valley profile?

Answer 16

A slice across the river showing changes in height across the valley.

Question 17

What is a river confluence?

Answer 17

The place where two rivers meet.

Question 18

How does a levee form?

Answer 18

A levee is a raised bank formed on the banks of a river when sediment is deposited on the sides during repeated flooding.

Question 19

What is a floodplain?

Answer 19

A low-lying area of land that frequently floods due to its close proximity to a river.

Question 20

What are interlocking spurs and how do rivers move through them.

Answer 20

Interlocking spurs are outcroppings in a valley which form in areas of high altitude in the upper course. In this region, the river is shallow and there is a lot of friction, thus erosion occurs a lot. Due to the steep gradient a V-shaped valley forms and the rover path winds through the interlocking spurs.

Question 21

How do waterfalls form?

Answer 21

They form due to erosion and the local geology. Less resistant, softer rock is eroded faster, leaving an overhang of more resistant, harder rock. In time this heavy rock becomes too heavy and falls.

Question 22

How do meanders form?

Answer 22

The point of fastest flow erodes on one side, and material is deposited on the other side, so the highest erosive power moves to the other side diagonally, so the material is now deposited on the other side.

Question 23

How does an oxbow lake form?

Answer 23

At certain points in meanders there id a faster route that the river can take, instead of winding around the usual path, so during times of flooding more water from the stream cuts through this path. Over time the old route has sediment deposited on it, cutting it off from the old stream, forming a lake cut off from the river called an oxbow lake.

Question 24

What is interception?

Answer 24

When trees stop precipitation hitting the ground.

Question 25

What is throughflow?

Answer 25

When water travels through soil towards a river.

Question 26

What are the physical causes of flooding?

Answer 26

-Heavy rainfall - if there are large amounts of rainfall the water will saturate the ground so water will more easily flood.
-Cloudburst in a thunderstorm - the rain droplets are so large and fall so quickly that there is no time for water to sink into the ground; water runs very quickly into the river and causes flooding.
-Sudden rise in temperature - a rapid thaw can happen; rivers are unable to cope with the amount of water and flood.
-Silted up river channels - this makes the channel smaller and more likely to flood.

Question 27

What are the human causes of flooding?

Answer 27

-Removal of vegetation on valley slopes - If there is less interception water will move to the river faster.
-Settlements built on the floodplains - storm drains allow water to move into rivers at a greater speed.
-Global warming - melting of polar ice caps and a rise in sea level leads to more flooding.
-Dams bursting - this causes excess water in the channels and flooding of large areas.

Question 28

What are the impacts of flooding?

Answer 28

-Damage to people’s homes and belongings.
-Loss of life from drowning of people and livestock.
-Contamination of fresh water by sewage water.
-Communication and transport links destroyed.
-Disruption to gas and electricity supplies.
-Fields of crops can be destroyed so a lackof food.

Question 29

What are the advantages of dams?

Answer 29

-Effective for many years
-Very visible - makes residents feel safe
-Stores water behind the dam - hydroelectric power can be produced using this.

Question 30

What are the disadvantages of dams?

Answer 30

-They can be ugly - putting tourists off
-They are very expensive to build
-They can create problems for fish trying to swim upstream

Question 31

What are the advantages of reservoirs?

Answer 31

-They can provide drinking water
-Can be used for recreation e.g. sailing

Question 32

What are the disadvantages of reservoirs?

Answer 32

-Very expensive to create and maintain them
-Settlements and farmland can be lost during flooding
-Natural processses are disrupted
-There is a visual impact on the environment

Question 33

What are the advantages of channelisation?

Answer 33

-They last long
-Visual, so residents feel safe
-The river channel can hold more water, so less likely to flood

Question 34

What are the disadvantages of channelisation?

Answer 34

-Expensive
-Possible flooding in other, less prepared areas
-River landscape is changed and perhaps unnatural

Question 35

What are the advantages of floodplain zoning?

Answer 35

-Saves money
-Provides habitats for wildlife
-Provides recreational areas like sports fields

Question 36

What are the disadvantages of floodplain zoning?

Answer 36

-Flooding makes recreational land unusable for weeks
-Large areas are unable to be built on
-The environment is changed every time it floods

Question 37

What is a levee?

Answer 37

A depositional landform formed on the river bank when the river floods or during high rainfall.

Question 38

What is a floodplain?

Answer 38

An area that is regularly flooded.

Question 39

What is the channel shape of a river?

Answer 39

The width and depth of the river.

Question 40

What is the discharge of the river?

Answer 40

The amount of water passing a specific point at a given time, measured in metres per second.

Question 41

What is the velocity of the river?

Answer 41

The speed and direction, measured in metres per second.

Question 42

What is a river confluence?

Answer 42

The place where two rivers meet.