Theme A- Part 2- River Processes And Features

Question 1

What is discharge

Answer 1

The amount of water flowing in a river at any point in a certain time

Question 2

What is load

Answer 2

The amount of material a river is carrying ranging from small sediment to large boulders

Question 3

What changes occur to the river as we go downstream

Why

Answer 3

Gets wider and deeper because of more lateral and vertical erosion taking place
Increasing discharge because of adding tributaries
Increasing velocity= less friction to overcome as upper couse has angular rocks and shallow channel

Question 4

Why is the upper course angular and the lower course rounded

Answer 4

Weathering of bare rock happens in upper course because it is more exposed, the rock falls down the steep valley sides into the river. It will still be very angular

As the rocks go down the river the rocks hit the side of the river bed and other rocks which are apart of the load.

This knocks off any sharp edges making the rock smooth and rounded by the time it reaches the lower course

Question 5

What is vertical (downwards) erosion

Answer 5

When the load of a river consists of coarse products that scrap and rub against the channel of the river, creating steep sides

Question 6

The happens in lateral erosion?

Answer 6

Points of a river channel where the river is flowing especially fast, the water itself has so much energy it can wash away the banks which cause the bank to be undercut and collapse
Side wards erosion

Question 7

What is abrasion

Answer 7

The grinding of rock fragments ,carried by the river, along the river bed and banks which deepen and widen the channel

Question 8

What is the process of solution

Answer 8

When the river water reacts with the soluble minerals in the rocks which dissolves them

Question 9

What is attrition

Answer 9

The collision of rock fragments, which break down rocks and makes them smoother

Question 10

What is hydraulic action

Answer 10

The mechanical weathering based on the shear force of water, eg. Undermining river banks on the outside of the meander and forcing air into exposed rocks in waterfalls

Question 11

What is traction

Answer 11

The rolling of large rocks along the river bed
Requires a lot of energy
The bed’s biggest load is only moved in times of floods

Question 12

What is saltation

Answer 12

The bouncing along of a medium sized load along the river bed

Question 13

What is suspension

Answer 13

The smallest load of the river eg. Clay and sand

Held up by the water making it look opaque

Question 14

What is the transportation process of solution

Answer 14

When soluble minerals are dissolved in water and carried by river
This can change the colour of the river

Question 15

What is deposition
How does it occur
When is it likely to occur

Answer 15

When the velocity (speed and direction) of the river decreases therefore the energy also decreases, this mean the river cannot hold the load anymore dropping of the load starting with the biggest first
When a river meets the sea as the flow decreases
Where the river gets shallow
When there has been a sudden increase of load eg. a landslide
When a rivers floods on to a flood plain, where it flows slowly

Question 16

How does a water fall form

Answer 16

Usually in the upper course, where it is mountainous
When there is a layer of hard rock with softer rock underneath it
The river erodes the softer rock so a step is formed
Due to hydraulic action and erosion the step is deepened and a waterfall is formed
Eventually erosion undercuts the hard rock making it unstable and it falls
The waterfall retreats backwards leaving a gorge

Question 17

What is a meander

Answer 17

Formed when the gradients (slope) of a river levels out

Has continuously changing features of the result of a changing velocity (speed and direction) across the river channel

Question 18

What changes occur on the outside of the river

Answer 18

The water flows very fast (high velocity) so vertical erosion takes place, this undercuts the side bed creating a river cliff and deepening the channel

Question 19

What happens in the inside bend of a meander

Answer 19

Velocity (speed and direction) is lowest here so little energy so little erosion
Cannot hold load any more, so the river deposits creating a slip-off slope

Question 20

What part of a course of a river is a meander being formed and réforme d

Answer 20

The middle and lower course

Question 21

How is an ox-bow lake formed

Answer 21

When a two meanders get bigger and bigger and their necks become closer and closer, until they join and the meander has been cut of

Question 22

How are flood plains formed

Answer 22

When a meander goes back and fourth it creates flat land on each side of its channel
Due to floods dropping its load sediment is built up
It is called alluvium which is very fertile meaning crops can grow on it

Question 23

How are levees formed

Answer 23

When rivers flood it loses the velocity and therefore the energy, so it deposits, the big load first

Question 24

What happens during a low flow

Answer 24

The river doesn’t have any energy to carry its load so it deposited on to the river bed
If the velocity comes really slow the amount of water 💦 falls and the river may dry up altogether
If load is deposited on the bed and not washed away at the end of the season the river bed can rise and therefore floods are more common

Question 25

How are floodplain protected from floods

Answer 25

Levees, they can be artificially strengthened and raised

Question 26

What are rivers used for in MEDCs

Answer 26

Cattle for grazing Factories, water for cooling Housing

Question 27

What are some river uses in LEDCs

Answer 27

The floodplain provides good patty for rice 🍚 | The alluvium provides good fertile land for crops

Question 28

What is a river

Answer 28

An important resource to everyone so that any changes to them have to be sustainable for future generations

Question 29

What are other uses of rivers

Answer 29

Water- irrigation and water supply Power- hydroelectricity and water mills Food- 🐟 is main source of protein in LEDCs Transport- 🚂 and roads Waste outlet- effluent is drained out to 🌊

Question 30

What are five physical reasons for floods

Answer 30

Heavy rainfall= surface runoff= flash flood Prolonged rain eg. monsoon= saturates the ground= long, slow flood Melting of snow ❄️ or glaciers= increased discharge in spring= rivers overflow Impermeable rock or clay soil= infiltration cannot happen, increased surface runoff= area of high risk of regular floods Frozen ground= when precipitation cannot be infiltrated into ground, more surface runoff= area high risk of regular floods

Question 31

Give four more human factors that contribute to floods

Answer 31

Deforestation= less roots support for soil, less water being used up by 🌱, 🍁 to break big rain droplets=more surface runoff = more chance of flooding Urbanisation= more tarmac, concrete and impermeable surfaces= more surface runoff= more chance of floods Narrowing a channel eg. building a bridge= river has less water capacity= more chance of flooding Building of levees (embankments)= provides short term protection, but...= if flooding exceeds it= severe flash flood

Question 32

Give some detail about the River Derwent flood

Answer 32

Happened in 1999 The River Derwent, Yorkshire, experienced worst flood in 70 years Some areas effected where 1.5 meters deep in water and two main roads had to be closed

Question 33

What are the physical reasons the River Derwent flooded

Answer 33

Heavy rainfall, from 28th February to 11th of March 125mm of rain fell over North Yorkshire moors Already saturated ground, from recent events Time of year, ❄️ was melting which added on to discharge

Question 34

What are the human reason the River Derwent flooded

Answer 34

Peat removal, less soil to soak up water as peat acts like a sponge New building, on the floodplain eg. new estate in Malton, so increased surface runoff

Question 35

What are three positive impacts and three negative 👎 four impacts of floods

Answer 35

Replenishes water 💦, leaves sediment eg. alluvium and silt on floodplain which fertilises the floodplain soil, countries such as Bangladesh and Egypt are dependent of floods Spreads water born diseases, can destroy buildings and infrastructure eg. roads and railways 🚃, can leave animals and people homeless or they can even drown, destroy crops on the floodplain

Question 36

What are two positive and negative effects of flooding

Answer 36

Fish can breed in standing floodwater, in dry areas floods can bring relief from drought providing drinking 💦 for animals Floods can bring chemicals and sewage into the local rivers polluting them, wild 😜 animals may lose their homes 🏡 or drown