River

Question 1

What is river mouth

Answer 1

Where the river meets the sea

Question 2

Tributary

Answer 2

A small river that flows into a bigger river

Question 3

Confluence

Answer 3

Where two rivers join or meet

Question 4

River long profile

Answer 4

The course that river takes from its source to mouth
The long profile is often split into upper course and lower course
The upper course is near the source and is normally found in mountainous areas
The lower course is near the mouth and on much flatter ground nearer sea level
Show the changed in the steepness of the river from source to mouth

Question 5

Define erosion

Answer 5

The break down of rocks by moving water, ice and wind, which then transported the eroded material away
Th process of wearing something away

Question 6

Describe hydraulic action

Answer 6

Waves have great energy which is released as they break against the cliff
Waves trap air in cracks in the rock
This air is compressed by the waves, eventually causing them to crack
This happens in river bank and bed

Question 7

Describe attrition

Answer 7

Particles carried by the waves crash against each other and are broken into smaller particles
It takes place when the rocks on the bed of the river are rolled along and they collide
-> the average size of the rock particle (sediment) becomes smaller as it moves down toward the river mouth

Question 8

Describe solution (corrosion)

Answer 8

Some minerals are dissolved into solution by the weak acids found in river water

Question 9

Describe abrasion (corasion)

Answer 9

The rivers’ load crashing and rubbing into rivers’ bank and bed causing the removal of particles of rock

Question 10

What is river source

Answer 10

Where rivers begin in the upland

Question 11

Describe vertical erosion

Answer 11

Happens in the upper course, water flows quickly through a narrow channel with a steep gradient -> it cuts downward
Results in V shape valley and interlocking spurs
Increase depth

Question 12

Describe lateral erosion

Answer 12

Increase a river’s width

Happens in the lower course

Question 13

Describe 4 method of transportation

Answer 13

Traction
Saltation
Suspension
Solution

Question 14

Describe traction

Answer 14

Large pieces of load rolling along a river bed

Question 15

Describe saltation

Answer 15

Smaller loads bouncing along a river bed

Question 16

Suspension

Answer 16

Very small pieces of load being carried in a river flow

Question 17

Solution

Answer 17

Dissolved pieces of material being transported in a solution

Question 18

What is load

Answer 18

Material that is transported by a river, if the material is being transported along the bed, it is known as bedload
If it is transported in a river flow, it is often called suspended load

Question 19

Describe river deposition

Answer 19

River loses energy -> start to drop/deposit its bedload and suspended load
Heavier materials deposit first and as the river continues to slow down, the smaller material will get deposited
Takes place in the river channel, inside of a river meander, on its floodplain or on its delta
Happens when there is less water or the current slow down

Question 20

When does river velocity slow down

Answer 20

Gradient decrease
River channel : rougher and shallower
River meets a large body of water (sea,lake)

Question 21

What is river basin

Answer 21

All the landform are found within a river basin (drainage basin)
All precipitation that falls within a river basin will make its way towards the river channel

Question 22

What is watershed

Answer 22

The dividing line between river basins

Question 23

What is discharge

Answer 23

How many cubic metres of water is passing every second

As each tributary join the main river channel, the river discharge will increase

Question 24

What is river cross section

Answer 24

Drawn across the rive valley
In the upper section - steep-sided and narrow
In the lower section - gentle sided and wide

Question 25

Describe the upper section of a river

Answer 25

Narrow V shaped valley
Narrow river channel
Vertical erosion dominates
River channel completely fill the valley
Full of large stones
Smaller discharge, flow slower

Question 26

Describe the lower section

Answer 26

Wide valley and large channel
Often a floodplain will be found beside the river channel
Smaller and rounder rock
Lateral erosion dominates, deposition takes place
River channel become larger as river discharge increase

Question 27

Formation of v shape valley

Answer 27

Formed in the upper course where the river channel is narrow and vertical erosion is dominant
River erodes downward due to vertical erosion, put almost all of its energy towards cutting down to the base level (abrasion, hydraulic)
Overtime, the side of the valley are weaken by weathering
Steep sides causes material to fall into the river and is transported downstream by the river

Question 28

Formation of interlocking spur

Answer 28

As the river flows through the valley it is force to swing from side to side around more resistant rock
The river continues to cut down vertically while meander around these resistant rock, creating interlocking spur

Question 29

Formation of rapids

Answer 29

Upper course
Form when have a layer of hard and soft rock
Layer of soft rock erode quicker than the layer of hard rock
-> makes the bed of the river uneven creating rough turbulent water
Eventually, a waterfall may develop when the soft rock is eroded

Question 30

Problems of rapids

Answer 30

Ships cannot travel up and down rapids
Hard to build bridges across them
Dangerous if people fall into them

Question 31

Formation of waterfall

Answer 31

Upper course
Band of harder rock lies over a softer ones
Often starts as rapid
Water flows over the edge of harder, more resistant rock and erodes the river bed and the bottom of the waterfall
This makes a plunge pool
Erosion gradually undercuts below the hard rock bs the soft rock is eroded more easily
Undercutting -> overhang of hard rock -> too heavy to be supported -> collapse into the plunge pool
The whole process start again -> retreats upstream toward the source
A steep sided valley know as gorge is left behind as the process continues and waterfall retreats

Question 32

Formation of potholes

Answer 32

Found in the river bed

Load carried by the river is washed around in a circular motion causing vertical erosion, creating a cylindrical hole

Question 33

Formation of deltas

Answer 33

River meets sea -> velocity suddenly reduces
River that carries a large amount of sediment loses its energy and drop the sediment it is carrying
-> much of the river load is deposited at the mouth of the river
If the river deposits its material faster than the sea erode it -> delta starts to develop
Deposition -> main river channel is block and small island forming in the river mouth, forcing water to find alternative routes to the sea by splitting into several smaller channels called distribution
Deltas have fertile soil and good for farming

Question 34

Formation of Levees

Answer 34

Forms on edge of the river channel in its lower course
Formed by river depositing material when floods
River flood -> velocity of the river traveling to the flooded floodplain suddenly falls
-> immediately deposits its largest load -> build up around the sides of the river forming raised banks known as levees
Finer material such as silt and fine clay continue to flow further over the floodplain before they are deposited
Overtime, after many flood, these embankment begins to grow in size and become more stable

Question 35

Formation of floodplain

Answer 35

The area on either side of a river that the river may flood into when they exceed bank-full discharge
Very fertile area due to the rich alluvium (mineral rich load) deposited by the floodwater