Paper 1 section C - Rivers Flashcards
What is a river
A large natural stream of water flowing in a channel to the sea, a lake, or another stream.
What is a long profile
A long profile shows the gradient of a river as it journeys from source to mouth.
Parts of a river
Source
Mouth
Tributary
Confluence
Main river channel
Drainage basin
Watershed
What is the source of a ricer
The place where a river starts in its upper course
What is the mouth of a river
The place where a river meets the sea
What is the cross profile
The cross profile shows you what a cross-section of the river looks like
Draw the cross profiles of upper, middle and lower course
https://igcsegeography.files.wordpress.com/2015/12/cross-profile-of-a-river.png
What does the shape of the valley and channel of a river depend on
The shape of the valley and channel changes along the river depending on whether erosion or deposition is the dominant process
Describe how a river changes from source to mouth
Rivers begin in upland areas and flow downhill.
Near the source, the long profile of a river shows a steep gradient.
It gradually gets lower and less steep until the river reaches sea level.
The river has a V-shaped cross profile in the upper course.
By the time the river reaches its lower course, the valley is wide and flat
Characteristics and processes happening in Upper Course
Vertical erosion with Hydraulic action,( abrasion and attritio)n - This deepens the river valley and channel making it V-shaped. These are the dominant processes in the upper course
Transport: Traction and saltation at high flow. Load size is large and angular
Deposition: Large boulders deposited
High turbulence causes the rough, angular particles to be scaped along the river bed, causing intense downwards erosion
V shaped valleys
Change: High relief, steep gradient, waterfalls and rapids
Characteristics and processes happening in Middle Course
Channel is deeper and wider
Vertical erosion decreasing in importance, more lateral erosion (attrition, abrasion and solution). The lateral erosion widens the river valley and channel during the formation of meanders and deposition
Suspension is the main transportation type occurring here
Load becomes smaller and less angular
Deposition: More deposition on inside bend of meanders
CHANGE:
Discharge has increased
Tributaries have joined
Gradient of long profile is concave
Characteristics and processes happening in Lower Course
Channel is at its widest and deepest, and may be tidal
The lateral erosion widens the river valley and channel during the formation of meanders
Deposition more important than erosion (very little erosion, only lateral erosion)
Deposition is now the main fluvial process. Fine material deposited
Transport:
Suspension and solution. Large amount of load but the size is very small and very rounded
Change: Area closest to river mouth, with low-lying land. Erosion is now lateral erosion at meanders. Gradient almost flat.
Where is vertical erosion dominant
Vertical erosion is dominant in the upper course of the river
Where is lateral erosion dominant
Lateral erosion is dominant in the middle and lower courses of the river
Erosion can be _____ or ______ - both types happen __________ but one is usually _______ at different points along the river
Erosion can be vertical or lateral - both types happen at the same time, but one is usually dominant at different points along the river
Define dicharge
Discharge is the volume of water passing through a given point on the river. It is measured in cubic meters per second (cumecs).
Formula for discharge
Discharge = velocity x cross-sectional area
Explain why dicharge increases downstream
Discharge increases downstream since tributary streams join the main river and add their volume of water to it.
In the upper course, the small channel means lots of friction, which slows the water down.
In the lower course, the channel is broad and deep so water has little contact with the banks and velocity is much higher. Speed is boosted by additional discharge from tributaries.
State the types fluvial processes
Erosion
Transportation
Deposition
Types of erosion
Hydraulic action
Abrasion
Attrition
Solution
Vertical erosion
Lateral erosion
What is vertical erosion
Vertical erosion is a type of erosion that deepens the river valley and channel, making it V-shaped
What is lateral erosion
Lateral erosion is a type of erosion which widens the river valley and channel
What is fluvial
Fluvial means to do with a river
What is a fluvial process
A fluvial process is the motion of sediment and erosion or deposition on the river bed.
Explain the process of hydraulic action
This is when the sheer force of fast-flowing water hits the river banks and river bed and forces water into cracks.
This compresses air in the cracks.
Repeated changes in air pressure weaken the channel, causing rock particles to break way from the river channel
What is hydraulic action responsible for in the upper course of the river and lower course of the river
Hydraulic action is responsible for vertical erosion in the upper course of a river.
In the lower course, it contributes to lateral erosion of the banks, especially when fast-flowing water hits the outside bend of the meander.
Lateral erosion is partly responsible for the migration of meanders across the floodplain.
Explain the process of abrasion
Small boulders and stones may scratch and scrape their way down a river during transport, thereby wearing down the river banks and bed.
Stones which have fallen into the channel quite recently will be angular and have sharp, jagged edges.
These are particularly effective tools of abrasion.
What is hydraulic action responsible for in the upper course of the river and lower course of the river
Ongoing abrasion is responsible for both vertical erosion and lateral erosion of the channel.
The faster a river’s flowing, the more _____ happens
The faster a river’s flowing, the more EROSION happens
Explain the process of solution
Solution refers to the dissolving of rocks such as chalk and limestone.
Rivers travelling over these rocks will erode them in this way.
Where does solution occur
Solution occurs in streams running through rocks such as chalk and limestone.
Describe the process of attrition
Eroded rocks picked up by the river crash into each other and break into smaller fragments.
Their edges also get smoother and more rounded as they rub into each other
The further material travels, the more it is eroded - attrition cause particle size to decrease from a river’s source to its mouth
