Paper 2: River Processes and Pressures Flashcards
What are the 3 sections of a river?
Upper course, middle course, lower course
What are some key features of the upper course of a river?
- The source of the river
- Lots of little tributaries
- Thin and shallow
- Lowest volume of water
- Slow rate of water travelling due to friction
- Not much erosion due to slow water
What are some key features of the middle course of a river?
- Rounder in shape and deeper
- Higher volume of water
- The area around it is often a floodplain
What are some key features of the lower course of a river?
- The mouth of the river
- Deep and wide
- Has levees (build up of sediment on its banks)
- Less friction and so faster rate of water travelling
- More erosion due to fast water
- The most deposition happens here
What are the 4 river transportation processes?
- Solution
- Suspension
- Saltation
- Traction
What is solution?
Chemicals are dissolved in the river water
What is suspension?
Particles and small rocks are light enough to float within the water
What is saltation?
Pebbles and small rocks which are too heavy to be suspended bounce along the river bed
What is traction?
Large rocks are rolled along the river bed
What is river deposition?
The dropping of the river’s load when the water decreases in speed
What landforms are found in the upper course of the river?
Erosion is the predominant river process
- Waterfalls
- Interlocking spurs
- V-shaped valleys
What landforms are found in the middle course of the river?
Mixture of erosional and depositional landforms
- Gorges
- Meanders
What landforms are found in the lower course of the river?
Deposition is the predominant river process
- Floodplains
- Ox-bow lakes
- Estuary
How are interlocking spurs formed?
These are found in the upper course of the river where the water doesn’t have a lot of energy so isn’t very powerful. The low energy means the water isn’t strong enough to erode resistant rocks in the spur. Instead, the river re-routes and curls around them.
How are waterfalls formed?
- In an area where a river flows over an area of hard rock and soft rock, the soft rock erodes more quickly
- The soft rock erodes away around
the hard rock over time - The soft rock continues to erode, undercutting the hard rock - The hard rock is left suspended in the air as an overhang - The rotational movement of the water quickens erosion, creating a deep plunge pool.
- Due to the force of gravity, the unsupported overhang collapses - The broken up rocks fall into the plunge pool, which act as tools for erosion and further deepens the plunge pool
- This repeats, causing the waterfall to retreat upstream
What is a gorge?
As the waterfall retreats upstream, it leaves a steep valley carved into the rock with the river running along the base