Paper 1 - Section C, Uk River Landscapes Flashcards
What does fluvial mean
River related, for example fluvial flooding is flooding caused by a river
What does pluvial mean
Rainfall related, for example pluvial flooding is flooding cause by heavy or prolonged rainfall
What are the 3 actions performed by a river
- Transportation (movement of eroded materials from one location to another)
- Erosion (wearing away and removal of material by a moving force)
- Deposition (when material being transported by river is dropped due to river losing energy)
What are the 4 processes of transportation
- Traction - moving largest and heaviest material (boulders rolled along river bed)
- Saltation - moves smaller stones by bouncing them along river bed
- Suspension - carrying very fine material within water (floats in river)
- Solution - dissolved load (only occurs with certain type of rock eg chalk)
What are the 4 processes of erosion
- Abrasion - when the load river is carrying repeatedly hit against bank + bed causing material to break off
- Hydraulic action - sheer force of water hitting bed and banks
- Attrition - stones carried in river hit against each other over time causing bits to break off and reduce in size
- Solution - when river flows over certain stone (eg chalk) they are solvable and dissolve and become part of water
What is deposition
- occurs when river dumps or leaves behind any material it was carrying
- deposits heavy material first as requires more energy
- smaller load can be transported further downstream
Why does a river deposit its load
When there is a slowing in the speed of the flow due to a bend in the river (meander) or a change in the gradient of the slope
What landforms form in the upper course of a river
- waterfall
- gorge
- interlocking spurs
What landforms form in the middle course of a river
- meanders
- flood plain
What landforms form in the lower course of a river
- meanders
- floodplains
- ox bow lakes
What is the discharge of a river
The amount of water that passes a given point on a stream or riverbank in a given amount of time
How are waterfalls formed
- A layer of hard rock overlays a layer of softer rock
- as river passes over softer rock it is able to erode it at a faster rate forming a step in river bed
- River now flows vertically + force of falling water results in plunge pool
- Rocks trapped in plunge pool are swirled around causing abrasion of the sides of the pool
- With little support the hard rock over hangers collapses and collapsed rock adds more rocks to plunge pool
How are ox-bow lake formed
- Erosion happens on outside of a meander bend, because fastest flow of river so load is Theon at bank and causes lateral erosion through abrasion and hydraulic action
- Deposition occurs on inside bend as a result of slow flowing water and lower energy forming a slip off slope. Neck of meander will eventually narrow due to erosion forming a river cliff
- Eventually neck of meander keeps narrowing until it’s completely broken (usually due to flood).forms a new straighter channel cutting off the meander leaving an ox-bow lake
What is abrasion
Rocks carried along a river wear down the river bed and banks
What is alluvium
A sediment deposited by a river when it floods
What is attrition
Rocks being carried by the river smash together and break into smaller, smoother and rounder particles
What is a channel
The main water course
What is channel straightening
Removing meanders from a river to make it straighter
What is the confluence
Where a tributary joins a large river
What is solution (corrosion)
When the river flows over limestone or chalk, the rock is slowly dissolved
What is the cross profile
A cross section of a river channel or it’s valleys
What is a dam
A barrier built across a valley to interrupt river flow
What is deposition
Occurs when material being transported by the river is dropped due to the sea loosing energy
What is a drainage basin
An area of land drained by a river and its tributaries
What is embankment
Artificially raised river banks often using concrete walls
What is erosion
Wearing away and removal of material by a moving force
What is an estuary
Tidal mouth of a river where it meets the sea - wide banks of deposited mud are exposed at low tides
What is a flash flood
A very sudden flood event resulting from a torrential rainstorm