Rivers Flashcards
Define floodplain
Wide, flat, floor of a river valley over which the river floods during heavy times of rainfall
Where does solution occur?
Solution occurs throughout the river, but especially in areas with limestone rock
Define levee
Natural ridge of material deposited along the banks of a river in its old stage
Which stage do meanders occur in?
Middle course
Where does dendretic drainage occur?
Areas with uniform rock types -> equal erosion
What stage of the river do oxbow lakes occur in?
Old age stage
What fluvial process (/s) is present in the old age stage of the river?
Deposition
Give an Irish example of a flood plain
All rivers in Ireland eg. River Shannon, Co Limerick and Cavan
Define suspension
Fine, light material is carried along by the river
What is the gradient of the river in the mature stage?
Gentler
What stage of the river do floodplains occur in?
Lower course
Draw labelled diagram of watershed
See notes
Explain the formation and erosion of waterfalls (30m)
See notes
What is the gradient of the river in the youthful stage
Steep
Which processes form meanders
Erosion and deposition
Explain the process of solution
Some types of rocks like limestone dissolve in the slightly acidic water of the the river, gradually removing material from riverbed and banks
What is the speed of the river in the youthful stage
Fast
What does trellis drainage look like?
Tributaries join river at right angles
What are lacustrine deltas?
Deltas where rivers flow into lakes
What are some key landforms of the youthful stage of the river?
- V-shaped valleys
- Rapids
- Gorges
- Waterfalls
- Interlocking spurs
What does dendretic drainage look like?
Like tree branches, tributaries flow into the main river channel at right angles
Which processes form a delta
Deposition and erosion
Where does saltation occur?
In the middle course, where the river starts to lose energy but still moves smaller particles
Define traction
Large boulders and rocks are rolled along riverbed
Explain the formation of a delta
- Flat area of sediment is deposited at the mouth of the river
Define watershed
A highland area that separates one drainage basin from another
Explain the process of traction
Large, heavy rocks and boulders and rolled along the riverbed by the force of the water
What stage of the river do levees occur in?
Lower Course
Explain formation of alluvial fans and river braids
Build up of sediment on flat/gently sloping riverbed forms alluvial fans. River bed splits into streams flowing around alluvial fans called river braids
Explain the process of saltation
Small pebbles and stones are bounced along the riverbed as the river doesn’t have enough energy to carry them all the time, so they move in short bursts
Explain formation of oxbow lakes
- Oxbow lakes are relics of former meanders and are also known as cut-offs
- When a meander becomes so pronounced, that during a flood, the river cuts through the narrow neck of the bend to form a new straighter channel
- The abandoned meander loop is then isolated from the main river, creating a crescent-shaped lake
- Over time, sediment and vegetation accumulate in the oxbow, gradually sealing it off, it dries out and transforms into a mort lake
What fluvial process (/s) is present in the mature stage of the river?
Erosion and deposition
Discuss how humans interact with surface processes: The impact of flood control measures on rivers (30m)
See notes
Where does suspension occur?
In the middle and lower course
Define bedrock
Solid rock that lies beneath soil
Draw diagram showing river erosion
See notes
What is the shape of the valley of the river in the youthful stage
V-shaped, narrow, deep
What are some key landforms of the old age stage of the river?
- Oxbow lake
- Delta
- Levee
- River braiding
- Flood Plain
Define drainage patterns
Shapes created by rivers on the land
What is the speed of the river in the mature stage?
Slower than youthful stage due to reduced energy
Explain the process of attrition in river
The load in the river colliding with each other, breaking the rocks into smaller, smoother and rounder pieces
Be able to identify drainage patterns from pictures
N/A
What is the shape of the valley in the old age stage of the river?
Very wide, flat, flood plain
What stage of the river do alluvial fans and river braids occur in?
Middle course
Explain the process of solution
Some materials, like limestone and chalk, are dissolved in the water and carried invisibly as the river water reacts with certain rocks, breaking them down chemically
Define alluvium
Fine particles in river eroded by attrition
What river processes form floodplains?
Deposition
What is fluvial process (/s) present in the youthful stage
Erosion
Define saltation
Small pebbles and stones are bounced along the riverbed
What does deranged/chaotic drainage look like?
No set pattern
Where does deranged/chaotic drainage occur?
Areas that once had glaciation eg. Marshy areas/swamps
How can we observe suspension happening?
The water looks brown and muddy
What does radial drainage look like?
Like spokes of a wheel, tributaries flow down the side of a mountain
What is the speed of the river in the old age stage
Slow moving
Which processes form alluvial fans and river braids
Deposition
Explain the process of hydraulic action
The sheer power of the water pushes into cracks in the rock compressing air and causing the rock to weaken and break apart over time
Give an Irish example of alluvial fans and river braids
Ballisodare river, Co. Sligo
Which processes form levees?
Deposition
Where does trellis drainage occur?
Areas where valley is soft rock and eroded quicker
Give an Irish example of a levee
River Moy, Co Mayo
Where does radial drainage occur?
Mountain sides
Give an Irish example of a delta
Shannon Estuary, Co. Limerick
What factors affect drainage patterns?
- Rock type
- Marsh land
- Glaciation
- Karst
Explain the process of suspension
Fine particles like sand, silt and clay are carried (suspended) in the water as the river has enough energy to keep them moving without touching the riverbed
What are some key landforms of the mature stage of the river?
- Meander
- Floodplain
- Levee
- Alluvial fans and river braids
Explain the process of abrasion
The river carries sediment like sand, pebbles and rocks which scrape and wear away the riverbed and banks, acting like sandpaper
Give an Irish example of an oxbow lake
River Moy, Co Mayo
Explain the formation of one landform of erosion and one landform of deposition using diagrams (30m)
See notes
Define meander
Pronounced c-shaped loops that develop along the middle course of a river
Give an Irish example of a meander
All rivers in Ireland eg. River Shannon, Co. Limerick and Cavan
Where does traction occur?
In the upper course of the river where water has most energy
Define differential erosion
When one area/rock is eroded at a faster rate than another area/rock
Define solution
Minerals are dissolved in the water - chemical change
What are marine deltas?
Deltas where rivers flow into seas
What is the shape of the valley of the river in the mature stage?
Wide, gently sloping sides
Which processes form oxbow lakes
Lateral erosion, deposition, neck narrowing, cut off
What is the gradient of the river in the old age stage?
Very gentle/flat
