Rivers Flashcards
What is the source of the river?
Where the river begins
What is the drainage basin?
The area from which water drains into a river
What is the water shed?
An imaginary line that separates two drainage basins
What is confluence?
The point where 2 rivers join together
What are tributaries
Smaller rivers which join to the main river
What’s the flood plain?
Land that floods when a fiver overflows
What is the mouth of a river?
Where the river flows into the sea or lake
What’s the river bed?
The bottom of the river channel
What’s the river banks
The sides of the river channel
What’s the river long profile?
Shows how a rivers gradient changes as it flows from its source to its mouth
Lost some characteristics of the upper course:
- steepest part of the river
- small channel but fast flow
- high energy levels
- river erodes bed
- downward erosion
- v shaped valleys
Name some characteristics of the middle course?
- slower flow
- less steep river banks
- more tributaries making river wider
- flood plain starts to develop
Name some characteristics of the lower course:
- valley sides are gone
- large floodplain
- slow movement/flow
- deposition is main process
What is erosion?
The gradual removal of rock from river banks and bed
What’s corrosion/abrasion?
The bed and banks are worn down by the rivers load - rocks hit banks at high velocities to break the banks and bed away
What’s attrition
The load carried by the river hit each and are broken down into smaller smoother rocks
What’s solution?
The chemical action if the river water, the acids in the water slowly dissolve the banks and bed of the river
What’s hydraulic action?
When the force of water is against the bed and banks and eroded it
Name some ways the rates of erosion can be affected
Discharge, velocity, gradient , rock resistance/type
What is the bed load?
The material carried by a river as it moves
What is the transportation process of suspension?
Fine light material carried along the water
What is the transportation process of solution?
Minerals are dissolved in the water and carried along in water
What’s the transportation process of traction?
Large boulders and rocks rolled along the river. Bed
What’s the transportation process of saltation?
Small pebbles and stones rolled along the river bed
What’s a waterfall?
A geographical formation where flowing water rapidly drops in elevation as it flows over a steep region/cliff
How do waterfalls occur?
When rivers flow over different types of rock, the soft rock wear away faster than the hard rock. In time a step develops over which the river plunged as a waterfall, water also cuts away rock behind the waterfall, this causes the fells to move back and leave a gorge as it goes.
What’s the water fall cycle
Soft rock worn away -> hard rock undercut -> plunge pool deepens -> hard rock collapses -> waterfall
Moves back ->
What’s the thalweg?
The line of fastest flow/velocity
What is a meander?
A bend in the water course of the river
The the river cliff in a meander?
Where erosion happens and undercutting occurs On the outer bend
What’s the slip off slope?
Deposition on the inner bend
Where do meanders occur?
In the middle course - in a wider and deeper channel and an open area with a floodplain
How does a meander occur?
When there are changing velocities in the middle course and the water flows in a spiral which causes variation in velocity across the channel which creates a thalweg and where there is most an energy in the outer bend erosion processes occur like abrasion and hydraulic action and a river cliff forms however in the inner bend where there is least energy deposition occurs and forms a slip off slope, over time more is eroded and deposited and a meander is formed
What’s an ox bow lake?
A horseshoe area that represents the former course of the river going through a meander
How does a ox bow lake form?
The thalweg in the outer bend of a meander causes erosion which cause the neck to narrow, then during s flood of when there’s a lot of water, it breaks through the neck and so stops going round the meander as water always takes the fastest route, then deposition occurs which blocks the Meander forming an oxbow lake
What is capacity?
Maximum amount of things a river can carry - overall weight
What is competence?
The maximum size of a thing a river can carry
How do levees form
In a flood larger material is deposited on the banks and over many floods it builds up to be levees
What’s an estuary
The tidal part of the river where the channel broadens out as it reaches the sea
What’s a tidal bore?
Huge waves that move up the river than can damage vegetation and banks
What are mudflats?
Laters of mud from depositions where there’s less velocity
What’s a delta
A flat area of sand and silt built out into the sea
How do deltas occur?
When a particular river is carrying a large load and it reaches the sea the velocity slows and drops the load
What’s the valley like in all the courses?
Upper course - v shape
Middle course - u shape
Lower course - much wider u shape [ - that shape on turned 90 degrees
What are the human causes of flooding?
Deforestation, farming, channelisation, urbanisation,
What are the physical causes of flooding?
Snow melting, rain, impermeable rock
What’s interception?
When water is absorbed by vegetation
What’s infiltration
When water is absorbed into the ground
What’s transpiration
Where plants evaporate water from leaves
What’s percolation
Some water goes deeper in the ground and is slowly transferred back to the river or sea
What’s through flow
When water infiltrated the soil and moves more slowly back to the river than surface run off
What’s groundwater
Water that has infiltrated the ground and is found in cracks and spaces in the soil and rocks
What’s surface run off
Water that directly flows back into the river
In hydrography a what is the base flow?
The starting and finishing flow of the river either side of the increased discharge
What’s lag time
Time between peak rainfall and peak discharge
What’s the rising limb?
The increasing discharge as water enters channel
What’s the falling limb
Fall in discharge back to base flow
What is a dam
Built to control discharge and holds back water, very expensive but can be a source of drinking water
What’s afforestation
Planting trees to slow down the flow of water towards the river channel and allow more interception
What’s levees or embankments
Increase the maximum area of the river channel allowing it to hold more water
What’s floodplain zoning
Consider the flood plain and try to build in areas far or elevated from the river
What’s channelisation
Building concrete banks and straightening the river to reduce friction and allow the water to flow quicker
What’s a flood warning system
Allows evacuation of areas likely to flood and reduces damage as people can prepare
What are retention ponds
Ponds that allow runoff to me temporarily stored
What are energy levels like in upper course
A lot of gravitational potential energy so vertical erosion, not enough energy to carry big rocks in water so rolled along bed
What are middle course energy levels like
More kinetic energy do more transportation
Less gravitational potential energy so lateral instead of vertical erosion
What’s energy in the lower course like
No gravitational potential so mainly lateral erosion a lot of deposition due to slow velocity
