Rivers Flashcards
What is a drainage basin?
A drainage basin is an area of land drained by a river nd it’s tributaries
What does the long profile of a river show?
Shows how a rivers gradient changes as it flows from the source to its mouth
What does the cross profile show ?
The cross profile of a river shows the shape of the river Chanel
Where does vertical erosion take place ?
In the upper course of the river
Where does lateral erosion take place?
In the middle to lower course of the river
Where is a v shaped valley located?
In the upper course
What is erosion ?
The gradual removal of rock from a rivers banks and riverbed
4 types erosion
Hydraulic action- force of the river causes air to become trapped in cracks and crevasse causing the pressure to build
Solution- soluble particles and minerals are dissolved into a river.
Abrasion-rocks carried along by the river wear down river bed and banks
Attrition- rocks carried by river smash together breaking into smaller and smoother pieces
What are interlocking spurs?
The upper course of the river has less energy so it eroded the easier path . This forms spurs that appear to interlock
4 types of deposition and transportation…
Suspension- fine and light material is carrried along in the water
Solution- minerals are dissolved in water and carried along in the solution
Saltation- small pebbles and stones bounced along the riverbed
Traction- big boulders and rocks rolled along the river bed.
Factors leading to deposition include…
Velocity of water slowing ( the energy the river has )
Shallow water
When the volume decreases
At the end of a rivers journey at the mouth
Formation of a waterfall
Step1-hard rock over soft rock, soft rock is eroded
Step2- after a while a plunge pool is created
Step3- over time the hard rock overhang is unsupported, and it falls
Step 4- overtime the waterfall retreats upstream forming a gorge .
What’s helicoidal flow?
Corkscrew motion in a river caused by uneven riverbed.
What’s a meander?
Where’s it found ?
How’s it formed?
A bending curve in the river
Found in middle / lower course
Formed due to erosion and deposition
What’s the Thalweg line?
A line of fastest flow in a river Channel
What is an oxbow lake?
A semicircular area that represents the former course of a meander
What’s a floodplain?
Area of land adjacent to the river that allows the river to overflow once banks have reached maximum capacity
What’s a levee?
Natural raised riverbanks
What’s an estuary ?
Tidal part of a river where freshwater from the river merged with saltwater from the sea.
What’s a delta?
A flat area of sand and silt built up out at sea, usually by the river mouth where velocity has dropped, causing the sediment to sink.
RIVER TEES CASE STUDY. Name source -, location
The river tees is located in the NORTH-EAST of England
tThe source of the river is the NORTH PENNINES.
Flooding occurs when…
A river burtsts it’s banks and overflows onto the surrounding land.
Human causes of flooding…
Urban land use
Deforestation
Physical causes of flooding …
Relief
Prolongued rainfall
Heavy rainfall
Geology
How can rainfall/ discharge be put into a graph..
Flood hydrographs
Ways to stop flooding (types of engineering)
Hard engineering
Soft engineering
Examples of hard engineering
Dams and reservoirs
Channelisation (channel straightening)
Embankments
Flood relief Channels
Examples of soft engineering…
River restoration
Afforestation(interception)
Floodplain zoning
Flood warning system
What does a dam/ reservoir do?
Advantages…
Disadvantages
Holds water and releases it downstream in a controlled manner.
Advantages- source of drinking water, effective against floods, boosts tourism
Disadvantages-often very expensive, can be a waste of money
What’s channel straightening (hard engineering)
Advantages….
Disadvantages….
-Meandering section of a river engineered to create a widened and straightened course
Adv- reduces flood risk, by moving water out of an area quicker, less friction with river banks (reduces erosion)
Disadvantages- £5.8 million dredging
What’s an embankment….
Advantages
Disadvantages
Artificially raised river bank—-> More water held in the Chanel
Advantages- cheap, provide habitat for animals
Disadvantages- deprive people of easy river access, displace animals from river banks
What’s flood plain zoning (soft engineering)
Advantages…
Disadvantages…
Using zones to categorise where buildings are built.
Advantages- low cost, provides Greenspace in uk towns
Disadvantages- habitats may be destroyed due to increased building on greenfield sites
How’s a meander formed?
1) Current is faster on outer bend, so more erosion takes place on the outer bend
2)current is slower on the inside bend as river channel is shallower
3) so eroded material is deposited on inside bend, forming slip of slopes
What does planting trees do ( soft engineering)
Adv
Disadvantages
Increased interception of rainwater.
Advantages- less water into river
Disadvantages- less land available for farming
What does planting trees do ( soft engineering)
Adv
Disadvantages
Increased interception of rainwater.
Advantages- less water into river
Disadvantages- less land available for farming
Formation of a leve (4)
-River floods, all sediment comes out of channel onto sides.
-larger rocks and boulders deposited first because velocity slows.
-after the floods, the sediment and rock remain in place.
-as a result, raising it
What’s the case study for a river flood relief channel?
What river is it a relief channel for?
How much did it cost?
Jubilee river flood relief Chanel
£110 million
Why was the scheme required?
The area was a rich area and had lots of high value properties that flooding was damaging
Drawbacks of the jubilee flood management scheme?
Economic - Ended up costing £330 million
Social- Disrupted people using the river for leisure (paddle boarders)
Environmental - concrete weird made river look unattractive , disrupted environment
Benefits of the jubilee river management scheme… (environmental,social, economic)
Environmental- Stops flooding of the natural habitats (been opened over 30 times)
Social- residents of Eaton and Windsor pleased as it reduced risk of homes flooding.
Economic- insurance companies pleased as it reduces risk of a big payout
How’s a floodplain formed?
1)Erosion / deposition removes any interlocking spurs and creates an area of flat ground on either side of river channel.
2) when river floods, velocity slows, and sediment is deposited on the floodplain.
3) after a while of this process repeating, the height of the floodplain increases.
