Rivers Flashcards
What is river discharge?
the amount of water passing a specific point at a giventime.
What is river discharge measured in?
Cubic meters per second or Cumec
What 2 factors affect the amount of discharge?
Volume – the amount of water in the river
Velocity – the speed of the river
How does discharge as the river moves downstream?
The dischargeincreasesbecause of the increase volume as more tributaries join the river.
Why does river discharge increase as you go downstream?
the channel gets wider and deeper downstream and so the river can hold more water.Thevelocity/speedofthe river also increases as you move downstream. There is more water in the river in the channel because tributaries are adding more watertothe river.
How does the UK’s weather and climate affect river processes?
Winter would have the most erosion.There is more rain and therefor more water to erode the river and so more Hydraulic Action and Abrasion on the river bank and bed. Cold conditions in the winter will cause more freeze thaw to occur.
How does the UK’s weather and climate impact on river landforms?
Levee-this is a raised river bank. It is made when the river repeatedly floods. So heavy rain makes this feature.
What is a levee made?
A levee is a lower course feature
It is created by repeated flooding
When the river floods, the water moves out of the channel
The energy levels in the water all rapidly when this happens.
The river drops its load on the river bank The heaviest (bigger bits of load) material will be dropped later, on the flood plain
After many floods the levees are formed.
What is a flood plain?
Flood plan is a lower course feature.
It is made by meander migration
As the meander moves it leaves flat land behind it on the slip of slope.
The flood plain will be covered the the river floods.
What is an meander migration?
On a meander, water travels at different speeds. Fast on the outside and slow on the inside.
Fast water erodes and slow water deposits.
These processes work together to move the meander. This is called meander migration.
What is an ox bow lake?
As a meander gets bigger, due to meander migration, a meander neck is formed. It is eroded on both sides and eventually the river breaks through and goes straight on.
The OBL is formed. After a while the OBL will dry out.
Describe interlocking spurs
A spur is a upper course feature.
In this part of the river, the load is big and angular. This means the river travels slowly and there is a lot of friction. The river uses up to 90% of its energy to overcome the friction.
When the river meets pieces if land sticking out, it goes around it and a spur is formed.
Describe how urbanisation impact rivers?
Building roads and drains means that water can reach the river quicker than rainfall.
This means the river is more likely to flood because there is too much water in the river channel.
Channelisation is put in place so the river bank is reinforced, the housing is protected and stops meander migration.
Building large ports for industry in a river can also be disrupted.
Poole Harbour in Dorset has to be dredged regularly as the river sediments and reduced deposition are dropped and block up the channel, meaning that large ships cannot get passed.
Describe how agriculture impact rivers?
When deforestation occurs it affect rivers as it interferes with the process interception (when the rainwater hits the trees leaves and takes time to reach the ground) and throughflow (when water flows through soil).
Fewer trees mean that the rainwater reached the ground faster, impacting erosion rates as the river will be more powerful.
Farmers use more chemical fertiliser, which impacts the ecology (plants and animals in the river), causing algae bloom and water channels to be clogged.
Farmers drain land close to rivers with artificial drainage ditches that allow water to flow to the rivers quickly, which can cause flooding as the natural river landscape is changed.
How does heavy rainfall cause flooding in a river?
The ground is saturated and the raincoat flows into the river quickly
