Rivers and Waterfalls Flashcards
Water is constantly moving from the _______________ to the earth and back again. This is called the _____ _____.
Atmosphere
Water cycle
Most water reaches the earths surface as ____ where it either _____ as rivers, or soaks into the ____.
Rain
Flows
Soil
Water passes into the air by a process called ______________ which turns liquid water into vapour.
Evaporation
Condensation then occurs as the air cools and ______ are formed.
Clouds
Surface runoff:
Here water moves directly over the surface in eg. a river.
Infiltration:
This is the process where water is soaked into the soil.
Throughflow:
This is the process where water flows through the soil towards eg. a river.
Percolation:
This is a process where water moves into underlying rock.
Groundwater flow:
This is the process where water flows through rock towards eg. a river.
Interception:
This is when roots from plants and trees suck up water from the soil as part of their growth. They intercept water.
Source-
Start of a river
Mouth-
Where a river joins the sea
Meander-
Sweeping bend in a river
Tributary-
Small stream that joins a larger river
Confluence-
The point where two rivers join
Drainage basin-
Area drained by a river system
Water shed-
A raised area of land separating one drainage basin from another
What are the three parts of a river?
Upper course
Middle course
Lower course
Erosion:
This is the wearing away of the land
Hydraulic action:
This process involves the force of water against the bed and banks
Abrasion/Corrasion:
This is the process by which the bed and banks are down by their rivers load. The river throws three particles against the bed and banks, sometimes at high velocity.
Attrition:
Material carried by the river bump into each other and so are smoothed and broken down into smaller particles.
Corrosion:
This is the chemical action of water. The acids in the water slowly dissolve the bed and banks.
What is ‘discharge’?
The amount of water in a river at a particular point.
How do v-shaped valleys occur?
A rivers discharge is low in the upper course of the river only has enough energy to erode downwards. This is called vertical erosion. The valley sides are slowly broken down through weathering. The weathered material is transported via gravity and rainfall towards the water channel. This process steepens the valley. The steep sided and narrow valley shape that is created is typical of upland rivers.
What are interlocking Spurs?
In the upper course of a river the river does not have much energy to erode. When the river meets and area of hard rock it winds around it. A serious of hills form called Spurs.
What are the first two points about waterfall formation?
1) the river meets a layer of less resistant rock.
2) the underlying rock is eroded more quickly by eg. abrasion
What are the third and fourth points on waterfall formation?
3) this causes undercutting
4) the more resistant rock is left unsupported
What are the last two points on waterfall formation?
5) it collapses and helps to form a deep plunge pool.
6) this process is repeated and the waterfall retreats upstream to form a gorge.
What two things are still important processes in landforms in the upper course of a river?
Erosion and deposition.
What are the six stages of the water cycle?
1) Precipitation 2) Surface water 3) Ground water
4) Transpiration 5) Evaporation 6) Cobdensation
What is lateral erosion?
Erosion going side to side.
The first two points on landforms in the middle course of a river:
1) traction- Boulder and pebbles are rolled along the river bed.
2) sactation- sand sized particles are bounced along the river bed by the flow of water.
Last two points on landforms in the middle course of the river:
3) suspension- fine clay and sand particles are carried along within the river
4) solution- some materials dissolve in the water
Meanders are…
A bend in a river.
First two points on a cross section through a meander:
1) in the middle course rivers erode laterally
2) water is pushed to the outer bend of the meander
Last two points on a cross section through a meander:
3) the river erodes the outer bend to form a river cliff eg. abrasion and hydraulic action
4) the water moves to the inner bend of the meander. It deposits material. This is called a slip off slope.
First point on oxbow lakes:
The outer banks of two meanders are both eroded and get closer together.
Second point on oxbow lakes:
When the river floods it breaks through the thin meander as the river wants to take the easiest and fastest route.
Third point on oxbow lakes:
The river now has a new course and an oxbow lake is formed. It can become inhabited by vegetation.
A flood plain is found in the…
Lower course of a river. It is the result of deposition.
How is a flood plain formed?
It’s formed by deposition in times of river flood.
When a river floods it deposits the __________ material it’s holding first. These are often larger particles eg. ______ sized and form ______. Every time the river floods ___________ build up the _____ _____.
Heaviest Pebble Leveés Deposition Flood plain
Why are flood plains very good for farming?
Because the soil is very fertile.
How do floods occur?
A flood occurs when there is too much for a river channel to hold. The excess water simply spills over the rivers banks and floods the neighbouring land.
What is the most common reason for a flood in the uk?
Heavy rain or in the spring, rain and melting snow combined.
Material that is transported by a river is called its ____.
Load
What is a flash flood?
A flood that occurs quickly without warning.
Campsite flood: When?
August 1996
Campsite flood: Where?
The Pyrenees campsite in northern Spain
Campsite flood: What?
A flash flood sent torrents of water, mud, rocks and uprooted trees through a campsite.
Campsite flood: Who?
Over 60 people were killed and 200 injured.
Campsite flood: Why?
The floods followed two days of heavy rain and thunderstorms. A bridge above the campsite became blocked by broken tree stumps during the storms. Water collected behind the bridge and eventually the bridge gave way. All the water that had built up behind the bridge poured through the campsite.
Flood use:
When a river floods the surrounding area, the material it is carrying gets deposited this material is called alluvium that forms the flood plain. It is very fertile and therefore attractive to farmers.
How can trees help prevent flooding?
Planting trees in the river helps because the trees act as a break on the rainfall and reduce the amount of rain reaching the ground. Trees also use up water as they grow.
River channels are made…
Larger by dredging so that they can hold more water.
Walls called flood…
Embankments are built to increase the height of the river channel.
Flood relief channels…
Can be built around towns. They divert excess water out of rivers and reduce the risk of flooding.
