Water On the Land

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  • Created by: Iman9123
  • Created on: 08-05-17 21:37
Why Do Rivers Change
due to the dominance of different river processes. How it changes depends on whether the erosion processes are dominant or deposition is dominant, which depends on the amount of energy the river has.
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The Upper Course
The river has plenty of energy as it is trying to reach its base level. It erodes downwards (vertical erosion) which produces a V Shaped Valley.
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Middle Course
river is closer to its base level so there is less vertical erosion. A lot of energy is used in transporting its load of eroded material and the river uses surplus energy to erode sideways (lateral erosion) which means the middle course is wide/flat
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Lower Course
the river is closer to its base and carries a heavy load of eroded material. If the river slows down, it deposits materials.
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A cross profile of a river
a diagram that shows the cross-section of the river channel and valley
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A long profile of a river
a diagram that shows how the gradient of the river changes as you move downstream
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Hydraulic Action
the force of the water on the bed and banks of the river erodes the river martial away. It is particularly powerful in a flood because the river is flowing very fast with a great deal of energy so the force of the water will be very strong
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Attrition
parts of the rivers load bumps, rubs against each other and wears each other down into smaller, more rounded pieces
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Abrasion
the load carried by the river rubs against the bed and banks, wearing it away
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Solution
some rocks and minerals are dissolved in river water and are carried in the water
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Transportation
The way in which the river carries eroded materials
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Traction
large boulders are rolled along the river bed due to the force of the water
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Saltation
smaller pebbles are bounced along the river bed. This is because the force of the water pick up the little pebbles and then drop them again as the flow of the river changes
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Suspension
fine sand and silt particles are carried along in the flow. This gives the river its brown colour
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Solution
minerals like limestone and chalk are dissolved in the water and are carried along in the flow
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Deposition
when the river loses energy (slows down) and drops some of its load
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A river may slow down enough to deposit material if
If they enter a much larger body of water that is not flowing, If the river has to carry extra load, If the river loses volume (less water in the channel), If the river hits an obstacle, If the river is slowed down by a bend in the rivers course.
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Waterfalls and Gorges-Step 1
Band of more resistant rock lies over less resistant rocks
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Waterfalls and Gorges-Step 2
Less resistant rock is eroded more quickly which leaves a step in the waterfall
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Waterfalls and Gorges-Step 3
More resistant ‘stronger’ rock is undercut, forming an overhang
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Waterfalls and Gorges-Step 4
When the overhang can no longer be suported, blocks of rock fall down
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Waterfalls and Gorges-Step 5
Waterfall retreats upstream
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Gorges
A gorge is formed over a very long period of time - the process of undercutting and collapsing is repeated continuously, and eventually a steep sided gorge is formed.
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Meanders
Meanders are bends in the rivers course. In the lower course, surplus energy is used up by swinging one way and the other which causes lateral erosion on the outside of the bends, and deposition on the insides.
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Ox Bow Lakes Step 1
There is particularly fast water flow on the outside bends of the river, resulting in lots of erosion here.
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Ox Bow Lakes Step 2
As a result, the outside bends move closer together as the meander neck becomes narrower.
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Ox Bow Lakes Step 3
This is a swan’s neck meander and as the process continues, the meanders move closer and closer together.
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Ox Bow Lakes Step 4
When there is a very high discharge, the river cuts across the neck and takes a straight course.
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Ox Bow Lakes Step 5
The role of subsequent deposition. The former meander is left as a horseshoe shaped ox- bow lake
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Levees
A levee is a natural embankment along the banks of a river.
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Levees-Step 1
As the river floods over its bank, the water loses energy and slows down
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Levees-Step 2
t cannot carry the biggest and heaviest silt particles, so drops them on the bank (forming floodplains*).
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Levees-Step3
Increased deposition on the river bed gradually raises the river bed upwards.
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Levees-Step4
After many floods, the material deposited on the bank build up and up, forming levees.
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Flood Plains
flat areas of land along a river. Lateral erosion makes the valley wider; the river deposits silt on the floodplain each time it floods.
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River flooding
normally when the volume of water discharge is so great that all the water cannot be contained within the river channel
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Other Reasons for flooding 1
Heavy rainfall causes infiltration so there is more water on the ground surface which cannot be contained within the rither
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Other Reasons for flooding 2
Rock type - if the rock is porous (permeable) then it will absorb the water, but if the rock is impermeable then it will not absorb any water
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Other Reasons for flooding 3
and use - in mainly residential or city areas, the land is often impermeable and flat therefore more likely to flood. In more rural areas with many trees, the trees will intercept and transpiration will occur.
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Other Reasons for flooding 4
Human factors can also include deforestation and building/construction
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Other Reasons for flooding 5
Relief height and shape of land
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Other Reasons for flooding 6
Previous weather conditions - if the ground is saturated or frozen, it cannot absorb much water leading to more surface run off
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How can we see how a river responds to a rainstorm?
by looking at a FLOOD HYDROGRAPH.
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Lag time
The difference in time between the peak of the rainstorm and the peak of the river discharge. The shorter the lag time and the steeper the rising limb, the greater the risk of flooding.
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peak flow’ or ‘peak discharge’
the highest discharge in the period of time shown
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What can River Discharge be affected by?
Length of rainfall, Strength of rainfall, Weather conditions
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Hard Engineering
involves building structures as a defence against flooding. This will often lower the effects or the likelihood of flooding.
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Hard Engineering Examples
Dams and Resevoirs, Changing the shape of the river, Straightening
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Soft Engineering
Involves letting nature take its course, adapting to floods and using natural processes to help deal with the heavy rainfall.
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Soft Engineering Examples
Flood Warning, Preparation, Flood Plain Zoning, Do nothing
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Ways of Managing UK Water Supply 1
Transfer water from areas of surplus to areas of deficit
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Ways of Managing UK Water Supply 2
Build more reservoirs and store more water
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Ways of Managing UK Water Supply 3
Fixing pipes so less water is lost during transfer
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Ways of Reducing the Demand for Water 1
People can reduce the amount of water they use at home
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Ways of Reducing the Demand for Water 2
Water companies want water meters installed that track exactly how much water is used and charge you accordingly so people are likely to be more careful with the amount of water they use
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Other cards in this set

Card 2

Front

The river has plenty of energy as it is trying to reach its base level. It erodes downwards (vertical erosion) which produces a V Shaped Valley.

Back

The Upper Course

Card 3

Front

river is closer to its base level so there is less vertical erosion. A lot of energy is used in transporting its load of eroded material and the river uses surplus energy to erode sideways (lateral erosion) which means the middle course is wide/flat

Back

Preview of the back of card 3

Card 4

Front

the river is closer to its base and carries a heavy load of eroded material. If the river slows down, it deposits materials.

Back

Preview of the back of card 4

Card 5

Front

a diagram that shows the cross-section of the river channel and valley

Back

Preview of the back of card 5
View more cards

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