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Rivers: Upper, Middle and Lower Course

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Kathryn MacDonald

on 3 September 2013

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Transcript of Rivers: Upper, Middle and Lower Course

Learning Intention: To deepen our knowledge and understanding of the the formation process of a V-shaped Valley and Waterfall.
RECAP: Erosion and Transportation
THE UPPER COURSE
V-shaped Valley's
WATERFALLS
The Iguazu falls is located on the border of Brazil and Argentina.
HOW ARE WATERFALLS FORMED??
S3:Rivers
As we know the upper course the channel has little water in it. The channel is shallow enough to wade through and narrow enough to jump across.
There are differing bands of hard and soft rock in the upper course (like in the Grand Canyon) which can be eroded to form Waterfalls and gorges.
The river is using almost all its energy to move downstream, WHY?? What is in it's way?
Which band of the rock do you think will be eroded more quickly??
Think back to our study of the Grand Canyon...
In what direction was the the Valley eroding? WHY??
What processes of erosion were taking place?
A waterfall is a vertical flow of fast flowing water, often flowing from great heights.
Task- In Pairs, discuss and put the stages of a waterfalls formation into the order in which you think it occurs. Answer the questions (you can write on the sheet)
Look over your order. Are we still happy with our answers?
How are Waterfalls formed??
Were you correct..??
Stage 1: The River flows over a bedrock with bands of adjacent harder and softer rock.


Stage 3: The differential erosion creates a step in the landscape. The hard rock above is undercut erosion of the soft rock continues.



Stage 5: The broken pieces of rock in the plunge pool get swirled around by the river, abrading the channel further.
Stage 2: The hydraulic action of the river and the loose rock particles it contains, erode away the softer rock
Stage 4: The overhang of the hard rock can no longer be supported and collapses into a plunge pool formed in the channel bellow. The position of the waterfall moves back
upstream.
Stage 6: The gradient speeds up the river velocity. Erosion continues and the waterfall slowly eats its way upstream (headward erosion) leaving a gorge behind.
How are Waterfalls formed??
An effective way of remembering the different stages of a waterfalls formation is is by creating annotated diagrams.
http://www.bbc.co.uk/learningzone/clips/waterfalls-and-gorges-erosion-and-deposition/3239.html
Now watch:
V-shaped Valleys
Man WALKS over Niagara Falls...
Zambezi River Challenge
http://www.rednoseday.com/whats-going-on/challenges/hellandhighwater
What have we learned?
On your post-it note write...
Three facts you have learned today
Something you feel needs more work
In the last lesson we looked at How rivers move and WHY!
How is the rivers velocity affected?
EXTENSION TASK: In what instances can the processes of erosion taking place in a V-shaped Valley occur at a faster rate?
What percentage of energy do rivers use to overcome friction?
How is a Waterfall formed?
Task- Now using our diagrams we have created and the information from our 'How waterfalls are created and destroyed by rivers' worksheet...

Write an extended paragraph:
What is a Wetted perimeter?
Why is the river's velocity greater as it moves nearer to the sea?
What are the three key processes that are taken place in a river at any one time?
http://whs.moodledo.co.uk/mod/resource/view.php?id=51688
'Describe and explain the way in which a Waterfall is formed' (remember in add in the processes of erosion).
How would we start our paragraph??
TASK: In pairs, discuss AND match the pictures with the description process.

Put the formation of a V-shaped Valley into order (from beginning to end!). Glue them into your jotter.
How do they form??
Task: In pairs, work together to create 5 annotated diagrams of the differing stages of a waterfall. Use your worksheet to help you. Think about what happens in each stage... How do you think they should look?
Here is Stage 1 to get you started...
What have we learned today??
On our post-it note...
Write down three facts we have learned today.
Write down one thing we feel not as confident with.
What features can we find in the upper course?
At which point is the river fastest?
The Middle Course
The Middle Course
What features can we find in the middle course?
As we know, the middle course has much more water in it due to all the tributaries joining the main channel?
Meandering channels
Panoramic Views of Meanders in Utah
http://www.airpano.ru
Meanders
This video shows how meanders develop over time using a flume table and water which has been dyed red to make it easier to see where it flows.
BBC Class Clip 403
How are Meanders formed?
Task
The deeper the channel, the faster the flow. the faster it flows, the deeper it erodes. The shallower the channel, the slower the flow, the slower it flows, the more deposition takes place.
OX- BOW LAKE
Task: In pairs.. DISCUSS!
How do you think Meanders develop into Ox-Bow lakes?
Ox Bow lake
Meander
How are Ox-Bow lakes formed??
How are Ox-Bow Lakes formed??
As a river winds its way to the mouth, then the meanders can begin to curve tightly.
Rapid erosion is taking place on the outside of the meander, WHY??
River sediments are deposited on the inside of the meander, WHY??
Gradually the gaps between the two arms of the meander are narrowed and become very close. The river finally breaks through, (eg during a flood when the river has a higher volume and more energy). The loop is cut of from the main channel,the river becomes straighter and an Ox-bow lake is formed.
With the aid of annotated diagrams describe and explain how an Oxbow lake gets cut off from the river channel
When river cliffs collapse, the sediments become bedload in the channel, and the river can then transport these downstream before depositing them to form river beaches or point bars.
The river now has more energy, in which direction is it eroding to form meanders and river cliffs?
What begins to form at either side of the river channel?
How are they formed?
Task: Read Page 8 of your Textbook
Task: In pairs, discuss how you think meanders form.
How are Meanders formed?
Task
Read Page 8 of your Textbook
Complete the Meander Worksheet.
Colour in the areas of erosion, and deposits.
Complete Activity 3 to show what a meander channel looks like in a cross-section.

Describe the shape of the channel by imagining wadding through it (and then swimming)
Add labels using diagram C to help you.Identify where the maximum and minimum velocity is likely to be found.
The Lower Course
The Upper Course
The Lower Course
Meanders
How are they formed??
Due to the processes of Erosion and deposition. Meanders gradually migrate downstream.
Bends created by the force of the water (hydraulic action) and by abrasion (river load wearing away the river banks)
Inside of bend- River is slower, material is deposited creating a beach and rifles are found here. This creates more friction on the inner bend
Force of the water, erodes and undercuts the river bank on the outside of the bend where the water flow has more energy due to decreased friction and pools. This forms a steep river cliff.
By the lower course the bed and banks have been smoothed by the hydraulic action of the river water.
Why is the river faster flowing?
It has enough energy to transport large loads of fine sediment in suspension.
If there is a flood, where does the water spill over onto?
As the water drains back into the river channel the transported sediment gets left behind covering the floodplain in fine silt and sand
When the river reaches the sea it becomes an estuary (where freshwater joins the ocean) and deposits the remainder of its load creating sandbanks and mudflats. Saltmarsh may develop on the tidal mudflats.
How are Oxbow lakes formed?
Tasks
Learning Intention: To deepen our Knowledge and Understanding of the formation of Meanders and oxbow lakes.
The deeper the channel, the faster the flow. the faster it flows, the deeper it erodes. The shallower the channel, the slower the flow, the slower it flows, the more deposition takes place.
Do you remember what type of channel this is??
'With the aid of annotated diagrams, describe and explain the formation of a meander' (Use your worksheet and textbook to help you)
Answer
Formation of Floodplains
More on..levee's
http://whs.moodledo.co.uk/mod/resource/view.php?id=51679
Who uses the river and river valley's??
We know that the upper,middle and lower courses of a river have differing and distinctive features....
Task: Discuss- Who uses the river and the river Valley? What activities can you undertake?
Task: Using the 2009 Credit Map complete the land use and Maps Quiz.
Who uses the river and river Valley??
What happens as a river approaches its mouth??
Floodplain
Levees
Discuss: What are floodplains and levees and how do you think they are formed??
What features can we find in the lower course??
Floodplain & levees
The river's floodplain is the wide, flat area of land, on both sides of the channel. It is formed and shaped by both lateral erosion and deposition as meanders cut their way through the Valley.

Levees
Can you think of the US city whose levee failure during Hurricane Katrina resulted in 80% of it being flooded??
TASK
-Read pages 10-11 of your Textbook
- Complete the Floodplain and Levee worksheet in pairs, discussing your thoughts.

- River landforms Bingo!!
Who uses the River Dee and its valley??
Land uses down the Dee.. LOOK at the map for evidence
Food – farmland
Minerals – mines and quarries
Timber – forestry – coniferous, non-coniferous, mixed
Gamekeeping – moorland
Service provision – villages and towns
Routes – footpaths, tracks, cycle ways, roads, railways
Electricity generation and distribution – H.E.P., pylons
Communications – radio and telecommunications mast
Recreation – camp and caravan site, picnic site
Protecting the landscape – National Park, NT, FE, NNR
TASK
Using the cross-section cards... In groups discuss how the valley land uses of the river dee changes in differing courses. eg- More or less moorland?
What types of recreation are taking place as the river flows downstream?

- Can you make any links between the distance from the river, altitude of the land, aspect of the valley slopes with the landuse you discovered?
The river is carrying a large amount of suspended sediment. During period of flooding, the river will burst its banks and spill onto the floodplain. As the river over flows it is now in contact with more friction (think wetted perimeter!). What would happen to the rivers energy??
Sediment is deposited on the river bed, raising the channel. sediment (silt and sand) are also deposited on the floodplain creating a very fertile soil called alluvium. Do you think we use this area for farmland??
High natural embankments, situated on either side of the river channel. They are also formed as the river floods and overflows, losing energy and depositing sediment. The Heaviest materials are deposited first as they take the most energy to move. Over time they build up to be several meters high.
Discuss: If we control a river from flooding with levee's... will the eventual flood be more or less destructive?
Learning Intention: To deepen our knowledge and understanding of the formation of floodplains, levees and the the ways in which humans can use a river and its valley.
Braided channels at the mouth of rivers are known as deltas. As the river reaches its mouth, it slows down and it no longer has the energy to carry its sediment load. The river deposits the sediment faster than it can be removed.
DELTAS
There are three main types of deltas, named after the way they look..
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