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How does a river change as you travel downstream
(The long Profile of a river)
A rivers long profile looks something like this:
Upper Course
Middle Course
Lower Course
Is it upper, middle or lower?
What are the differences between a river in its upper, lower , middle ?
Question? How does a river change as you travel downstream?
What changes can you think of?
Key river terms
1. Load = The amount of material being carried
by a river
2. Velocity = the speed of a river in metres per second m/s
Key river terms cont…
3. Discharge = is the amount of water passing a
given place at a given time
Discharge = velocity x cross sectional area ( speed) (depth and width)
m³/ s = m/s x m²
• Velocity (speed) = • Discharge = • Width and depth = (e.g Increases / decreases downstream)
• Load carried =
(Copy the table from Wider World p285- as you do this be thinking ‘Why do the following change as you move downstream?’)
The main changes in the river channel are as follows:
Why do rivers change from the upper to the lower
course?
Its all about energy ……..
Turn to page 282 in Waugh and read the 1st 2 paragraphs. Decide on the most important points
Friction ( a river looses 95% of its energy due to friction)
Which channel has most friction?
explanation..
Lower Course Channel
Upper Course Channel
Lower Course Channel
Wetted perimeter
Velocity (speed)
Which channel will have the fastest velocity? Why? Lower Course Channel
Upper Course Channel
Lower Course Channel
explanation..
Energy and Power
Which channel has most power and spare energy? Why? Lower Course Channel
Upper Course Channel
Lower Course Channel
explanation..
Erosion
The spare energy is used to erode deeper and wider Lower Course Channel
Upper Course Channel
Lower Course Channel
Erosion
explanation..
In your own words explain why a river changes as you move down stream …
Upper Course1. Small channel and lots of boulders in the river
(proportionally larger wetted perimeter!)
2. Lots of friction
3. Slower speed or velocity
4. Little spare energy
5. Less erosion and load
6. Channel remains narrow and shallow and discharge small
Copy
Lower Course1. Volume of water increases because of
tributaries (less water in contact with the wetted perimeter proportionally)
2. Less friction3. Higher velocity (faster)4. More spare energy and power 5. More erosion and load6. Channel becomes wider and deeper and
discharge increases
Copy
1. What is A
2. What is B
3. Which would have the higher velocity D or C
4. Which place would have the highest discharge
5. Would A or B have the largest load? Why?
A
EDB
C
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