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)
m³/ s
=
m/s
(depth and width)
x
m²
The main changes in the river channel are as follows:
•
•
•
•
Velocity (speed) =
Discharge =
Width and depth =
Load carried =
(e.g Increases / decreases downstream)
(Copy the table from Wider World p285- as you do this be thinking
‘Why do the following change as you move downstream?’)
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
explanation..
Friction ( a river looses 95% of its energy due to friction)
Which channel has most friction?
Lower Course
Course Channel
Channel
Lower
Upper Course
Channel
Wetted
perimeter
explanation..
Velocity (speed)
Which channel will have the fastest velocity?
Why?
Lower Course
Course Channel
Channel
Lower
Upper Course
Channel
explanation..
Energy and Power
Which channel has most power and spare
energy? Why?
Lower Course
Course Channel
Channel
Lower
Upper Course
Channel
explanation..
Erosion
The spare energy is used to erode deeper
and wider
Lower Course
Course Channel
Channel
Lower
Upper Course
Channel
Erosion
In your own words explain why a river changes as
you move down stream …
Copy
Upper Course
1. Small channel and lots of boulders in the river
(proportionally larger wetted perimeter!)
2.
3.
4.
5.
6.
Lots of friction
Slower speed or velocity
Little spare energy
Less erosion and load
Channel remains narrow and shallow and
discharge small
Copy
Lower Course
1. Volume of water increases because of
tributaries (less water in contact with the wetted perimeter
proportionally)
2.
3.
4.
5.
6.
Less friction
Higher velocity (faster)
More spare energy and power
More erosion and load
Channel becomes wider and deeper and
discharge increases
E
B
D
1.
2.
3.
A
4.
5.
C
What is A
What is B
Which would have
the higher velocity
D or C
Which place would
have the highest
discharge
Would A or B have
the largest load?
Why?