Transcript River Studies 3: The 3 courses of a river

River Studies 3:
The 3 courses of a river
The 3 courses of a river.
 Rivers have 3 main course:
Lesson aims:
 The
upper
Over
thecourse
next few lessons
we
will
learn
about the different

The
middle
course
courses of the river.
 The lower course
Source
of river
Upper
Course
Middle
Course
Lower
Course
V-Shaped valley
with steep sides
Large load
(eg big rocks)
Fast flowing
water
Lots of
vertical erosion
The upper course of the river
Task:
Look at the picture that comes
up and write down everything
Lots of “energy”
Interlocking
in the water
Spurs
you can see in it.
Think about the shape, the
Shallow water
speed and
the load.
A typical
upper course
valley with
, steep
valley sides
and active
slope
processes
Characteristics
Upper Course
Depth
Width
Shallow
narrow
Speed
Fast
Middle Course
Lower Course
Straightness winding
Load What do you think the land here could
be used for by people?
large
Type of load
angular
Features
Land Use
V-Shaped Valleys, Interlocking Spurs,
Waterfalls
Land Use in the Upper course
 Gorge-walking
 Hill sheep farming
 Hydro-electric power (HEP) reservoirs
 Rock Climbing
 (No crop farming as the land is too steep, not
many roads and communication links)
Formation of a V-Shaped Valley
This is VERY IMPORTANT as it comes up
all the time!
When doing this you must:
Draw at least 3 diagrams
Label the diagrams
Have some text explaining what is
happening
Terms you need to know
Vertical erosion
Hydraulic action
Freeze thaw action (Weathering)
Mass movement
Freeze Thaw
When water gets into cracks in
rocks and then freezes.
This causes it to expand and then
break the rocks apart.
Mass-movement.
This is when gravity pulls
material down slopes.
It causes rocks to fall into the
river.
Task part 1 Diagrams
 You are going to be given a textbook answer to
the formation of a V-shaped valley.
 You must come up with the 3 diagrams that will
help you to explain what is going on.
 To do this collect a mini white board.
 2 minutes to read through the text.
 5 minutes to come up with 3 diagrams.
Quick test
 The force of the water weakens and
1. HYDRAULIC
breaks
up the rocks.ACTION
2.inSOLUTION
 The water
the river dissolves the
minerals3.
inATTRITION
the rocks
 As the pebbles carried by the river crash into
4. they
ABRASION
each other,
become smaller and rounder
 The material carried in the river wears
away the river bed
Suspension
Traction
Solution
Saltation
Diagrams
1
2
3
Task part 2 labels
 Now you have the diagrams and the text
 The next thing you need is detailed labels.
 Using the paper you have been given in two’s
write on all of the labels you can think of.
Labels for a V-shaped valley.
Valley start of with
slightly sloped
sides.
The fast flowing
river begins to
erode the valley
Processes such as
abrasion/corrasion
take place
Mass movement
begins to weaken
the material at the
sides of the valley.
Vertical erosion
takes place
eroding the valley
downward.
Weathering (freeze
thaw) weakens the
valley sides.
Hydraulic action
takes place
wearing down the
rock.
Eventually the
material is
weakened so
much it falls into
the river
The fast flowing
river transports
much of the
material
A V-shaped valley
is left with steep
sides
You also have to write some text
The example you have in your jotter is a
good one but it could be simplified.
Read over it and try and turn it into 4
sentences.
Interlocking spurs are formed when
the relief of the land changes
and therefore the river
changes direction
Formation of interlocking spurs:
Interlocking spurs are formed exactly the same as
a V-shaped valley. (so you would start
with the same diagrams
andalso
text.)
This may
occur if
the river hits a large rock
or area of hard rock it can’t erode.
Next Feature.
Waterfalls
Waterfall
1) Water flows over hard rock and then
onto soft rock
2) Over time the soft rock is eroded
3) A waterfall is created
Watch waterfall video
Formation of a waterfall
Waterfall
Retreats upstream
Hard rock
Soft rock
Undercutting
The
overhang
The
erodesprocess
the
Eventually
Vertical
erosion
startsrock
again
softer
collapses
Forms plunge
pool
forming
an overhang
Steep sides
( gorge )
Eroded rock
Waterfall Formation
 Water flows over areas of hard rock and
onto soft rock
 Eroding the soft rock more quickly.
 Over time the hard rock sticks out over the
soft rock.
River Landscapes
Standard Grade
•The soft rock underneath is eroded
further by the force of the water
(hydraulic erosion).
•This area is called the plunge pool.
River Landscapes
Standard Grade
•In time the hard rock above the plunge
pool collapses falling into the plunge pool
•The pieces of hard rock help to erode
the plunge pool further (corrasion) and
are themselves eroded by attrition.
•The waterfall continues to move
upstream over
time forming a gorge.
UPSTREAM . .
WATERFALL
RETREATS . .
OVERHANG
UNDERCUT
SOFT ROCK
PLUNGE
POOL
Waterfall video again
Middle course of a river.
Key features:
Everything is medium:
 The width is medium
 The depth is medium
 The speed is medium
What
doisyou
land
The type
of load
smallthink
and medium
rounded
. (nobe
bigthis
rocks)
userocks
could
time?
Land is quite flat. Although you may get slight
hills at edges.
It has meanders (bends in the river)
Land use
Settlement - towns built on flat land near river
bridging point. Routes along the valley often meet at
bridges.
Farming - on flat valley floor where soils and
weather are better.
Tourism - farmers provide simple accommodation
(B&B, caravan, camping) to supplement their income.
Middle course location provides tourists with access
to both uplands and lowlands.
Fishing - good source of income for landowners,
especially in salmon rivers.
Formation of a meander.
 Important points.
 Erosion occurs on the OUTSIDE of bends.
 Deposition occurs on the INSIDE of bends.
Lesson starter:
Take the title Formation of a meander.
Take half a page in your jotter and draw a river along it.
Then swap it with the person next to you and they have to
draw on the areas of erosion and deposition.
Formation of a meander.
It’s the same as all other features:
Diagrams
Labels
Text
I am going to give you the text.
Your task it to draw the diagrams.
Collect a whiteboard and pen.
For each of the statements you see
you must draw one picture.
Diagram sheet
 1) As a river moves down stream is does not flow
straight, it curves slightly. This is because it will
follow the easiest route and due to it flowing faster
in some paces than others.
 2) The river flows faster on the outside of these
curves and slower on the inside.
 2) Due to this we get erosion on the outside of the
curves and deposition on the inside of them.
 3) Over time this erosion and deposition causes the
river to bend.
Diagram sheet
 4) The erosion continues and the curve becomes
bigger. The ares of erosion and deposition become
bigger too.
 5) Eventually large meanders are left in the river.
They continue to grow as the erosion and
deposition get greater.
River bend
Fastest current
slowest current
Bank will
collapse
Small
river
cliff
Outer bank
Is undercut
Deepest part
of the river
Slip off slope
( river beach )
Deposition of
Sand and shingle
Quick quiz: part 1
Erosion
Or
Transportation
Get a whiteboard and pen.
On one side write erosion.
On the other side write
transportation.
Corrasion
Corrasion – rivers use the stones and pebbles they
carry (its load) to smash against the sides and
bottomof the river.
Hydraulic
action
Hydraulic Action - the sheer force of the water
causes the outer banks of the river to break up and
collapse. It is most effective in times of flood.
Traction
Traction – the largest boulders roll
along the river bed at times of flood
when the energy level in the river is high.
Attrition
Attrition - the stones and pebbles the river carries
(its load) rub against each other.
Over time the size of this load becomes smaller and
more rounded.
Saltation
Saltation – larger particles bounce along the river
bed. These particles can cause other larger particles
to become dislodged
Quick quiz part 2
You are going to see a
statement.
You must draw a picture that
goes along with it.
V-shaped valley
1. The valley starts of with gently
sloping sides.
2. Fast flowing water begins to erode
the valley vertically.
3. Processes such as abrasion take
place as the rocks in the river are
transported.
V-shaped valley
1. Hydraulic action makes the valley
deeper.
2. Mass movement and freeze thaw
action make the sides of the valley
weak.
3. Vertical erosion takes place.
Waterfall
1. Water flows over hard rock then
onto soft rock. The soft rock is
eroded more quickly.
2. Overtime an overhand and plunge
pool are formed.
Waterfall
1. The rocks in the plunge pool as well
as vertical erosion cause the soft
rock to erode backwards.
2. The overhang becomes too heavy
and eventually falls.
Homework: Tuesday 27/03/2012
Explain the formation of a v-shaped
valley and a waterfall. You may use
diagrams to in your answer.
8 KU
Lesson starter.
With the person beside you each
take a number 1 or 2.
Number 2: What are the
Number 1:
2: Explain how a
characteristics
of
the
rivers
You
will
take turns
the
v-shaped
meander
Waterfall
valley
isexplaining
formed.
is formed.
featuresmiddle
of a river course?
of river course to
ach other.
The lower course of a river
 You are going to see a picture of the lower
course of a river. Using this and your new
knowledge of rivers you must write down what
you think the characteristics of the river will be.
Include:







Its width
Depth
Speed
Load (amount and type)
The land around it.
Features
Land use
•
•
•
•
•
•
•
Width
Depth
Speed
Load (amount and type)
The land around it.
Features
Land use
 Lower Course of the river features:
 Its width:
 Very wide
 Depth
 Very deep
 Speed
 Slow
 Load (amount and type)
 Large load (lots of it), but small rocks, sands ad silt.
 The land around it.
 Large flat flood plain
 Features
 Ox-bow lake.
 Delta
 Mouth of river.
Land use
Large settlements.
Transport routes.
Industry.
Ports for trade.
• Mystery feature:
• How were these
features formed
on the
landscape?
The formation of an Ox-bow lake.
 Occasions