Transcript Rivers and their Valleys

Sanctions
• Verbal Warning (1st)
• Second warning get moved seat (demerit)
• Removed from class for the lesson
• Referred to PT (Possible removal from
class for a longer period of time)
Rivers and their Valleys
Take a page in your jotter and copy the
mind map below.
Rivers
In pairs write down as many ideas that you already have
about rivers and their valleys.
The water cycle
Rivers in the landscape
Read 11A, page 86 in your textbook
Watershed
Confluence point – where
tributary meets main river
Tributary
Main river
Catchment Area
Using 11A, page 86 in your textbook
 Copy the following paragraph and fill in the blanks
A River shapes the physical landscape through
_________ processes.
These are:
_____________ - It removes soil and rocks.
_____________ - It carries them to a different
destination.
_____________ - It then drops the soil and rocks.
Erosion
Transportation
 Describe what the following words mean:
1. Source
2. Catchment area
3. Tributary
4. Mouth
Deposition
Key Terms
Source: where a river starts
Key Terms
Catchment area:
all the rain that
falls in the surrounding area flows into
the river
Key Terms
Tributary: streams that flow into
the main river
Key Terms
Mouth: where the river meets the
sea (it ends)
The Three Stages of a River
Erosion and
Deposition
Link to
Activeboard
For drop and
drag
Word Bank
Flat land
Gentle slope
Deposition
Steep slope
Tributary
Erosion
Mouth of river
Source
Label the diagram in your diagrams booklet
Use the following slides to fill in this table in your diagrams booklet
Upper Course
- the river is very narrow and shallow;
- valley is V-shaped;
- slopes are steep but with lots of obstacles the velocity is slow ;
- volume is not great (there is not a lot of water in the river);
- it does not carry much load - large to small rocks;
- most of its energy is used for erosion;
-most landforms have been formed by erosion
(e.g. waterfalls).
Fill in the column 'Upper Course' in your table using the above information
Middle Course
- the river is quite wide and deep;
- the valley floor is quite wide;
-slopes are gentle but the river speeds up as there are
less obstacles;
- the river has a large load - sub-rounded rocks;
- energy levels in the river are medium;
- the river erodes and deposits material;
- landforms are due to a combination of erosion and deposition
(e.g. river cliffs and river beaches).
Fill in the column 'Middle Course' in your table using the above information
Lower Course
- the river is wide, deep and quite fast as there are no obstacles;
- the valley floor is called a floodplain (it is wide and flat);
- most of the rivers energy is used to carry its large load which
is mainly fine silt and mud so there is little erosion;
- most landforms have been formed by deposition (e.g. levees
and floodplains);
- some erosion takes place in times of flood, forming features
such as ox-bow lakes.
Fill in the column 'Lower Course' in your table using the above information
River Processes –
Erosion and Transportation
Rivers can deepen and widen their valleys by:
Corrasion – rivers use the stones and pebbles they
C carry (its load) to smash against the sides and bottom
of the river.
Attrition - the stones and pebbles the river carries
(its
load)
rub
against
each
other.
A
Over time the size of this load becomes smaller and
more rounded.
S Solution - this is when rivers dissolve material
Hydraulic Action - the sheer force of the water
H causes the outer banks of the river to break up and
collapse. It is most effective in times of flood.
Erosion
• Erosion which causes the river to deepen is called
vertical erosion - commonly found in the upper course.
• Erosion which causes a river to widen is called
lateral erosion – this is more common in the middle
and lower courses of a river.
Describe, in your own words, the two different types of erosion
Transportation
Rivers transport their load by:
Solution – some material may be dissolved
by the river.
Suspension – very small particles can be
carried along in the river. The faster
the river = the more it can carry
Saltation – larger particles bounce along
the river bed. These particles can cause
other larger particles to become dislodged
Traction – the largest boulders (particles) roll
along the river bed at times of flood
when the energy level in the river is high.
Fill in the missing words in your diagrams booklet
River Landforms –
Upper Course
Upper
Course
After studying the upper course we will understand how the
following features were formed:
•
Source – the point at which the river starts.
•
Interlocking Spurs – where the river winds between ridges.
•
Gorge – deep valley caused by wearing back of a waterfall.
•
Waterfall – often where the river crosses a band of harder rock.
•
V–shaped valley – produced in upper course where the river
erodes downwards.
V-Shaped Valleys and Interlocking Spurs
Read 11E, page 88
Fill in the V-shaped valley diagram in your diagrams booklet
Freeze-thaw or frost shattering:
1. At night when temperatures freeze the ground expands
and water in the cracks in rocks also expands.
2. This process of freezing loosens rocks.
3. These rocks fall down the hill by gravity.
4. They enter the river and are used down stream for
corrasion.
5. This process makes the interlocking spurs steeper.
V shaped valley formation
Q. Using the two photos above explain how a v-shaped
valley is formed (4 marks)
Don’t forget to mention interlocking spurs!
Try to include these key words:
Upper course Vertical
Hydraulic Action
Freeze Thaw Interlocking Spurs
Corrasion
Model Answer
1.
In the upper course of the river the steep sides of the
valley provide energy for the river to cut downwards
through corrasion, hydraulic action and solution. These
are mainly vertical erosion in the upper course.
2. Rocks on the sides of the valley are broken up by freeze
thaw (weathered) and slip down the slope into the river.
3. Gravity then transports material away by the river, even
more at times of flood.
4. The river is forced to swing from side to side around
interlocking spurs.
Watch the video clips on the Upper Course of the River
Tees and Upland River Tees and answer the questions in
your diagrams booklet
1. Upper course video questions
2. Upland river Tees video questions
Important date:
Wednesday
th
17
June
*Finished Source Sheet*
Waterfall
Formation
Read 11F, page 88 in the textbook
Copy down figure 11.5, page 88 into
your jotters
Note down the 4 bullet points from 11F, page 88
Copy and label the diagram in your booklet
Watch the video clip on High Force waterfall on the river
Tees and answer the questions in your diagrams booklet
River Tees waterfall video questions
Exam Style Question
• Using diagram(s) describe, in detail, the
formation of a waterfall
(4)
Model Answer
• The river flows over bands of
softer and harder rocks
• Softer rock is more quickly
eroded (through Hydraulic
action)
• The river undercuts the harder
rock leaving an overhang
• The river forms a plunge pool
below the waterfall
• Overhanging rock is unsupported
and falls into the plunge pool
• The waterfall is moved upstream
• This process continues and a
gorge is cut back into the
hillside
1
2
3
4
5
Source
Interlocking Spurs
Waterfall
Gorge
V-shaped valley
River Landforms -
Middle Course
Middle
Course
After studying the middle course we will understand how the following
features are formed:
6) Meander – the river erodes from side to side.
7) River cliff – the river moves faster on the outside of the bend and cuts
into the valley side. The erosion undercuts the ground, leaving a river
cliff
8) River beach (slip-off slope) – the river moves more slowly on the inside
of the bend. It cannot carry the larger pebbles and these are dropped
here.
Middle Course - Meanders
Read 11H, page 89
Summarise the passage in your own
words
Meander = a bend in a river
River bend - meander
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
Cross section of a meander bend.
Sketch the diagram in your booklet and mark on the
following:
area of deposition
Meander bend on the River Conwy
A
B
Explain why there is more deposition at ‘A’ rather than at
‘B’, using a diagram.
(4 marks)
Watch the video clip on the Middle Course of the River
Tees and answer the questions in your diagrams booklet
Link to channel 4 video
River Landforms –
Lower Course
Lower
Course
After studying the lower course we will understand how the
following features form:
9) Flood Plain – a plain, bordering a river, which has been formed from
deposits of sediment carried down by the river.
10) Ox-bow lake – a separated meander which leaves a u-shaped lake.
11) Levee – high ridges of silt deposits at the side of the river.
12) Estuary – the open mouth of a river, where it meets the sea.
Lower Course
Read 11M, page 89 in your textbook
Complete the sentences below:
• In its lower course the river is ______________,
___________ and has more __________.
• The wide, flat valley floor is called a __________ __________.
• The river carries a ____________ load.
• It ________________ its load in some areas because
it doesn’t have enough _______________.
• Most of the landforms in the lower course are produced by
__________________________.
Floodplains
Floodplains
Floodplain formation
• Floodplains and levees are formed by deposition in times of
river flood.
• When a river floods it deposits the heaviest of these particles
first.
• The larger particles, often pebble-sized, form the leveés.
• The sands, silts and clays are similarly sorted with the sands
being deposited next, then the silts and finally the lightest clays.
• This deposition makes up the floodplain.
Cross section of a floodplain.
Draw a simple sketch of the diagram and annotate with
the following labels in your booklet:
leveés
sands
clays and silts
In your jotter explain how a floodplain is formed
The formation of Oxbow lakes
Oxbow lakes
Draw the following four diagrams in the correct order of oxbow
lake formation. Match 3 of the diagrams with the most
appropriate explanation from ‘A’, ‘B’ and ‘C’.
1.
2.
XX
3.
XX
4.
X
X=
erosion
on the
outside
of the
meander
bend
A. The river meanders. The fastest flow is therefore on the outside
of the bend. This fast current erodes the meander neck.
C. The meander neck is further eroded until only a thin piece of land
separates the two channels.
B. The river floods and erodes through the thin meander neck. The
river now takes the easier, straight course. The meander loop is
left as an oxbow lake.
Narrow meander neck
Future oxbow
Lake formation
Now complete core questions 6 and 7 on page 91 of
textbook.
Watch the video clip on River Tees Meanders and River
Tees Lower Course and answer the questions in your
diagrams booklet
Link to channel 4 meanders
Link to channel 4 lower course
Steep valley sides are
difficult to farm
and build on.
A narrow river is easy
to dam to make a
Reservoir.
Fast flowing water can
be used for generating
hydro-electric power.
Fast-flowing “white water”
is suitable for canoeing
and other water sports
The water is usually too
shallow for ships to use
Waterfalls prevent ships from
using the river.
Waterfalls and steep slopes
attract sightseers.
Farmers can grow crops
on the flat land
The flat valley floor
is a useful route for
roads and railways.
The river is usually too
shallow for ships to use
The flat land is suitable
for caravan sites and
picnic sites.
There is a small area
of flat land suitable
for building.
The land is easily
flooded; levees
are sometimes built to
prevent this.
Deep water is suitable
for ships and the river
can be dredged to make
it even deeper.
The flat valley floor provides
suitable land for farming and
building on.
Meanders are difficult
for ships to navigate but
they can be straightened
You must design a land use poster which explains
what each course of the river is used for.
Use the following information from the textbook:
11G page 88
11L page 89
11P page 90
The poster must be done in your jotter and will be
finished off for homework if not completed during the
lesson
Hill sheep
farming
Forestry on
Steeper
slopes
River
provides
transport
Hydro-electric
power
Reservoir for
water supply
Rivers Landuse
Poster Example
Skiing, climbing,
hillwalking
Wildlife and
nature trails
Settlements
on lower,
flatter land
Sewage
dumped in river
Arable and
Pastoral
farming
Sheltered
Floodplain
easy to build harbour
Match the label to the correct letter
c
Catchment area
Confluence
b
d
Tributary
Source
a
Learning Intention – develop map skills to identify river map features
tributaries
V shaped valley
Steep
Valley
sides
meander
ox-bow
lake
Flood
plain
Rivers on Maps
In an exam you might be asked to describe the physical
features of a river and its valley.
• Read 11D on page 87 of your
textbook.
• Copy the table below
River
Valley











Direction
Features
Tributaries
Slope
Straightness
Direction
Width
Floodplain
Features
Slope
Straightness
In Pairs:
The Rivers Dee and Allt an t-Slugin and their valleys are very different.
• Pair A will describe the river and valley of the River Dee
Describe these differences in detail.
4 marks
•Pair B will describe the river and valley of Allt an t Slugain
• You have 10 minutes to do this.
•You will then combine both your answers to form a complete
answer which describes the difference between the two river
valleys in detail.
REMEMBER when describing the river and its
valley you must mention:
* the width of the river
* any features in the river valley
•the slope of the river
*the width of the valley floor
*the direction of flow of the river
* the slope of the valley sides
When completing your final answer, use comparing words such
as WIDER, STEEPER
The Rivers Dee and Allt an t-Slugain and their valleys are very
different.
Describe these differences in detail.
4 marks
• The River Dee is much wider than the Allt being
over 50 metres wide.
• The floor of the River Dee is wide and flat,
whereas the Allt is a more V-shaped valley.
• A large area of the floodplain of the River Dee is
marshy land.
• The Allt has a steeper gradient than the Dee, so
probably flows faster.
• The Dee flows east, while the Allt flows south
east.
• The Dee has steep slopes only on the south
side of the valley but the land on both sides of
the Allt are very steep.
There is a plan to construct a dam and power station in grid square
8853. Using map evidence, describe the advantages AND
disadvantages of building such a scheme at this site.
6 marks
There is a plan to construct a similar dam and power station in grid
square 8853. Using map evidence, describe the advantages AND
disadvantages of building such a scheme at this site.
6 marks
Advantages
Disadvantages
• Dam hanging valley to provide
deep reservoir
• Many streams to provide
water
• Large numbers of streams
suggest impermeable rocks,
needed for reservoir
• Big difference in height
• Easy access for construction
traffic
• Used water can be discharged
into sea
• Disturbance to people at
Annat
• Loch Hotel may have to be
demolished
• People will lose sense of
community if hotel is lost
• Woodland and scenery will be
lost
• River bed will be altered
• The appearance of the
waterfall will be ruined
1. In which general direction is the river Spey flowing?
STANDARD
GRADE
RIVERS
MAPPING
EXERCISE.
2. Give
the six figure
reference
where
the River
Calder joins the
River
UsingSpey.
the 2005 General map extract- Kingussie- answer
3. What
is the junction
of two
rivers called?
the following
questions
as accurately
as possible.
4. What do you call a small river flowing into a larger river?
5. Name -and briefly describe- any physical river features that
have formed along the stretch of the Spey shown on the extract.
6.Choose one feature, and with the aid of a well-labelled diagram,
explain how it is formed. Pay particular attention to the two main
processes that rivers perform.
7.Calculate the maximum and minimum widths of the flood plain of
the river Spey. How did you do it?
8.Describe the gradient of the river bed along this stretch. How
fast do you think it is flowing?
9. What two pieces of evidence are there that the river Spey can
be a flood danger?
10. What recreational activities take place on or next to the flood
plain?