1. Ok 1 (U) notice anything?
Oh no Jackie
Its those
First Years
again!

2. First year geography Ms Clifford
Rivers: How they shape our land

3. Some important river terms
Source-where a river begins
Course- the route it takes as it flows from an upland area down through its valley until it enters the sea
Tributary- a stream or river which joins a larger river
Confluence- the point at which a tributary joins the river
Mouth- the place where a river enters the sea
Estuary- the part of the mouth that is tidal
River basin- the area that is drained by a river or its tributaries
Watershed- the high ground that separates one river basin from another

4. There are 3 stages in a rivers life
The youthful stage (upper stage)
The mature stage (middle stage)
The old stage (lower stage)

5. 3 stages of a rivers life…just like humans life!

6. The Work of Rivers
The erosional work of streams/rivers carves and shapes the landscape through which they flow.
3 functions of rivers
Erosion=wearing away the landscape
Transportation=moving the material away (called the rivers load)
Deposition=to drop the load along the way

7. The Work of Rivers 1. Hydraulic action The force of the flow of the
RIVERS MAY ERODE IN 4 WAYS:
Hydraulic action
The force of the flow of the
moving water erodes pieces of rock
from the banks and bed of the river:
this is called Hydraulic Action
(This material is called the load)

8. The Work of Rivers 2. Abrasion
Load carried by a river will scrape against the soil and rock along the bed and banks of the river, deepening and
widening the river channel. This process slowly wears the bed and banks away.

9. The Work of Rivers 3. Attrition When rocks carried by the river rub
against each other they are worn down
and smoothed.

10. Attrition

11. The Work of Rivers 4. Solution
Certain minerals in rocks like limestone can be dissolved by the river

12. The rate of erosion depends on
The size of the river- it erodes faster when it is in flood
The speed of the river- a fast flowing river has more erosive powers
The hardness of the rock- some rocks erode more easily than others

13. How does the river transport its load?
It does this in 4 different ways:
Traction-rolling of stones
Saltation- bouncing of stones
Suspension- carrying of stones
Solution- the load is dissolved

14. 4 ways it transports its load

15. Deposition of a river
This is the dropping of the rivers load

16. The Work of Rivers Rivers will deposit their load when:
They lose speed
There is a reduction in water in the rivers channel
They flow into a lake or sea
The slope or gradient of the river is reduced

17. The Work of Rivers A river’s volume decreases when Dry season
Dry region with high evaporation
Presence of permeable rocks
Receding flood waters

18. The Work of Rivers A river’s speed decreases when It enters a lake
It enters a calm sea
It enters a gently sloping plain

19. 3 stages of a river
Youthful stage
Mature stage
Old stage

20. The youthful stage of a river
At this early stage of the river, it flows down a steep gradient.
The river has a small volume
It cuts down into the rock by a process known as vertical erosion
It does this though hydraulic action, abrasion, attrition or solution

21. Features /landforms of the youthful stage
V shaped valley
Interlocking spurs
Potholes
Waterfall

22. Yummy 

23. V Shaped Valley

24. V Shaped Valley
V shaped valley have steep sides and narrow floors. These are formed as the river cuts down into its bed, deepening it by “vertical erosion”. Meanwhile weathering breaks up the soil and rock, weakening the sides of the valley. They eventually collapse and the debris falls into the river. This gives it the v shape

25. Interlocking spurs

26. Interlocking spurs
These are the areas of high ground that jut out like a jig saw from each side of the valley. If the river meets obstacles of hard or resistant rock like granite-it is unable to cut through it. Instead it flows around them but still continues to erode downwards. This is why the river develops a zig-zag course

27. Potholes
Potholes are circular-shaped hollows found on the riverbed. When the riverbed is uneven, the water begins to swirl around. Pebbles that are carried by the swirling water cut down into the riverbed, creating hollows called potholes. This is the process of abrasion. Example: Liffey

28. Waterfalls

29. Waterfalls
A waterfall is a feature where the water flows or falls over a vertical slope.
It develops where a band of hard or resistant rock lies on top of a band of soft rock. The softer rock is eroded by the river more quickly than the hard rock. This causes a plunge pool to be formed by the force of the falling water.
The falling water also cuts under the waterfall to form an over-hang, which eventually collapses.
As this process repeats itself-the river gradually retreats upstream
Examples-Powerscourt, Glencar waterfall or Torc waterfall

30. The mature stage of a river
The river has a greater volume since many tributaries have joined it. It flows over a gentler gradient.
It has a larger load of material to carry now
It flows more slowly than the youthful stage

31. 3 features/landforms of a mature river
Wider valley troughs
Meanders
Flood plain

32. Wider valley troughs
The sides of the mature valley are less steep and the floor is wider and flat
Lateral erosion widens the valley
The river swings from side to side, removing the interlocking spurs
Weathering and mass movement continues so the valley becomes less steep

33. Meanders

34. Meanders
Meanders are curves or loops that develop along the course of a river.
They are formed by both erosion and deposition.
As the river flows around a slight bend, the water on the outside bank flows more quickly and erodes the bank.
The water on the inside flows more slowly . As a result, it deposits its load.
This process continues and the meanders become more pronounced.
Examples include Shannon, Blackwater and the Moy

35. meander

36. Flood Plain

37. Flood plain

38. Floodplain
This is the land on either side of the river. It has a very covering of fertile clay called alluvium.
Following a period of heavy rainfall, the size of a river increases and it may overflow its banks to flood the land.
The water loses its speed and deposits a layer of alluvium

39. Old rivers
This is the last stage of the river and it flows slowly with little energy. It deposits its load because of this lack of energy and because the load is too heavy.
Features found at the old stage include:
Ox Bow lakes
Levees
Deltas

40. Ox Bow Lakes

41. How an OX BOW Lake is formed
An ox bow lake is a horse-shoe shaped lake that was once part of a meander
Erosion takes place on the outer banks of the river and in between the neck of 2 meanders
When the energy has a lot of energy it cuts through the neck to flow along a straight path
The river has little energy so it deposits its load along the channel
This eventually cuts off the meander to form an ox bow lake

42. Ox bow lake

43. Levees

44. levees Levees are raised banks of alluvium
When a river bursts its banks, it flows over the floodplain
It quickly loses its energy and deposits its heavier load close to the river
Smaller rocks/stones are carried further away
Over time the rocks build up along the river banks to form levees

46. Deltas

47. delta

48. A delta is formed when a river is about to enter the sea.
How a delta is formed
A delta is formed when a river is about to enter the sea.
The river loses speed and deposits its load.
Lighter material can be carried out to sea but the heavier load is deposited at the mouth of the river.
Over time the deposited rocks build up forming new land called deltas
The river is split into smaller channels called distributaries
not all rivers flow into the sea so there will be no delta  `v

49. River mississippi
The mississippi drains nearly 40% of the land surface of the USA
Over time man has interfered with the river in the following ways:
(A) building man made levees to prevent flooding
(B) cutting off meanders so the river flows straighter
THIS HAS EFFECTED THE RIVER IN MANY WAYS:
(a) levees have walls 8 metres high. The river cannot overflow its banks and deposit its load so instead the level of the river increases
The authorities built the levee walls even higher and this means that the river is now higher than the landscape

50. Floods (positives and negatives) Dam building and hydro electric power
Learning outcome
Floods (positives and negatives)
Dam building and hydro electric power

51. Quick pop quiz 3 stages of rivers? Source?Tributary? Confluence?
Rivers erode in 4 way?
Rivers transports in 4 ways?
Rivers overflow leaving deposits of
At which stage of a river is a waterfall found?

52. The flood of 2001 A example of the Mississippi flooding
In spring of 2001, many areas received three times the normal amount of rainfall
As the snow on the mountains melted, it fed the river mississippi, raising the level of the river
The river became so swollen, it broke some of the levees and flowed across the floodplains
What were the effects of the flooding?
Factories, houses, shops and businesses were flooded
60 people died
Crops were ruined and many animals were killed
Water supply and sewage systems were disrupted
Ships could not travel along the mississippi so this had economic consequences

53. How can rivers be useful to man?
Rivers provide excellent settlement sites for man. Many cities such as Dublin are built alongside the river Liffey
The river is a source of food and water.
Rivers are a means of transport: the river Rhine in Germany is used by barges to transport goods such as coal. This reduces traffic congestion on the roads
Rivers provide us with rich agricultural land
Rivers can be used to provide hydro electric power (HEP)
Rivers are also used for leisure activities such as……

54. What are the negative effects of rivers?
When rivers flood, it can cause death and destruction to farmland and property
Rivers can become polluted by man and this damages aquatic life.
For example: When farmers spread fertiliser or use pesticides on slopes (hills) when it rains, this runs down the hill and finds its way into rivers.

55. Dam building
A dam is a barrier constructed across a river to control the flow of the river
There are many advantages to dam building:
(1) hydro electicity power stations are built near the river and they use the energy from the water by converting it into electricity
(2) artificial lakes called reservoirs are built behind the dam and this water can be used as local water supply or for leisure activities
There are many disadvantages to dam building:
Sometimes as the level of water rises, areas are flooded and this means that homes are destroyed and agricultural land is lost
People have to relocate away from the dam
Fish farming can be effected due to the loss of spawning ground

56. Poulaphouca dam

58. Hydro electric power station

59. How is electricity created using water??
The theory is to build a dam on a large river that has a large drop in elevation.
The dam stores lots of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake.
Gravity causes it to fall through the penstock inside the dam.
At the end of the penstock there is a turbine propeller, which is turned by the moving water.
The shaft from the turbine goes up into the generator, which produces the power.
Power lines are connected to the generator that carry electricity to your home and mine.
The water continues past the propeller through the tailrace into the river past the dam. By the way, it is not a good idea to be playing in the water right below a dam when water is released!