2. What is a river?
• A river is a natural watercourse,
usually freshwater, flowing
towards the sea.
• Without the hydrological cycle,
rivers cannot be formed.
5. HYDROLOGICAL CYCLE
• Precipitation – water
from clouds come to the
Earth’s surface as rain,
snow and hail
• Transpiration – plants
release water vapour into
atmosphere
6. HYDROLOGICAL CYCLE
•Surface Run-off – rain
that falls on Earth’s
surface flows over land
• Condensation – water
vapour rises, cools and
changes into tiny water
droplets
7. HYDROLOGICal CYCLE
• Infiltration – water
that soaks into the soil
subsurface
• Percolation – water
moves further down
into the underlying soil
after infiltration
9. RIVER SYSTEM
• Source – the
starting point of a
river
• Mouth – the ending
point of a river
• Drainage Basin –
The area drained by
a river and its
tributaries
10. RIVER SYSTEM
•Confluence – the
point at which a
tributary joins the
main river
• Watershed – The
boundary formed
by the edges of the
drainage basin
11.
12. Waterfalls
• Sudden, steep and vertical flow of fast-
flowing water falling from great heights
• Formed by river erosion
13. Niagara Falls on Niagara River,
Canada and USA
• formed by
erosion of
rock of
different
resistance
16. Formation of Waterfalls
• River erodes the less resistant rock more
rapidly
• This cause a change in the gradient of the river
course.
17. Formation of waterfalls
• Over time, river plunges from a great height to
hit the riverbed below,
• This forms a waterfall.
18. Formation of plunge pools
• Repeated pounding of the river bed leads to a
depression at the base of a waterfall
• A plunge pool is formed.
19. Meander
• A river that follows a
winding course, usually
forming hoop-like bends.
• River may meander
because
Lower gradient lower
speed lower river
energy river turns to
avoid obstacles
27. Floodplain and Levee
• During a heavy rainfall, river water
overflows its bank. River loses speed as it
encounters friction.
28. Floodplain and Levee
• Deposition occurs as river’s energy decreases.
• Coarser and heavier sediments are deposited
nearer to the river bank.
• Finer and lighter sediments are deposited
further away.
30. Floodplain and Levee
• Overtime, the accumulation of fine
sediments results in the formation of flat
plains
31. • Coarser and heavier sediments are
acculumated
• Results in the formation of raised banks
• Known as levees.
32. Formation of Delta
• At the river mouth, a river loses energy and
starts to deposit its sediments.
33. Formation of Delta
• As the
sediments build
up, the mouth
will be blocked
• The river also
split into several
small channels
called
distributaries to
flow to the sea.
35. Positive Impact of river
• Rivers provide water
for domestic
purposes such as
drinking, bathing and
washing.
• Rivers are a good
source of food such
as fish and prawns.
36. Positive Impact of river
• Rivers are important
waterways for
transporting people
and goods.
37. Negative Impact of river
• River water
overflows river
bank cause lives
to be lost and
destroy property
and crops.
• .
38. Negative Impact of river
• Consuming
contaminated
river water can
cause people to
fall ill
• Eg contract
diseases such
as cholera.
