1. Factors affecting energy of river Factors affecting former factor Description
The steeper the channel, the
greater the amount of GPE
Gradient of channel
conversion and the faster the
water moves down the channel.
The smoother the channel, the
lesser the amount of friction
Roughness of channel opposing motion of the water and
Speed of river
the faster the water moves down
the channel.
The lesser the wetted perimeter,
the lesser the amount of friction
Wetted perimeter opposing motion of the water and
the faster the water moves down
the channel.
The larger the drainage basin,
the greater the area for collection
Size of drainage basin
of rainwater and the fuller the
river would be.
The less vegetation, more surface
runoff occurs and less infiltrat-
Presence of vegetation ion takes place and the more
water flows into the river making
it fuller.
Volume of river
The less permeable the rocks,
less infiltration occurs and more
Permeability of rocks surface runoff takes place and
more water flows into the river to
make it fuller.
The more the rainfall the lesser
Climate amount of water reaches the
ground and make it fuller.

2. Process Subprocess Description
Agent: Running water
Force of fast moving water
Hydraulic action loosens rocks and soil along river
banks and bed, are soon dis-
lodged.
Agent: River bed and sides
When rock fragments are
Abrasion dragged along the river bed or
against the sides of the river,
grinding action causes widening
and deepening of channel.
Erosion
Agent: Other eroded particles
Eroded materials collide against
Attrition one another and this breaks them
down into smaller pieces, larger
rocks are slowly broken down,
rough edges are smoothened.
Agent: Carbonic acid
CO2 reacts with H2O to form
Solution H2CO3. When river flows over
limestone, carbonation occurs
and the acid dissolves the lime-
stone.
Heaviest materials tpted this way.
Traction
Dragged/rolled along river.
2nd heaviest tpt this way.
Saltation
Series of bouncing motions.
Transportation
Lightest materials tpted this way.
Suspension
“Float” along in water.
Soluble subs tpted this way.
Solution Transporting of dissolved
materials.

3. Factors that can cause deposition:
1. During low precipitation
2. River enters lake or sea,
decrease in speed
Deposition ------- 3. Increased friction with river
sides, decreasing the speed
4. Sudden increase in load, esp
during landslides
5.Obstructions (eg. aquatic life)
are present
DEPOSITION:
Small decrease in speed of river enables large
particles to be deposited while a large decrease
in speed enables smaller particles to be
deposited.
TRANSPORTATION:
Large particles require high river speeds to
transport them while smaller particles require
small river speeds to transport them.
EROSION:
From 0.5mm onwards, more energy is required
to erode the particle. Below 0.5mm, more
energy is required to erode them as these fine
particles are highly cohesive and they stick to
each other hence a large amount of energy is needed to dislodge them away from each other.
Formation of waterfall
1. When a river flows over rocks of different resistance, the less resistant rock is eroded far more
than the more resistant rock, causing a change in gradient of the river course. Over time, the river
plunges from a great height to hit the river below with tremendous force. A waterfall forms as a
results. Repeated poundings of the river bed may leave a depression at the base of the waterfall.
This depression is deepened as rocks and boulders swirl around forming a plunge pool.

4. 2. Due to the displacement of rocks, there is a difference in height between the two rocks. Water
cascades down the scarp to hit the lower rock. Repeated poundings of the river bed may leave a
depression at the base of the waterfall. This depression is deepened as rocks and boulders swirl
around forming a plunge pool.
Formation of gorges
When a river flows through an area with resistant rocks by its sides, it can only erode its channel
vertically. Over time, a deep, narrow and steep-sided valley known as a gorge is formed.
Formation of valleys
Upper course valley:
Gradient is steep hence it has sufficient energy to erode the rocks in its path and cut deep into the
channel. A V-shaped, narrow and steep-sided valleys are formed.
Middle course valley:
Gradient is not that steep hence it flows with less energy and cuts less deeply into its channel.
Lateral erosion is more dominant than vertical erosion hence it is wider.
Lower course valley:
Exceptionally wide because gradient is gentle. Lateral erosion is dominant giving rise to a broad,
flat-floored valley.
Formation of floodplains and natural levees
When there is heavy rain, a river may overflow its banks. This causes land on either sides of the
river to be flooded. As floodwater spread over large areas, it loses speed. When the floodwaters
recedes, the river deposits the material it is carrying on the land, leaving behind alluvium on the
river banks. Coarser sediments end up nearer the banks as they weigh more hence the
accumulation of these sediments form natural levees while the wide flat plains are the floodplains.

5. Formation of meanders and ox-bow lakes
In the outer bend of a river, the river flows faster than in the inner bend as there is less friction
against the water and the river sides. This causes erosion to occur in the outer bend due to high
speeds and deposition to occur in the inner bend due to the slows speeds. When more sediments
are eroded on the outer bend and more sediments are deposited on the inner bend, the river
become more curved, forming meanders.
With continual erosion and deposition, the meanders become more pronounced and curved
towards each other and a narrow neck of land forms in between the curve. With even more
deposition and erosion, the meanders will meet and soon damn up the water in the cut-off
forming an ox-bow lake. The water in the lake will soon evaporate away.
Formation of deltas
When a river approaches a sea, its speed decreases. Thus it deposits its sediments at the river
mouth. If the rate of deposition is greater than the removal of the sediments, they will accumulate
and build up at the river mouth. A delta is formed. When more alluvium is deposited, the delta
extends seawards and smaller channels known as distributaries are formed.

6. Method Description + - Example
Straightening of river Reduces chances Flooding down-
channel by removing of flood as there is stream may
meanders and curves in no chance for occur as these
the river. Reduces length deposition to eroded sedi-
River re-
of river. reduce depth of ments would be -------
alignment
river. deposited at the
lower course
where speed is
slow.
Widening and deepening Reduces chances Expensive to The Singapore
of the river channel to of flood as more carry out and it is River has been
increase ability to water is required not possible for re-sectioned
contain water. Wetted to cause the flood. LDCs to afford. during the post-
Re-sectioning perimeter is smoothened Difficult to carry independence
with cement and granite. out in urban years to increase
areas as there is the volume of the
a high demand river.
for land.
Walls of sand, stone and Reduces chances Easily over- China has built
concrete built along river of flood as more topped by a dykes along the
banks to increase water is required larger flood, Yellow River but
capacity of river. to cause the flood. expensive to has failed due to
construct and constant
Dykes
maintain. deposition of
sediments in the
river bed that
decreases the
depth.
Metal cages filled with Divert the flow of Metal cages rust
rocks placed at the river water to the cen- easily and when
sides. tre of the channel they are spoilt,
to prevent erosion they are useless.
Gabions
of the river sides, Short term pro- --------
no deposition of tection.
sediments to cause
floods.
Walls made up of large Divert the flow of Undermining of
stones that line the banks water to the cen- base of revet-
of a river. tre of the channel ments cause it to
to prevent erosion collapse
Revetments --------
of the river sides, eventually.
no deposition of
sediments to cause
floods.

7. Roots of trees hold the Channel does not Trees might Royal Forest
soil together firmly. Veg become shallower block the Department
slows down rate of hence chance of sunlight from (RFD) in
surface runoff, preventing flood is reduced. other aquatic Thailand came
Planting
large amounts of water plants in the up with
vegetations
from entering the river. river, affecting watershed
Decreases amount of the river management
eroded sediments into the ecosystem. programme to
river. prevent floods.