Rivers
Common River Terms
• Source – The place where a river begins.
• Course – The route the river takes to the
sea
• Tributary – A small river that joins a larger
river.
• Confluence – The point where the
tributary joins the river.
Common River Terms
• Mouth – The point where the river enters
the sea.
• Estuary – The part of the mouth that is
tidal.
• Basin – The area of land drained by a
river.
• Watershed – The high ground separating
one river basin from another.
The River’s Journey
• Rivers usually begin in the mountains.
• They flow downhill onto flat land and into the sea.
The Shannon’s Journey
• The River Shannon is
Ireland’s longest river.
• It flows from the Cuilcagh
Mountains in Co. Leitrim
to the Atlantic Ocean on
the west coast of Ireland.
The Stages of a River’s Journey
• As the river flows from it’s source to the sea it goes through 3
stages. These are,
• The Upper or Youthful Stage
• The Middle or Mature Stage
• The Lower or Old Stage
The Youthful River
• The youthful river has a small amount of
water but it travels very quickly down the
steep mountain slope.
• Most of its energy is used to erode (wear
away) the landscape.
• This erosion (wearing away) occurs in 4
ways.
4 Processes of River Erosion
• Hydraulic Action – The force of the
moving water wears away the banks and
bed of the river.
• Abrasion – Small stones carried by the
river wear away at the the banks and bed
of the river.
4 Processes of River Erosion
• Attrition – The small stones in the river
are worn down and broken up as they hit
off each other.
• Solution – Rocks and soil are dissolved
by acids in the water.
Landforms of the Youthful Stage
•
All of the erosion by the river creates features
or landforms on the landscape.
Three features created in the youthful stage are,
1. V-shaped Valleys
2. Interlocking Spurs
3. Waterfalls
V-Shaped Valleys
• V-shaped valleys get their name from their
shape. The river erodes the landscape and
creates a valley in the shape of a V.
• This occurs because of Vertical Erosion. The
river cuts down into the river bed, making it
deeper. It creates a narrow deep valley.
Mechanical weathering and mass movement
create the V shape. See Diagram.
V-Shaped Valleys
Interlocking Spurs
• As the rivers flows it meets areas of hard
rock. It cannot erode these so it flows
around them.
• This creates a zigzag course. See
Diagram.
Waterfalls
• Waterfalls are formed when
rivers flow over areas of hard
and soft rock.
• The river erodes the soft rock
but cannot erode the hard
rock. This creates a step which
the water starts to fall over.
• The falling water erodes
deeper into the bed. The rivers
load creates a Plunge Pool as
it falls. See Diagram.
Waterfalls
The Mature Stage
• We now know that during the youthful stage the
river is mainly eroding the landscape.
• Erosion breaks off particles of rock and soil from
the bed and banks of the river. They are carried
along by the river and are known as the Load.
• The load is carried from upland to lowland
areas. This process is called River
Transportation.
River Transportation
All rivers carry material in them. This material is carried by
the river as it flows along.
Rivers can carry large stones, small stones, sand, and
other dissolved minerals.
All of this material in the river is called the river’s Load
When the river moves its load we call this River Transportation
River Transportation
• Transportation occurs in 4 ways.
•
•
•
•
1. Rolling
2. Bouncing
3. Suspension
4. Solution
River Transportation
Suspension
Solution
Rolling
Bouncing
Rolling
• Rolling – The large stones are rolled along the
bed of the river.
Rolling
Bouncing
Bouncing – The smaller pebbles are bounced
along the bed of the river.
Bouncing
Suspension
Suspension – Light material like sand and silt are
carried along (floating) in the water.
Solution
4.
Solution – Dissolved materials are carried along by
the river.
Solution
Landforms of the Mature Stage
In the Mature Stage the river begins to slow down,
and so it begins to deposit some of its load. It
creates the following features.
1. Wide river valley
2. Meanders
3. Flood plain
Landforms of the Mature Stage
Wider River Valley
In the mature stage the river moves from
side to side and the valley becomes wide
and flat. Weathering and Mass Movement
continue to wear away at the sides of the
valley. See diagram.
Landforms of the Mature Stage
Meanders
Meanders are bends or curves along the river. They are formed by erosion and
deposition. Erosion occurs on one side of the river while deposition occurs on
the opposite side. This continues, making the bends sharper. See diagrams.
Meanders
Landforms of the Mature Stage
Flood Plain
A flood plain is the flat area of land on either side
of the river. After heavy rain the river sometimes
floods. The water spreads out over the land on
either side of the river. When the river retreats it
leaves behind a thin layer of alluvium. After many
floods a thick layer of alluvium is created. This is
very fertile soil.
The Old Stage
• In the Old Stage the river is
carrying lots of sand and
silt. It is now flowing over
flat land and so it is moving
slowly. Therefore it begins
to drop off its load. This is
called deposition. Like
erosion in the Youthful
Stage, deposition also
creates many features or
landforms.
Landforms of the Old Stage
The following features or landforms are
created by river deposition in the Old Stage.
1. Ox-Bow Lakes
2. Levees
3. Delta
Landforms of the Old Stage
Ox-Bow Lakes
An ox-bow lake is a horseshoe
shaped lake found beside a
river. Ox-bow lakes are formed
when continued erosion and
deposition create very
pronounced meanders.
Eventually the river cuts through
the neck of the meander.
Deposition then occurs which
leaves the ox-bow lake
separated from the river.
How an Ox-Bow Lake is Made
Landforms of the Old Stage
Levees
Levees are raised banks of deposited material
found along the banks of the river. When the river
floods and spreads out over the floodplain, the
heaviest material is deposited close to the river.
Over time and after many periods of flooding this
deposited material forms levees along the banks of
the river.
Levees – Raised Banks
Landforms of the Old Stage
Delta
A Delta is a triangular shaped piece of land
which is formed at the mouth of the river. As
the river enters the sea it drops off all the
remaining material it is carrying. This
material builds up to form new land. The river is
forced to break up into smaller channels called
distributaries.
Rivers and People
Rivers have always been important for
people. In the past, people settled near a
river as it provided them with food, water,
defence, and an easy method of transport.
Nowadays, people try to control rivers to
prevent flooding, for irrigation, to create electricity
(HEP), and to create improved transport links.
Rivers are also important for tourism and leisure.
Hydro-Electric Power (HEP)
Engineers build dams across
the river.
They can then control the
flow of water in the river.
They release the water and
use it’s power to turn large
turbines.
Turning these turbines
creates power which is used to
generate electricity.