Rivers

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					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.

				
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