Rivers

Common River TermsCommon 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 TermsCommon 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 JourneyThe River’s Journey

• Rivers usually begin in the mountains.

• They flow downhill onto flat land and into the sea.

The Shannon’s JourneyThe 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 JourneyThe 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 RiverThe 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 Erosion4 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 Erosion4 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 StageLandforms 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 ValleysV-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 ValleysV-Shaped Valleys

Interlocking SpursInterlocking 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

• 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.

WaterfallsWaterfalls

The Mature StageThe 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 TransportationRiver 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 TransportationRiver Transportation

• Transportation occurs in 4 ways.

• 1. Rolling

• 2. Bouncing

• 3. Suspension

• 4. Solution

River TransportationRiver Transportation

BouncingRolling

SuspensionSolution

RollingRolling

• Rolling – The large stones are rolled along the bed of the river.

RollingRolling

BouncingBouncing

Bouncing – The smaller pebbles are bounced

along the bed of the river.

BouncingBouncing

SuspensionSuspension

Suspension – Light material like sand and silt are

carried along (floating) in the water.

SolutionSolution

4. Solution – Dissolved materials are carried along by the river.

SolutionSolution

Landforms of the Mature Stage 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 StageLandforms 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 StageLandforms of the Mature Stage

Meanders

Meanders are bends or curves along the river. They are formed by erosion anddeposition. Erosion occurs on one side of the river while deposition occurs on the opposite side. This continues, making the bends sharper. See diagrams.

MeandersMeanders

Landforms of the Mature StageLandforms of the Mature Stage

Flood Plain

A flood plain is the flat area of land on either sideof the river. After heavy rain the river sometimesfloods. The water spreads out over the land oneither side of the river. When the river retreats itleaves behind a thin layer of alluvium. After manyfloods a thick layer of alluvium is created. This isvery fertile soil.

The Old StageThe 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 StageLandforms 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 StageLandforms of the Old Stage

Ox-Bow Lakes

An ox-bow lake is a horseshoeshaped lake found beside ariver. Ox-bow lakes are formedwhen continued erosion anddeposition create verypronounced meanders.

Eventually the river cuts throughthe neck of the meander.Deposition then occurs whichleaves the ox-bow lakeseparated from the river.

How an Ox-Bow Lake is MadeHow an Ox-Bow Lake is Made

Landforms of the Old StageLandforms of the Old Stage

Levees

Levees are raised banks of deposited materialfound along the banks of the river. When the riverfloods and spreads out over the floodplain, theheaviest material is deposited close to the river.Over time and after many periods of flooding thisdeposited material forms levees along the banks ofthe river.

Levees – Raised BanksLevees – Raised Banks

Landforms of the Old StageLandforms of the Old Stage

Delta

A Delta is a triangular shaped piece of landwhich is formed at the mouth of the river. Asthe river enters the sea it drops off all theremaining material it is carrying. Thismaterial builds up to form new land. The river isforced to break up into smaller channels calleddistributaries.

Rivers and PeopleRivers and People

Rivers have always been important forpeople. In the past, people settled near ariver as it provided them with food, water,defence, and an easy method of transport.

Nowadays, people try to control rivers toprevent 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)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.