River landscapes and processes Geography CCEA GCSE 2009

The earths crust is modified by fluvial processes which result in distinctive landforms

Stages in the Development of a River Valley

The river cuts downward to form a Vshaped valley.The river starts to meander

What happens next?

River uses its meanders to cut from side to side eating intothe valleyFloodplain starts to form12

What happens next?

12

What happens next?

FloodplainRiver bluffsRiver cliffAlluvialdeposits

River ProcessesA river process is something that happens in the river. The main processes in the river are

Erosion - where parts of the river bed and bank get eroded / removed from the landscape Transportation - where the eroded material is carried from one place to another through the river system Deposition - where the river load becomes too heavy for the river to carry and is dumped down / deposited.

A river can erode material from its bed and banks in 4 main ways Abrasion Moving water throws particles it is carrying against the bed and banks of the river which dislodges more material Hydraulic Action - The sheer force of the water pounding into the bed and banks can dislodge material Attrition - Particles being carried downstream knock against each other, wearing each other down. This results in smaller, rounder particles as you move downstream

Use your text book to see if you can find the 4th type!

Methods of ErosionAbrasion

Hydraulic Action -

Attrition -

Solution-

Methods of Transportation Rivers transport material in 4 main ways Solution - Some minerals (particularly in limestone areas) dissolve easily in water and are not visible to the naked eye Suspension As the speed or velocity of a river increases, it is able to pick up and carry larger and larger particles in its flow. Where particles are carried along in the flow and are not in contact with the river bed, they are said to be travelling in suspension.

Methods of Transportation Saltation - Heavier particles may not be held in the flow all the time but may be bounced along the bed Traction - The heaviest particles are rolled along the bed. Such particles may only be moved when the river has a large volume of water in it

Methods of Transportation

Solution -

Suspension-

Saltation -

Traction -

solution

River FeaturesRivers are eroding, transporting and depositing constantly within the drainage basin system. The river can be divided into 3 sections Upper Course at the Source, Middle Course and Lower Course at the Mouth of the river. The river displays different characterisitics at each section

How to take notes on each of the River Features! Course: Upper / Middle / Lower Feature: Eg Waterfall Diagram to illustrate: (make sure that this is labelled!)

Notes to explain how the feature happens:

Example of this feature: Make sure that you take a new page for each new feature!

The V - Shaped Valley

Can you mark the V-shaped valleys on these photos?

http://www.school-portal.co.uk/GroupDownloadFile.asp?file=55027&Groupid=12426

How are V-shaped valleys formed ?

Why does it erode downwards?How does it erode downwards?

Use this sketch to help explain how they form

Vertical abrasion

Also known as Torrent or Youth stagesInterlocking SpursIn the Upper Course, the river is fast flowing, but there is little water and load. The river is often called a stream and does not have the erosive power to remove the hillsides (spurs), but erodes downwards instead.EROSION TYPE: Vertical and Headward

Waterfalls and Gorges

Draw the stages in the formation of a waterfall

Explain in as much detail what is happening at 3

3. What is happening here? (see next slide)

Waterfall formation flash

Case study:Niagara Falls

Canada USA

Canada Horseshoe 750 meters

52 meters high

American Bridal Falls 330 meters

Both fallsthe falls help to produce HEP

The falls erode back at a rate of 1.5 meters a year

Frozen Falls

20 million visit the falls every year Visitors !!!

The Falls were stopped in 1969 to see if debris could be removed to improve the look !!

Hard Resistant Rock - Limestone Weak Rock - Shale 52 meters

Gorges (Upper & Middle Course)

Case study: Niagara Falls (USA and Canada)

http://www.school-portal.co.uk/GroupDownloadFile.asp?file=55026&Groupid=12426

Waterfall and Gorge 1(OBLIQUE AERIAL VIEW)EROSION TYPE: Vertical and Headward

Waterfall and Gorge 2(PROFILE VIEW)EROSION TYPE: Vertical and Headward

Use the Niagara Falls Pictures PowerPoint Notes to be taken from Page 10 from the Green Connections books

Meanders

1. Can you mark the fastest flow on this?2. What type of erosion do you think is happening?

..can you mark on this the fastest flow?

What is a meander?

where do you think erosion would take place?

What is a meander

Can you draw a cross section x-y?

What is a meander?

this is what a cross section through a meander looks like

What is a meander?

Meanders are formed because the current swings to the outside of a bend and concentrates the erosion there. Deposition occurs on the inside of the bed where there is not enough energy to carry load.EROSION TYPE: LateralAlso known as the Mature stageMeanders 1(Aerial View)

Meanders 2(Profile View / Cross Section X - Y)EROSION TYPE: LateralThis cross section clearly shows the eddy current (near X) formed by the velocity of the river being concentrated on the outside of the bend. These UNDERCUT the bank causing the formation of a RIVER CLIFF. On the inside (NEAR Y), a SLIP-OFF-SLOPE is formed where current is too slow to carry any load.

this is what a cross section through a meander looks like

What is a meander?

Ox- Bow Lakes (Middle Course)

Can you annotate this photo graph ?

Can you annotate this photo graph ?

Can you annotate this photo graph ?

Can you annotate this photo graph ?

What are Flood Plains and levees?

Floodplain Levees

. What do you think might happen here?

What is Meander Migration

What is Meander Migration

Ox-Bow Lake 1(Aerial View)EROSION TYPE: LateralOx-bow lakes are formed when two meander RIVER CLIFFS are being eroded towards each other. These will eventually meet, causing the river to then flow across the bottom of the diagram.

Ox-Bow Lake 2(Aerial View)

Levees

LeevesRiver

Leves and Raised Beds 1(Front View)DEPOSITION FEATURE: no erosion in the Lower CourseLeves are formed when rivers flood. The river water overflows the banks of the river and immediately slows down due to friction with the FLOODPLAIN. This drops the larger particles first, building up a raised river bank called a LEVE.

Leves and Raised Beds 2(Front View)DEPOSITION FEATURE: no erosion in the Lower CourseRaised beds form in the Summer months when the river volume and energy are low and load is dropped onto the river bed. The bed raises up and the capacity of the river reduces, causing flooding in the winter. This in turn builds up the leves and the whole process raises up the level of the river in the landscape.

Braided Channels(Oblique Side View)DEPOSITION FEATURE: no erosion in the Lower CourseIn the Summer months, load is dropped by the low volume of low-energy water in the river. These build up to form obstructions in the river and it divides up to flow around them. In the winter, it is likely that the river volume will increase and remove these obstructions.

Deltas

Delta(Aerial View)This deposition feature is one of the largest. When the flowing river hits the non-flowing sea, energy is suddenly lost. This causes all of the load in the river to drop in the river MOUTH. This builds up over time to create a delta an area of land. The river divides into DISTRIBUTARIES to continue to the sea, which is now some way away from its original meeting point.

Can you work out what the river is trying to do by using this diagram?

Can you work out what the river is trying to do by using this diagram?