River landscapes and processes Geography CCEA GCSE 2009
The earth’s crust is modified by fluvial processes which result in distinctive landforms
The river cuts downward to form a ‘V’shaped valley. The river starts to meander
River uses its meanders to cut from side to side eating into the valley Floodplain starts to form 1 2
Floodplain River bluffs Alluvial deposits River cliff
River Processes A 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 Erosion • Abrasion – • 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 -
River Features • Rivers 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!
Why does it erode downwards? • How does it erode downwards?
Use this sketch to help explain how they form Vertical abrasion
Upper Course Also known as ‘Torrent’ or ‘Youth’ stages Interlocking Spurs In 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
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)
USA Canada Case study: Niagara Falls
Canada Horseshoe 750 meters
American Bridal Falls 330 meters