Rivers Flashcards
What percent of the worlds water is found in seas and oceans?
97%
What is a drainage basin?
The area of land drained by a river
What is the catchment area?
The area within the drainage basin
What is the watershed?
The boundary between two or more drainage basins
Where are watersheds usually found?
The edge of highlands surrounding a drainage basin
What is a confluence?
The point at which two rivers or streams join together
What is a tributary?
A stream or smaller river which joins a larger river
Describe a cross section of the land near to the source of a river
V-shaped valley Narrow and shallow river
What is the name of the process that causes a river to erode downwards?
Vertical erosion
Name the four main forms of erosion
Hydraulic action Solution Attrition Abrasion
Explain hydraulic action
The force of the river causes air to be trapped in cracks of the bank. This pressure weakens the banks and slowly causes them to wear away
Explain abrasion
Erosion caused by the rubbing of materials carried by rivers
Explain attrition
Erosion caused when rocks and boulders transported by rivers and waves bump into each other and get smaller
What does attrition do to the size of the rocks?
Smaller Smoother Rounder
Name the four different transport processes in rivers
Solution Suspension Traction Saltation
Explain solution for erosion and transportation
Small pieces of rock and minerals are dissolved in the river and then carried along
Explain suspension
Fine, light materials are carried along the water
Explain saltation
Small pebbles and stones bounce along the river bed
Explain traction
Larger rocks and boulders are rolled along the river bed
What is required for traction to occur?
High energy level in the river
Where are energy levels usually at their highest in a river?
In the lower course
What causes deposition?
The river losing energy : Inside of a meander
Estuary
Where is deposition the most common?
Near to the mouth Shallow areas Low volume of water
Name the upper course features
-V shaped valleys -Interlocking Spurs -Rapids -Waterfalls -Gorges
Name the features of the middle course
-Wider, shallower valleys -Meanders -Oxbow lakes
Name the features of the lower course
-Wide, flat bottomed valleys -Floodplains -Levees -Deltas
Why do interlocking Spurs occur?
The river avoids areas of hard rock due to its low energy
How does a waterfall occur?
-A layer of hard rock above a thicker layer of soft rock causes the soft layer to erode faster -The soft rock slowly undercuts the hard rock due to it eroding faster and a steep edge is created -This overtime develops to be a waterfall as the height difference increases -Eventually the overhanging rock falls and the waterfall slowly retreats
How do Rapids form?
Ridges of hard rock cause an uneven slope. This creates Rapids
Why does water travel faster in the middle course compared to the upper course?
The channel has been widened and deepened and therefore less friction
Why do meanders form?
-The river erodes laterally -Deposition on inside -Erosion on outer side
What happens on the inside bend of a meander?
-The river flows slower -Material is deposited -More friction
What happens on the outside bend of a meander?
-Water erodes and undercuts the bank -Most energy -Less friction