The Natural Environment: rivers

Evaporation

Liquid to gas

Condensation

Water vapour to liquid

Transpiration

When plants release water vapour from their leaves

Evapotranspiration

The combined transfer of water vapour from the earths surface and plants

Precipitation

The transfer of water from the atmosphere to the earths surface in the form of hail sleet snow or rain

Overland flow

Water flowing across the earths surface

Infiltration

When the water moves down from the surface into the soil

Percolation

The transfer of water down into the rocks or aquifers

Through flow

The movement of water through the soil

Groundwater flow

The flow of water through rock

What is a drainage basin

The system by which water is emptied to a point it can be collected

What is the number of tributaries in a drainage basin referred to as?

Drainage density

Drainage basins with a lot of tributaries have a __

high drainage density

Watershed

The boundary between drainage basins

Source

Where the river starts

Confluence

The place where two or more rivers/streams meet

Tributary

A stream or river flowing into a larger stream or river

Mouth

Where the river enters the sea/ocean

Hydraulic action

The force of water which removes material from the bed and banks of a river

Abrasion

When the materials carried by the river scrape away the banks and bed

Attrition

When the material being carried by the river smash into each other and wear each other down

Corrosion (solution)

When the rocks are dissolved by the slightly acidic water

Where does vertical erosion take place

upper course of river

Where does lateral erosion take place

middle and lower course of river

Traction

When larger rocks and material are rolled along the river bed

Saltation

When smaller material which can be lifted by the water bounces along the river bed

Suspension

Fine light materials being carried within the river flow

Solution

When materials are dissolved in the river water

Deposition

When a river does not have enough energy to carry materials so it drops them

What material gets deposited first

The heaviest, known as the bedload

Characteristics of the upper course of a river

* Shallow
* Steep valley sides - faster flowing water
* Narrow
* Low velocity
* Large bedload
* Vertical erosion
* V-shaped valleys
* Potholes

Characteristics of the middle course of a river

* Land not as steep
* Still v-shaped - wide v
* More tributaries - wider river
* Increased volume of water
* River is starting to meander

Characteristics of lower course of a river

* River is much wider - lateral erosion
* Oxbox lakes
* Volume of water is greater
* Gently sloping - mainly flat
* Slow flowing
* Lots of deposition

How are v shapes valleys formed

Hydraulic action

How are interlocking spurs formed

In the upper course of the river the channel begins to meander and erosion happens on the outside of the bend

How are rapids formed

Created by vertical erosion and traction

How are potholes formed

By a circular current with pebbles due to abrasion

What is a gorge

When the waterfall moves back, narrow, vertical steep walls are created, which is known as a gorge

What is discharge

The volume of water flowing through a river channel (measured in cubic metres/second)

What is a floodplain

Flat land surrounding a river

Name hard engineering methods (4)

* Dams or reservoirs
* Embankments or levees
* Flood relief channels
* Straightened channels

Name soft engineering methods (4)

* River restoration
* Flood plain zoning
* Afforestation
* Wetland conservation