Section C (1) - Rivers

What is a river?

Freshwater flowing downhill in a river channel from the source to mouth.

Is a river made up of freshwater or saltwater?

Freshwater

Does a river move downhill or uphill?

Downhill

Define: Source

Where a river begins.

Define: Mouth

The end of the river where it joins with a larger body of water.

Define: Confluence

The point where two rivers join.

Define: Tributary

Smaller rivers that join a main river.

Define: Watershed

The edge of a drainage basin.

Define: Drainage Basin

The area of land drained by a river and its tributaries.

Define: Estuary

When river freshwater mixes with the seas saltwater.

Define: Discharge

The volume of water in a river.

Define: Channel

The path a river flows in.

Define: Bedload

All the sediment in a river channel.

Where does a river begin and end?

Begins at the source

Ends at the mouth

What is the point at which 2 rivers meet?

Confluence

What are smaller rivers that join a main river?

Tributary

What is the edge of a drainage basin?

Watershed

What is the area of land drained by a river and its tributaries?

Drainage basin

What is a mix of freshwater and saltwater?

Estuary

What is the volume/amount of water in a river?

Discharge

What is the path a river flows in?

River channel

Define: Erosion

The breakdown/wearing away and movement of rock, such as the banks and bed of the river.

What is the breakdown/wearing away and movement of rock, such as the banks and bed of the river?

Erosion

Name the four types of erosion

• Hydraulic Action

• Abrasion

• Attrition

• Corrosion

Name the two directions of erosion

Vertical and Lateral

Which type of erosion acts in a downwards direction - eroding mainly the bed?

Vertical erosion

What type of erosion acts in a sideways direction - eroding mainly the banks?

Lateral erosion

Does vertical erosion act sideways or downwards?

Downwards

Does lateral erosion act sideways or downwards?

Sideways

Does vertical erosion mainly erode the bed or banks?

Bed

Does lateral erosion mainly erode the bed or banks?

Banks

Which direction of erosion occurs in the upper course?

Vertical erosion.

What is hydraulic action?

The power of flowing water into cracks in the rivers banks/bed, breaking pieces off and eroding it.

What is abrasion?

Small boulders and rocks scratch and scrape along the river’s bed/banks during transport, wearing away the banks and bed.

What is attrition?

Rocks knock and bang against each other, breaking pieces off and smoothing/rounding the rocks.

What is corrosion?

Dissolving of soluble rocks by chemicals in the river like chalk and limestone.

“The power of flowing water into cracks in the rivers banks/bed, breaking pieces off and eroding it.” - What type of erosion is this?

Hydraulic action

What type of erosion involves water getting into cracks in the rock?

Hydraulic action

“Dissolving of soluble rocks by chemicals in the river like chalk and limestone.“ - What type of erosion is this?

Corrosion

What type of erosion involves the dissolving of rocks by chemicals in the water?

Corrosion

“Rocks knock and bang against each other, breaking pieces off and smoothing/rounding the rocks.” - What type of erosion is this?

Attrition

What type of erosion involves rocks banging against each other?

Attrition

“Small boulders and rocks scratch and scrape along the river’s bed/banks during transport, wearing away the banks and bed.“ - What type of erosion is this?

Abrasion

What type of erosion involves rocks scraping along the rivers bed and banks?

Abrasion

Name the four types of river transport

• Solution

• Saltation

• Suspension

• Traction

What is traction?

Large heavy boulders are rolled slowly along the river bed by the force of the water.

What is saltation?

Pebbles are bounced along the river bed.

What is suspension?

Lighter sediment is suspended and carried within the water.

What is solution?

The transport of dissolved rock/chemicals.

“Large heavy boulders are rolled slowly along the river bed by the force of the water.” - Which type of river transportation is this describing?

Traction

What type of transport involves slowly rolling rocks along the river bed?

Traction

“Pebbles are bounced along the river bed.“ - Which type of river transportation is this describing?

Saltation

What type of transport involves rocks bouncing along the river bed?

Saltation

“Lighter sediment is suspended and carried within the water.” - Which type of river transportation is this describing?

Suspension

What type of transport involves sediment suspended in the river?

Suspension

“The transport of dissolved rock/chemicals.” - Which type of river transportation is this describing?

Solution

What type of transport involves dissolved chemicals/rocks?

Solution

What is deposition?

When a river loses energy, it drops any sediment it had been carrying during transportation.

When does deposition occur?

When velocity of the river drops so the river loses energy.

Freeze thaw weathering

Water gets into a crack in the rock, freezes and expands. The process repeats, weakening the rock and eventually making it fully breakdown.

Describe a long profile

A diagram showing the full length of the river and it’s gradient (steepness) from its source to its mouth. It shows how the river changes across all three courses.

Which profile shows the full length of the river and it’s gradient (steepness) from its source to its mouth?

Long profile

Describe a cross profile

A diagram showing a section of a river’s channel and valley sides. It shows the width, depth and banks of the river.

Which profile shows the width and depth of a river: its bed and banks?

Cross profile

Which profile shows the length of a river?

Long profile

Which profile shows a rivers gradient?

Long profile

What is the fastest flow back to the river?

Surface run off

What are the 3 processes in which water travels back to the river?

Surface run off, through flow and groundwater flow

Precipitation

Rain, hail, sleet or snow

Interception

Leaves/Trees catching the rain as it falls towards the ground

Inflitration

Water seeping into the soil

Percolation

Water seeping into the rock layer beneath the soil

Throughflow

Water flows through the soil back to the river

Groundwater flow

Water flows through the rock towards the river

What is it called when water seeps into the soil?

Infiltration

What is it called when water seeps into the rock layer beneath the soil?

Percolation

What is it called when water flows through the soil back into the river?

Throughflow

What is it called when water flows through the rock back into the river?

Groundwater flow

What type of rock does not allow liquid to pass through?

Impermeable rock

What type of rock allows liquid to pass through?

Permeable rock

Name the 3 courses of a river

Upper, middle and lower course

Describe the velocity, discharge, energy and shape in the upper course

• Low velocity

• Low discharge

• Low energy

• Narrow + Shallow + Steep

Describe the velocity, discharge, energy and shape in the lower course

• High velocity

• High discharge

• High energy

• Wide + Deep

Which course is narrow and shallow?

Upper course

Which course is wide and deep?

Lower course

What course is the source found in?

Upper course

What course is the mouth found in?

Lower course

Which course has the fastest velocity?

Lower course

Which course has the slowest velocity?

Upper course

Which course has the highest discharge?

Lower course

Which course has the lowest discharge?

Upper course

Why is velocity slow in the upper course?

Low discharge means there’s lots of friction between the rocks and water

Why is velocity fast in the lower course?

• High discharge so less friction between rocks/water

• Lots of energy means that the river moves quickly

Why does the width of a river channel increase as you move downstream?

Tributaries join + lateral erosion occurs

Why does the discharge of a river channel increase as you move downstream?

Tributaries join

Which type of erosion explains why sediment carried by a river becomes smaller as you move downstream?

Attrition

Does the upper or lower course have large, heavier sediment? Why?

Upper course. Erosion is yet to occur and break down rock.

Does the upper or lower course have finer, smaller sediment? Why?

Lower course. Erosional processes such as attrition break down the rock.

Why does the depth of a river channel increase?

Vertical erosion

Why does the size of sediment tend to decrease downstream?

More erosion - especially attrition which reduces the size of sediment