River landscapes in the UK

What is a landscape?

An area's character that comes from the actions and interactions of natural and human elements

What is relief?

The way the landscape changes in height

What are upland areas?

Areas high above sea level, often mountainous

What are lowland areas?

Areas not very high above sea level, often flat

Where are the UK's upland areas located?

Mainly in the north and west (Northern Ireland, Scotland, Wales, northern England including Lake District, Grampian Mountains, Snowdonia)

Where are the UK's lowland areas located?

In the south and east (central and southern England, including Cotswolds, Norfolk, South Downs)

What is the source of a river?

Where the river begins

What is the mouth of a river?

The end of a river where it enters the sea or a lake

What is a tributary?

A small stream or river which flows to a larger river

What is a river bed?

The bottom of a river or stream

What is a river bank?

The sides of a river or stream

What is a river channel?

The physical confines of a river, consisting of a bed and banks

What is a watershed?

The boundary of a drainage basin

What is a drainage basin?

An area of land drained by a river and its tributaries

What is a confluence?

The point where two rivers meet

What is bedload?

The amount of sediment located at the bottom of the river

What is discharge?

The volume of water passing at a given point on a river at a given time

What is erosion?

The process that wears away the riverbed and banks and breaks up rocks carried by the river

What is vertical erosion?

Process that deepens the river valley making it V-shaped; dominant in upper course; causes intense downward erosion

What is lateral erosion?

Process that widens the river valley and channel; dominant in middle and lower courses

What is hydraulic action?

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

What is abrasion in rivers?

When materials carried by the river grind along the riverbank and bed in a sand-papering effect

What is attrition?

When material being carried by the river hits each other and pieces become rounder and smaller

What is solution (erosion)?

When rocks are dissolved by the slightly acidic water

What is traction?

When large particles like boulders are pushed along the riverbed by the force of the water

What is suspension?

When small particles like silt and clay are carried along by the water

What is saltation?

When pebble-sized, smaller particles are bounced along the riverbed by the force of the water

What is solution (transportation)?

Soluble materials dissolve in the water and are carried along

What is deposition?

When a river drops the eroded material it's transporting; happens when a river slows down (loses velocity)

One of the reasons affecting river erosion?

Volume of water falls

One of the reasons affecting river erosion. 1

Amount of eroded material increases

One of the reasons affecting river erosion, especially inside of a bend. 2

Water is shallower

One of the reasons affecting river erosion 3

River reaches mouth.

Long profile

Shows the gradient of a river from source to mouth.

Cross profile

Shows the shape of the valley from one side to another; like a slice through the land.

Gradient effect on erosion rate

Steep gradient means greater energy, increasing rate of erosion.

Bedload effect on erosion rate

More sediment, pebbles and rocks increases the amount of abrasion.

Human factors affecting erosion rate

Changing the landscape changes erosion rate (e.g. deforestation decreases time for water to reach river).

River management effect on erosion

Building concrete riverbanks can reduce erosion.

Flooding occurrence

When the capacity of the river channel is exceeded and water flows over the banks.

Lag time

The time taken for precipitation to reach the river from where it falls.

Lag time and flood risk

Shorter lag time = higher flood risk because discharge rises more quickly.

Porous material

A material that allows gases or liquids to pass through small pores.

Permeable material

A material that allows gases or liquids to pass through it (through pores or cracks).

Impermeable material

A material that prevents fluids from passing through it.

Deforestation and flood risk

Lack of trees reduces interception and infiltration, increasing overland flow risk.

Urbanisation and flood risk

Impermeable concrete and tarmac increase overland flow; water flows into drains reaching river rapidly.

Agriculture and flood risk

Bare soil and ploughing increase overland flow, especially where ploughing is downslope.

Climate change and flooding

Rising global temperatures may increase storm frequency and intensity.

Relief and flood risk

Steep slopes reduce infiltration and increase overland flow.

Rock type and flood risk

Impermeable rocks reduce percolation and increase overland flow.

Soil and flood risk

Frozen, saturated or compacted soil reduces infiltration; clay soils reduce infiltration and increase overland flow.

Weather and flooding

Heavy or prolonged rainfall exceeds infiltration rate leading to overland flow; rapid snow melt increases overland flow.

Seasonal variation and flooding in Northern Europe

Flooding tends to occur in autumn and winter when rainfall is more frequent.

Monsoons and flooding

Much annual rainfall occurs in few weeks, saturating ground and increasing overland flow.

Drainage density and flooding

High drainage density means many tributaries take water to main channel, causing rapid increase in discharge.