River Characteristics,

Changes & Landforms

CatchmentThe area from which water drains into a particular drainage basin.

Tributary A river which joins a larger river.

ConfluenceThe point at which two rivers join.

Watershed The boundary dividing one drainage basin from another- a ridge of high land.

What is a drainage basin?

SourceThe upland area where the river begins.

MouthWhere the river flows into the sea, or sometimes a lake.

Watershed

Tributary

Features of a drainage basin on a map.

Confluence

a

b

c

Source

d

The Long Profile of a River

Changes in the river as it goes downstream from source

to mouth.

Long ProfileH

eig

ht

abo

ve s

ea l

evel

in

m

eter

s.

0 5

0 1

00

150

200

25

0

35 30 25 20 15 10 5 0

Distance from sea in Kms.

Gradient/slope decreasing

Velocity/flow increasing

Cumecs/discharge increasing

Energy increases

AUpper Course

BMiddle Course C

Lower Course

Valley & Channel Cross-Sections

A

Upper Course

B

Middle Course

C

Lower Course

Upper Course Middle Course Lower Course

Long ProfileSteeply sloping towards the lower sections of the river

Shallow slopes towards the mouth of the river

Almost at sea level, very gently sloping towards its

mouth

Cross ProfileSteep sided v-shaped

valley. Thin river channel, deep in places

v-shaped valley remains with a wider valley floor and the

river begins to meander across it. The river channel begins to widen and become

deeper.

Wide, shallow valley, with large flood plains and

meanders. The river channel is wide, deep and smooth

sided.

Erosion & Deposition

Primarily vertical erosion, through attrition, abrasion

and hydraulic action. Large boulders deposited and

eroded in situ.

Continues to cut vertically. But it also begins to cut

laterally as it gets closer to base level. Deposition occurs in the slower moving insides

of meanders.

Primarily cuts laterally as it has almost reached base

level. The erosive energy of the river is almost totally concentrated on cutting

sideways. Much deposition occurs.

Transportation Traction and saltationSaltation, suspension and

solutionMainly suspension and

solution.

FeaturesInterlocking spurs;

waterfalls; V-shaped valley; gorges

Meanders; slip-off slopes; ox-bow lakes

Deltas; flood plains; levees; meanders; ox-bow lakes

Velocity

Relatively slow moving. Despite areas of fast

flowing water, the large amount of material on the river channel bed means that friction will slow the

water down.

The water has increased in speed as the channel widens

and becomes smoother. Some boulders cause friction

to slow it down a little.

The fastest section of the river, as the channel is

widest, with very smooth sides, and the greatest

volume of water.

What are the main features of a river?

The Upper Course of a river

Learning Objectives: •To know and understand the formation of landforms in a river’s upper course.•To understand the processes that operate in a river’s upper course

What processes occur in a river?

There are 3 processes taking place in every river. These are:

Erosion

Transportation

Deposition

(The wearing away of the land)

(The movement of eroded material)

(The laying down of eroded material)

There are also two other processes that shape the river valley. These are weathering and mass movement.

Shaping the river valley.

There are also two other processes that shape the river valley. These are weathering and mass movement.

Weathering = the breakdown of rock material.

Mass movement = the movement downslope of broken down rock material due to gravity.

Weathering & Mass Movement.

The 3 main types of weathering are show below in the wrong order. Sort the statements out into the right order and copy these onto your sheet. Underneath copy out a definition of mass movement.

Erosion ProcessesMatch up the key word with the

definition.

• is when the river is loaded with material in suspension and scours away at the river banks. (Sandpaper effect)

• is the shear force of the river impacting on the sides of the river banks.

• is substances carried in solution such as acids. They dissolve rocks away over long periods of time.

• is when bed load collides into each other with the current flow and breaks down into smaller particles.

Abrasion (Corrasion)Abrasion (Corrasion) - - Hydraulic Action Hydraulic Action --

CorrosionCorrosion - - AttritionAttrition --

Erosion ProcessesMatch up the key word with the

definition.Abrasion (Corrasion)Abrasion (Corrasion) is when the river is loaded

with material in suspension and scours away at the river banks. (Sandpaper effect)

Hydraulic ActionHydraulic Action is the shear force of the river impacting on the sides of the river banks.

CorrosionCorrosion is substances carried in solution such as acids. They dissolve rocks away over long periods of time.

AttritionAttrition is when bed load collides into each other with the current flow and breaks down into smaller particles.

Key words - Transportation.

• Traction – where large rocks and boulders are rolled along the river bed. Happens most in times of flood, when the current is strongest.

• Saltation – where smaller stones are bounced along the river bed in a leap frogging motion

• Suspension – where very small grains of sand or silt are carried along with the water

• Solution – where some material is dissolved (like sugar in a cup of tea) and is carried downstream. Occurs often in limestone landscapes where the water if very acidic.

Methods of transportation.

Traction Saltation Suspension Solution

Shows the rate of flow needed

Upper valley characteristics

Upper valley characteristicsCan you add an annotation to each arrow to

explain the characteristic?

Upper valley characteristics

“V”shape valley, vertical erosion dominant

Interlocking spurs

Slumping and landslides - very active hill slopes

Narrow, shallow channel, low velocity and discharge

Large bed load derived from upstream and from valley sides

Narrow Channel

Lots of tributaries

High land so source of river

Contour lines close together – steep valley sides

Steep river gradient – contours close together

Direction of flow shown by lower land

No flood plain and V-shaped valley

1 2

3 4

Interlocking spurs A typical upper course V-Shaped valley with interlocking spurs, steep valley sides and active slope processes.

The diagram below shows the formation of interlocking spurs.

Can you draw an annotated sketch of this valley to show how it is formed?

River load in upper course

Boulders are large and semi-rounded, due to attrition within the load and abrasion with the stream bed and banks

Why are they rounded?

Rapids in the Upper Tees Valley

Formation of Rapids

High Force waterfall, R. Tees

WHAT IS A WATERFALL?

A waterfall is formed where water flows over a cliff or very steep drop in the river's bed.

High Force Waterfall R. Tees

Formation of a Waterfall.• A waterfall is a steep drop in the course of a river.

• They form when a band of hard resistant rock (cap rock) lies over softer, less resistant rock.

• The softer rock is quickly eroded by hydraulic action and abrasion, causing the harder rock to be undercut.

• The hard rock overhangs until it can no longer carry its own weight.

• The overhang collapses and then breaks up in the water below.

• The great power of the water at the base of the waterfall causes a plunge pool to form.

• The bed of the river below the waterfall contains boulders eroded by splash back from behind the waterfall.

• Over time the process above is frequently repeated and eventually a steep-sided gorge forms as the waterfall retreats up stream.

Waterfall formationLook at the diagram, How is a waterfall formed?

Can you put the labels below into the correct place on he diagram?

High Force waterfall, R. Tees

Waterfalls create a gorge upstream as they recede, This is a steep sided valley with no floodplain.

Upper Course of a River

Land use:Few settlements, Recreation, Farming, Forestry

Steep valley sides

Evidence of tributaries

Reservoir

High land

Narrow channel and no floodplain

Waterfalls

The Middle and Lower Course of a River

•To understand the main processes that operate in the middle and lower course of a river.•To understand how meanders and oxbow lakes are formed.

Learning Objectives

This is a picture of a river in its middle course. Can you recognise and explain the differences between the upper and middle course of a river?

Erosion is still an important process.

The river is now flowing over flatter land and so the dominant direction of erosion is lateral (from side to side).

The river has a greater discharge and so has more energy to transport material. Material that is transported by a river is called its load.

Deposition is also an important process and occurs when the velocity of the river decreases or if the discharge falls due to a dry spell of weather.

Processes operating in the middle course of a river

•Meanders

•Oxbow Lakes

DEPOSITION and EROSION create these landforms

What landforms are found in the middle course?

A meander= a bend in a river

Deep water A gently sloping area of land on the inside of a meander

Slip off slope Formed on the outside bend of the meander due to erosion.

River cliff Because of the gentle slope, there is a lot of frictional drag and so therefore the river flows at this speed

Fastest flow Maximum depth of the channel. (Note the asymmetrical cross-profile)

Slowest flow There is little frictional drag from the bed and bank at this point and so the river can flow at this speed.

Can you match up the characteristic

s below?

Meanders

12

3

Floodplain

Deposits on the inner meander bend where there is low energy

Erosion on the outer bend where there is faster flow. It creates a river cliff

Slip-Off Slope

Direction of meander migrationDirection of meander migration

Can you match up the labels to the correct place on the diagram?

Cross section through a meander

Ox Bow Lake FormationCan you look at the diagram & explain the formation of ox-bow lakes?Can you look at the diagram & explain the formation of ox-bow lakes?

Ox Bow lake on Mississippi

More gentle sloping valley sides

Evidence of meanders

Land use

changes –

more urban areas.

Small floodplain begins to

develop on either side of the river,

The Lower Course of a River

Learning Objectives:To be able to describe and explain the formation of a flood plain, levees, delta and estuary.

Floodplains, Deltas and Levees.

The pictures below show a floodplain, a delta and levees. Using your prior knowledge of river processes come up with a theory to explain how they are formed. The key words underneath each picture will help.

deposition

Slow flow

alluvium (silt)

flood

flat

deposition

slow

sea/lake

load

channel

blocked

deposit

flood

large load

smaller load

Main Channel

Main Channel Levee

Sea/lake

Floodplain

Floodplain

Defintions

Flood plains • A flood plain is the wide, flat area of

land on either side of the river in its middle and lower course.

Levees • Levees are natural embankments of silt

along the banks of a river, which are often several metres higher than the flood plain.

1. Floodplains and leveés are formed by deposition in times of river flood.

2. The river’s load is composed of different sized particles.

3. When a river floods, the river water overflows the banks of the river and immediately slows down due to friction.

4. This drops the larger particles first, building up a raised river bank called a LEVEÉ.

5. The sands, silts and clays are similarly sorted with the sands being deposited next, then the silts and finally the lightest clays. This builds up the floodplain.

Floodplain & Levee formation

Levee formation

This is a cross section of a floodplain.

Can you draw a simple sketch of the diagram and the labels below and then annotate it to explain how it is formed?

leveés clays and siltssands

How a floodplain is formed

Delta FormationDeltas form at the mouths of many of the world’s larger rivers, e.g the Nile (Egypt), the Ganges (Bangladesh), the Mississippi (USA).

A delta is a flat area of sand and silt built into the sea. It is formed by deposition.

1. When a river enters a sea or lake carrying large volumes of fine material, the velocity slows and causes the load to be deposited in layers.

2. Over time, the deposited material blocks channels and forms small islands separated by river channels called distributaries.

EstuariesThere are no large deltas around the coasts of the UK, instead the tidal mouth of a UK river is typically characterised with an estuary. Estuaries are wide river valleys flooded daily by the tide.

At low tide, large expanses of mud and sandflats are exposed which are mostly composed of material deposited by the river, e.g Thames, Humber, Severn.

Thames Estuary