River landforms (WJEC Eduqas GCSE Geography B): Revision Note

How this note links to the specification

The notes on this page cover part 2.2. 1 of the WJEC Eduqas GCSE B Geography.

2.2.1 How do people and processes contribute to the development of distinctive river landscapes in the UK?

• How fluvial processes, combined with weathering, mass movement and human activities create distinctive river landscapes in the UK.

• Coverage of landforms must include v-shaped valleys, waterfalls, gorges, meanders, ox-bow lakes, floodplains and estuaries. How human activity affects river landscapes to include creation of reservoirs, dredging and straightening of channels.

• How human activity affects river landscapes to include creation of reservoirs, dredging and straightening of channels

River landforms

• The changes in river channel characteristics, lead to changes in the river landscape

• The upland and lowland areas of rivers have distinctive landforms

Upland river landforms

• Upland river landforms include:

  • Waterfalls

  • Gorges

  • V-shaped valleys

  • Interlocking spurs

Waterfalls and gorges

• Waterfalls form where there is a drop in the riverbedfrom one level to another

• This drop is often due to changes in the hardness of rock, where hard rock overlies soft rock

• Hydraulic action and abrasion are the main erosional processes:

  • The soft rock erodes quicker, undercutting the hard rock and creating a plunge pool

  • This leads to the development of an overhang of hard rock which, eventually over time, collapses 

  • The overhang falls into the plunge pool increasing abrasion and making the plunge pool deeper

  • The process then begins again and the waterfall retreats upstream leaving a steep-sided gorge

V-shaped valleys 

• Vertical erosion is dominant in the upper course of the river

• This cuts down into the riverbedand deepens the river channel 

• Weathering and mass movement leads to material from the valley sides collapsing into the river, forming a steep v-shaped valley

Interlocking spurs

• In the upper course of the river, the channel starts to meander

• Erosion happens on the outside of the bend

• In the upland areas this forms interlocking spurs

Lowland river landforms

• Lowland river landforms include:

  • Meanders

  • Ox-bow lakes

  • Floodplains

  • Estuaries

Meanders 

• In lowland areas lateral erosion is dominant

• Meanders increase in size

• The fastest water flow (thalweg) is on the outside of the river bends, leading to erosion:

  • The erosion undercuts the riverbank, forming a river cliff

  • The river bank collapses and the edge of the meander moves further out

• The slowest flow is on the inside of the river bends, leading to deposition:

  • The deposits form a slip-off slope

• Deposition on one side and erosion on the other leads to the meander migrating across the valley

Ox-bow lakes

• With distance downstream the size of the meanders increase

• The erosion on outside bends can eventually lead to the formation of a meander neck

• At a time of flood, the river may cut through the neck of the meander, forming a straighter course for the water

• The flow of water at entry and exit from the meander will be slower, leading to deposition

• The meander becomes cut off from the main river channel, forming an ox-bow lake

Floodplains and levees

• Floodplains are flat expanses of land either side of the river

• The migration of meanders leads to the formation of the floodplain

• High discharge may cause the river to overflow the banks

• More of the water is in contact with land surface as the water spreads across the floodplain

• Increased friction reduces velocity and material is deposited across the floodplain gradually increasing the floodplain height

• The heaviest material is deposited first nearest to the river channel, forming natural embankments called levees

Estuaries

• An estuary is where the river meets the sea

  • Often a very wide, sheltered area

• This area of the river is tidal, which means when the tide goes out, the amount of water in the estuary is reduced

  • This exposes the mudflats at the side of the river channel

• The mudflats in the estuary are formed by deposition of the sediment carried by the river

  • As the river enters the sea, the velocity decreases, leading to deposition

  • The deposits of sediment build up over time

Human activity and river landscapes

• Human activity affects river landscapes in many ways, including:

  • Creation of reservoirs

  • Dredging

  • Straightening channels

Creation of dams and reservoirs

• Building dams across rivers creates reservoirs

• These are artificial stores of water used to increase water supply for:

  • Domestic use

  • Industry

  • Irrigation

• The dams can also be used to create electricity via hydropower

• The construction of dams and reservoirs

  • Controls the flow of the water downstream; this may result in lower or higher discharge

  • Creates a large water store which floods the river valley

Dredging

• Dredging involves removing sediment from the riverbed.

• This deepens the river and so increases its capacity

Channel straightening

• During channel straightening meanders on the river are removed

• This creates a shorter and straighter channel so that discharge moves through the channel more quickly