Rivers: a revision session

River factsRiver landforms are formed by erosion,

transportation and deposition

The main processes of river erosion are: abrasion, hydraulic action, attrition and solution. These operate best at times of flood.

A river’s load is transported by solution, suspension, saltation and traction

Parts of a river’s courseA river can be subdivided into its upper, middle

and lower course. Each part will have distinctive landforms and characteristics.

• Upper: potholes, V shaped valleys, waterfalls and interlocking spurs.

• Middle: slip off slopes, river cliffs, meanders and asymmetric cross section

• Lower: flood plains, levees, ox bow lakes and deltas

Flooding• Rivers will flood when the discharge or flow is

greater than the channel can cope with.

• Deforestation and the building of roads and houses on the flood plain increases surface runoff and reduces infiltration, increasing flood danger.

• Flooding can be reduced by building reservoirs, levees, and relief channels.

• Straightening the channel will increase the flow

Flood management

Two case studies :

• MEDC; Boscastle causes effects and ‘solutions

• LEDC; Mozambique, causes, effects and ‘solutions’.

Future

• There has been a move away from ‘hard’ solutions, e.g. the construction of levees to ‘soft’ solutions e.g. flood plain zoning.

• This is particularly true in LEDCs where they cannot afford the costs of large schemes