Rivers: a revision session

River facts River 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 course A 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.waterfalls Middle: slip off slopes, river cliffs, meanders and asymmetric cross section Lower: flood plains, levees, ox bow lakes and deltasflood plainsox bow lakes

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

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