Rivers

• Drainage basin


  An area that is drained by a river and its tributaries
• Drainage basin


  • Source (where the river starts, usually in an upland area)
  • Tributaries (smaller rivers that flow into a larger one)
  • Watershed (imaginary lines separating two drainage basins)
  • Channel (main channel through which the water flows)
  • Confluence (point where two rivers meet)
  • Mouth (where the river ends and flows into a sea or lake)
• Hydrological cycle


  Also referred to as the water cycle, a closed circle where the amount of water on Earth is constantly recycled
• Stores in the hydrological cycle

  • Ice and snow
  • Intercepted water (stopped by trees or rooftops)
  • Lakes
  • Soil
  • Rocks
• Transfers in the hydrological cycle

  • Precipitation
  • Interception
  • Overland flow
  • Infiltration
  • Subsurface flow
  • Percolation
  • Groundwater flow
  • Evaporation
  • Evapotranspiration
• River bed


  The bottom of the river
• River banks


  The sides of the river
• River width


  The distance between the two banks
• River depth


  The distance from the water surface to the bed of the river
• River speed of flow


  How fast the water in the river is moving
• Wetted perimeter


  The part of the river that has contact with water
• River channel


  The route or parts through which the water flows
• River long profile


  • Shows changes in river gradient from source to mouth
  • Divided into upper, middle and lower course
  • Upper course has steep slope, middle course has gentler slope, lower course has flat floodplains
• River cross profile


  • Shows changes in river channel from one bank to the other
  • Upper course is shallow, narrow and has steep slopes
  • Middle course is deeper, wider and has gentler slopes
  • Lower course is very deep, wide and has flat floodplains
• Reasons for variation in river flow during the year

  • Variation in amount of precipitation
  • Variation in intensity of precipitation
  • Variation in temperature
  • Variation in evapotranspiration
  • Variation in ground saturation
  • Melting of glaciers, ice and snow
  • Extraction of water
• River erosional processes


  1. Hydraulic action

  2. Abrasion/Corrosion

  3. Attrition

  4. Solution/Corrosion
• Hydraulic action


  • when the river uses its force of flow as tools to erode
• Abrasion/Corrosion


  Smaller particles rub against the bed and the banks of a river, making the river wider and deeper
• Attrition


  Particles being transported in the river hit against each other hence breaking into smaller pieces
• Solution/Corrosion


  The river dissolves some types of rocks such as chalk and limestones
• Factors affecting rate of erosion

  • Load (size and shape)
  • Velocity and discharge
  • Gradient
  • Geology (rock type)
  • Acidity of water
  • Human impact
• River transportational processes


  1. Traction

  2. Solution

  3. Suspension

  4. Saltation
• Traction


  Large materials are rolled or pushed along the bed of the river
• Solution


  Material dissolved in the water and carried along
• Suspension


  Light materials are carried in the flow, suspended in the water
• Saltation


  Materials bounce along the riverbed, also called the leap frog method
• River depositional processes


  Occurs when the speed of flow reduces, the river is carrying too heavy a load, or the water is still
• Areas of deposition


  • Inner bend of a meander
  • Lower course around the mouth (forming deltas)
  • Levees
  • Floodplains