rivers

• Long profile of a river


  Gradient of the river from source to mouth
• Cross profile of a river

  Changes from narrow V-shape valleys to wider riverbed
• Types of river erosion

  • Vertical erosion
  • Lateral erosion
  • Hydraulic action
  • Abrasion
  • Attrition
  • Bank dissolution
• Types of river transportation

  • saltation
  • traction
  • Suspension
  • solution
• Landforms formed by river erosion

  • Interlocking spurs
  • Waterfalls
  • Gorges
  • Meanders
  • Oxbow lakes
• Floodplains


  Wide, flat areas to either side of a river with fertile soils
• Levees


  Raised riverbeds mainly found on the lower course of a river
• Estuaries


  Occur when large amounts of material are deposited, can form mud flats or salt flats
• Factors affecting flood risk

  • Physical factors: precipitation, rock type, slope steepness, precipitation frequency
  • Human factors: building on floodplains, paving over gardens, deforestation, farming practices
• Flood hydrograph


  Plot of river discharge after a storm
• Discharge


  Measured in meters cubed per second
• Lag time


  Time from peak rainfall to peak river discharge
• Base flow


  Normal flow of the river
• Flashy/storm hydrograph


  • Small river basin, prolonged rainfall, impermeable rocks, steep sided valley, high urban land use, little vegetation, saturated soil
• Slow/flat hydrograph


  • Large river basin, longer lag time, permeable rocks, gentle sloping valley, vegetation/forest
• Hard engineering techniques for rivers

  • Dams and reservoirs
  • Flood relief channels
  • River straightening
  • Embankments
• Soft engineering techniques for rivers

  • Flood warning systems
  • Floodplain zoning
  • Tree planting
  • River restoration