Rivers

• Stores


  • Sea
  • Glaciers
  • Lakes
• Processes of river erosion


  • Corrosion
  • Hydraulic action
  • Attrition
• Ways a river transports its load


  • Solution
  • Suspension
  • Saltation
  • Traction
• Moving downstream


  • Decrease in river gradient
  • Increase in water volume
  • Increase in sediment carried
• Deltas occur where a river splits into a series of distributaries
• Catchment area


  The area within the drainage basin
• Watershed


  The edge of a highland surrounding a drainage basin. It marks the boundary between two drainage basins
• Source


  The beginning or start of a river
• Confluence


  The point at which two rivers or streams join
• Tributary


  A stream or smaller river joins a larger stream or river
• Mouth


  Where the river ends, usually when entering the sea
• River Processes


  • Erosion
  • Transportation
  • Deposition
• Erosion


  The wearing away of surfaces
• Types of Erosion


  • Vertical erosion: dominant in the upper course of rivers. It increases the river's depth and valley as the river erodes downwards.
  • Lateral erosion: dominant in the middle and lower course of rivers. It increases the width of the river and valley as it erodes sideways.
• Erosion Processes


  • Attrition: large particles such as boulders collide and break into smaller pieces.
  • Hydraulic action: flowing water that hits against the riverbanks and beds.
  • Abrasion: smaller particles rub against the riverbanks and bed like sandpaper.
  • Solution: acid in rivers dissolves rocks; it occurs at any part of the river
• Transportation Processes


  • Traction: rolling stones along the bed
  • Saltation: small particles bounce along the bed in a leapfrog motion
  • Suspension: silt and clay-sized are carried within the water flow
  • Solution: minerals dissolve in the water
• Deposition


  When a river lacks the energy to carry its load, it deposits the heaviest particles
• Large boulders are deposited at the top, and very small particles are deposited at the end, resulting in sorting
• River Profiles


  • Long profile
  • Cross Profile
• River Landforms and their Formation


  • Water Fall and Gorges
  • V-shaped valley
  • Interlocking Spurs
  • Meanders
  • Oxbow Lake
  • Floodplains and Levees
• Causes of flooding


  • No vegetation
  • Deforestation
  • Urbanization
  • Poor drainage
  • Steep slopes
  • Rock type (impermeable rocks do not absorb water)
  • Wet soil (over saturation)
• Impacts of Flooding


  • People can be killed
  • Homes destroyed
  • Spread of waterborne diseases
  • Shortage of clean water and food
  • Infrastructure damaged
  • Businesses destroyed
• Opportunities from Flooding


  • Water supply (drinking, washing)
  • Fishing industry
  • Transportation for trading
  • Tourism
  • Fertile soil
  • Powerplants (dams)
  • Sports/recreation
• V-shaped valley


  A river's discharge is low in the upper course, so the river can only erode downwards(vertical erosion). The valley's sides are broken through weathering. The weathered materials are transported via gravity and rainfall towards the river channel. this steepens the valleys sides. The valley shapes are narrow and steep
• Meanders


  Bends or curves in a river channel. Formed when a river erodes its outer banks more quickly than its inner banks, causing the channel to bend and twist over time.
• Oxbow Lake


  Formed when a meander becomes so curved that it is cut off from the main river channel, creating a crescent-shaped lake. This process is called river avulsion.
• Floodplains and Levees


  Floodplain: the flat area of land adjacent to a river that is periodically flooded. Levee: a natural or artificial bank built along the edge of a river to prevent flooding.
• Interlocking Spurs


  Formed when tributaries join the main river channel, creating triangular-shaped areas of land that extend into the valley. Often covered in vegetation and provide important habitat for wildlife.
• Waterfalls and gorges usually form at the upper stages of a river. A band of hard rock overlies soft rock and falling water erodes the soft rock, creating a plungepool. The soft rock is undercut by erosional processes such as hydraulic action and abrasion. In the plunge pool, the water debris swirls around and erodes further deepening it, creating an overhang. The hard rock overhang above the plunge pool collapses as it can no longer be supported. Erosional processes cause the waterfall to move upstream creating a gorge