Geography: Rivers

• Confluence


  The point where two rivers join
• Drainage Basin


  The area drained by a river and its tributaries
• Tributary


  A river or stream flowing into a larger river or lake
• Floodplain


  Flatland across which a river usually flows
• Watershed


  The boundary between two river basins
• Load


  All the material carried by a river
• Deposition


  The process which occurs on the inside of a meander
• Interlocking Spurs


  Projecting areas of high ground around which a river flows
• Potholes


  Holes in the bedrock eroded by swirling stones
• Oxbow


  A lake formed when a river bend is cut off
• Estuary


  A wide river mouth, called a firth in Scotland
• 1. shaped valley


  The profile of a valley eroded by a river
• Braiding


  Where a river divides into two or more interconnecting channels
• Meander


  A pronounced bend on a river
• Levées


  Natural embankments on river banks deposited when the river floods
• Source


  The point at which a river begins
• Alluvium


  Sediment deposited by a river, usually on the floodplain
• Delta


  A large fan-shaped area of deposits found at the mouth of a river
• Types of Erosion Process

  • Solution
  • Hydraulic action
  • Attrition
  • Abrasion
• Types of Transport


  • Solution
  • Suspension
  • Saltation
  • Traction
• The less resistant rock is eroded more quickly
• 1. shaped valleys and interlocking spurs


  • Rivers cut down and widen their valleys
  • Rivers begin high in the mountains and flow downhill eroding the landscape
  • The river cuts down into the landscape using hydraulic action, corrosion and abrasion
  • As the river erodes downwards the sides are weathered which steepens the sides
  • Rocks that have fallen into the river help erosion and lead to further erosion
  • The river transports rocks and the channel becomes wider and deeper creating a U-shaped valley
• Floodplain and levee


  • Floodplains form from erosion and deposition
  • Levees can form in the lower course of a river where there is an increase of water
  • Sediment that has been eroded upstream is transported downstream
  • When the river floods, the sediment is spread across the floodplain
  • When floods recede, the river loses energy and the largest material is deposited on the sides then smaller material further away
  • After floods, the sediment builds up, increasing the height of the river banks narrowing the channel
• Meanders, pools and riffles, helicoidal flow

  • In a straight river, pools and riffles develop as water flows around obstructions
  • Pools have deeper water and greater erosion, riffles are shallow areas created by deposition
  • Once pools and riffles have developed, the river flows from side to side in a winding course
  • Helicoidal flow is a corkscrew-like flow of water that moves material from one bank and deposits it on the inside of the next bend
  • Fast moving water on the outside of the bend has more energy and erodes through hydraulic action, corrosion and abrasion
  • Water moves slowly on the inside bend and deposits its load, creating a sloping river beach
  • Erosion on the outer bank and deposition on the inner bank will form meanders, which will migrate downstream over time
• Flood risk


  How often the risk of flooding will take place
• Possible flood impacts


  • Inundation of the ground
  • Flooding homes or shops
• Causes of flooding


  • Increased rainfall
  • Saturated land from previous rainfall
  • Deforestation
  • Lack of dredging (rivers clogged with sediment)
• The two rivers that flooded in the Somerset Levels were the River Tone and Parrett
• Flooding had taken place to the east of Taunton, with large parts of the town suffering from flooding
• Patches of flooding occurred to the south-east of Bridgwater and to the east of Taunton, but not at the coast