RIVERS

• River


  A body of water flowing in a channel downslope under the influence of gravity
• As the river flows, it shapes the landscape
• River courses


  • Upper course
  • Middle course
  • Lower course
• Upper course


  • Steep slope
  • Fast-flowing river
  • Narrow channel
  • Low volume of water
• Middle course


  • Gentle slope
  • Slower-flowing river
  • Meander channel
  • Larger volume of water
• Lower course


  • Almost flat slope
  • Slower-moving river
  • Wide, flat valley
  • Wide, shallower channel
• Most active processes in river courses

  • Erosion (vertical)
  • Erosion (lateral)
  • Deposition
• River landscape features


  • V-shaped valleys
  • Meanders
  • Levees
  • Interlocking spurs
  • Waterfalls
  • Oxbow lakes
  • Deltas
  • Floodplains
• River basin


  The area drained by a river and its tributaries
• Watershed


  The high ground that separates two river basins
• River course


  The journey the river takes to the sea
• River source


  Where a river starts, high up in the mountains
• Interlocking spurs


  Crossing points of hard rock that the river cannot erode through
• Waterfalls


  Vertical drops in the upper course of a river formed by vertical erosion
• Meanders


  Bends that form in the middle course of a river due to greater lateral erosion
• Levees


  Ridges of sediment deposited on the banks of the river in the lower course
• Estuary


  The part of the river affected by tides, where a delta may be deposited
• When water falls on land, it drains into rivers, which carry it to lakes and seas
• The features in an area are called the landforms of the area. As rivers drain the land, they form different features.
• River processes


  • Erosion
  • Transportation
  • Deposition
• Erosion


  The wearing away of the bed and banks of a river
• Erosion processes


  • Hydraulic action
  • Attrition
  • Abrasion
  • Solution
• Transportation processes


  • Rolling
  • Bouncing
  • Solution
  • Suspension
• Deposition


  When a river drops its bedload
• Reasons for deposition


  • Decrease in speed
  • Decrease in volume
  • Increase in bedload
• 1. shaped valley


  • Steep-sided river valley with a narrow floor, formed by vertical erosion
• Interlocking spurs


  • Areas of high ground that jut out on either side of the river, formed by erosion around hard rock
• Waterfall


  A vertical fall in the upper course of a river, formed where hard rock meets soft rock
• Meander


  A large bend in a river channel, formed by lateral erosion and deposition in the middle course
• Oxbow lake


  A lake in the shape of a horseshoe, formed when a meander is cut off
• Floodplain


  A wide area of flat land on either side of a river, formed by deposition during floods
• Lateral erosion


  The process where the river erodes the neck of land between the ends of the meander
• Meander


  A winding curve in the river
• Formation of an oxbow lake

  1. River erodes straight through the narrow neck during a flood

  2. River no longer follows the meander loop

  3. River flows straight on

  4. Speed of the river decreases at the entrance to the old meander

  5. Deposition of sediment

  6. Both ends of the meander are sealed off

  7. Oxbow lake forms
• Oxbow lake formation


  • River Moy north of Ballina, Co. Mayo
  • Castletown River near Dundalk
• Floodplain


  • Wide area of flat land on either side of a river
  • Feature of deposition
  • Forms in the middle and lower course of a river
• Formation of a floodplain

  1. During periods of heavy rain, water flows over the river banks

  2. Lateral erosion creates a wide area of flat land

  3. When the river loses speed, it deposits its load

  4. Larger material is deposited near the riverbanks

  5. Finer alluvium is deposited further away

  6. Repeated flooding builds up the floodplain
• Floodplains


  • River Suir east of Limerick
  • Garfinny River, Dingle, Co. Kerry
• Levees


  • Long, narrow mounds or ridges of alluvium that run along the banks of a river
  • Features of deposition
  • Form in the lower course of a river
• Formation of levees


  1. During a flood, the river spreads out over the floodplain and loses speed

  2. This causes the river to deposit its load

  3. Larger, heavier sediment is deposited close to the riverbanks

  4. Finer alluvium is deposited further out

  5. Repeated flooding builds up the sediments to form levees