River Landforms

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  • Created by: vampette
  • Created on: 12-04-14 09:25
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  • River landforms
    • Meanders are large bends in rivers
      • They are formed when the current is faster on the outside of the bend because the river channel is deeper. So more erosion takes place on the outside of the bend, forming river cliffs.
      • The current is slower on the inside of the bend because the river channel is shallower. So eroded material is deposited on the inside of the bend, forming slip off slopes.
    • Waterfalls and gorges are found in the upper course of a river
      • Waterfalls form when a river flows over an area of hard rock followed by an area of softer rock. the softer rock is eroded more than the hard rock, creating a 'step' in the river.
        • As water goes over the step it erodes more and more of the softer rock. A steep drop is eventually created, called a waterfall.
          • The hard rock is eventually undercut by erosion. It becomes unsupported and collapses.
            • The collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rocks by abrasion, creating a deep plunge pool.
              • Over time, more undercutting causes more collapses and eventually the waterfall will retreat leaving behind a steep sided gorge.
    • Ox-bow lakes are formed from meanders
      • Erosions causes the outside bends to get closer until there's only a small bit of land left between the bends (called the neck).
        • The river breaks through this land, usually during a flood and the riverflows along the shortest course.
          • Deposition evedntually cuts off the meander forming an ox-bow lake.
    • Flood plains are flat areas of land that flood
      • The flood plain is the wide valley floor on either side of the river which occasionally gets flooded.
      • Meanders migrate across the flood plain, making it wider. The deposition that happens on the slip-off slopes of meanders also builds up the flood plain.
    • Levees are natural embankments
      • During a flood eroded material is deposited over the whole flood plain.
        • The heaviest material is deposited closest to the river channel, because it gets dropped first when the river slows down.
          • Over time, the deposited material builds up, creating levees along the edges of the channel.

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