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THE MIDDLE COURSE

THE MIDDLE COURSE In the middle course, the river is deeper as a result of being joined by a number of tributaries. Less water is in contact with the river’s bed and banks, which means there is less friction . Less friction means the river has more power to erode .

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THE MIDDLE COURSE

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  1. THE MIDDLE COURSE In the middle course, the river is deeper as a result of being joined by a number of tributaries. Less water is in contact with the river’s bed and banks, which means there is less friction. Less friction means the river has more power to erode. Erosion and transportation are the main processes operating in the middle course of a river. The valley is flatter with more gentle slopes. As a result, the direction of erosion is lateral (sideways). Lateral erosion makes the river wider.

  2. Meanders When rivers flow over flatter land they develop large bends called meanders

  3. KEY WORDS • Meander - a bend in a river. • River Cliff - a small cliff formed on the outside of a meander bend due to erosion. • Slip off Slope- a small river beach of built up sediment found on the inside of a meander bend due to deposition.

  4. Meander = a bend in a river

  5. Formation of meanders • On the outside of the bend, the current flows faster. This means it has more energy. • On the inside of the bend the water flows slower.

  6. Formation of meanders • On the outside of the bend, the current flows faster. This means it has more energy. • On the inside of the bend the water flows slower therefore it has less energy.

  7. SLIP OFF SLOPE • On the inside of the bend, the current flows slower and has less energy. The river therefore doesn’t have enough energy to carry its load. It drops the material it is carrying. Over time this creates a river beach technically known as a slip off slope

  8. RIVER CLIFF • On the outsideof the bend, the current flows quicklyand has more energy. The river uses its energy and load to erode the outside bed and banks by corrasion, corrosion and hydraulic action

  9. As the river erodes the outside of the bend and deposits material on the inside of a bend the channel will be deeper on the outside of a bend. This means it can carry more water and therefore it has more energy to transport material. Deep channel, large amount of water Material will be deposited.here. The channel will be shallow with less energy.

  10. A= River cliff B= Slip off slope B A

  11. MEANDERS SUMMARY • 1. The river flows fastest on the outside of a bend. The fastest current has a lot of energy to transport material. This material will erode the outside river bank through corrasionand the water will erode the bank through hydraulic action. The bank will be undercut and will collapse to leave a small river cliff. • 2. The river will shift sediment across the channel to the inside bank. Because there is less water at this point and it is slower moving, it has less energy to carry the sediment. The river deposits its load at the inside bank to form a slip off slope (a small river beach made up of sediment).

  12. As you can see from the above cross section, the river channel is much deeper at the outside of the meander bend due to continued erosion via hydraulic action and corrasion. On the inside of the bend where the river loses energy it drops its load and therefore the channel on the inner bend is much shallower.

  13. Summary • The valley shape in the middle course is U shaped • The inside of a meander bend has slower moving water • Deposition occurs on the inside of a meander bend foring a river beach (slip off slope) • The river has faster flow and more energy to transport material on the outside of a meander bend. It uses its energy and load to further erode the outside of the bend.

  14. Summary: The Middle Course • Erosion and Transportation are the main processes operating in the middle course of a river. • The direction of erosion is lateral. • Valleys are wider and flatter with more gentle slopes. • Meanders are bends in a river. • On the outside of the bend, the current flows faster, eroding the river bank to form a river cliff. • On the inside of the bend the current flows slower, allowing material carried by the river (its load) to be deposited – this creates a slip-off slope.

  15. Answers 1.) The valley shape in the middle course is U shaped 2.) The outside of a meander bend has faster moving water 3.)Erosion takes place on the outside bend undercutting the river bank forming a river cliff 4.)The inside of a meander bend has slower moving water 5.) Deposition occurs on the inside of the river bend 6.) Deposition forms a slip off slope

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