Rivers CSEC Geography

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Rivers CSEC Geography

  1. 1. Natural Systems RIVERS rm accounts ed ram@2013 rights reserved
  2. 2. Rivers • Definition – The natural flow of water from areas of highland towards low-lying areas a long a definite course (water course); and emptying itself in – – – – – The Sea Another river (tributary) A Lake A Swamp A Swallow Hole (reemerge as springs) rm accounts ed ram@2013 rights reserved
  3. 3. Some of the main features Source – The start of a river’s course Mouth – The point where a river flows into the sea Channel - the area along which the river flows • Tributary – a small river which flow into a larger one • Confluence – the point where a tributary joins the main river • Meander - a bend in the river rm accounts ed ram@2013 rights reserved
  4. 4. Stream Ordering Streams are ordered from the number 1 onward i.e. there are: – 1st order streams (the main river) – 2nd order streams (a tributary which feeds the main river) – 3rd order streams (a tributary which feeds another tributary which in turn feeds the main river) rm accounts ed ram@2013 rights reserved
  5. 5. Dendritic drainage pattern rm accounts ed ram@2013 rights reserved
  6. 6. The drainage pattern is • the pattern created by a river and its tributaries as seen from above. • the pattern is based on a number of factors: – The type and structure of the underlying rock – The shape of the land mass – The topography (layout of the land) rm accounts ed ram@2013 rights reserved
  7. 7. Types of drainage patterns • There are three types of drainage patterns : – Radial • (like the spokes of a bicycle wheel) – Trellised • (like the rectangular pattern created in block work) – Dendritic • (like the veins of a leaf) rm accounts ed ram@2013 rights reserved
  8. 8. RIVERS RIVER PROCESSES rm accounts ed ram@2013 rights reserved
  9. 9. Energy and Friction • The type of work a river performs over time depends on – the size and shape of its channel, – the volume of water it carries, as well as – the land surface over which it flows. • These factors determine the river’s speed (friction factor) and its power (energy factor). rm accounts ed ram@2013 rights reserved
  10. 10. Rivers • ERODE – (wear away the earth’s surface due to its rapid speed and steep channel) • TRANSPORT – (remove eroded earth material due to loss of speed as channel widens and gradient decreases) • DEPOSIT – (build up with eroded material due to its very slow speed and its relatively flat and wide channel) rm accounts ed ram@2013 rights reserved
  11. 11. River Erosion involves… • Corrosion (the water dissolves and removes soluble material in its path) • Abrasion (the water scours the bed and sides of its channel with its load) • Corrasion ( [see abrasion] the water uses the load to mechanically gouge of areas of the channel • Hydraulic Action (the force of the water dislodges material from the channel) • Attrition (the material in load bumps into each other an disintegrate) rm accounts ed ram@2013 rights reserved )
  12. 12. River Transportation involves… • Suspension (the lightest materials float along in the water’s currents) • Traction ( the heaviest materials bounce or roll along by the force of the water • Saltation ( some of the material hops and floats as the water moves downward • Solution (the dissolved minerals are carried along in the water itself) rm accounts ed ram@2013 rights reserved ) )
  13. 13. Deposition is a result of… • Rivers drop off their load when – Gradient or slope of the river bed decreases – The channel widens or becomes shallow – It enters an arid region and loses discharge and volume – It reaches a lake or sea, slowing it down rm accounts ed ram@2013 rights reserved
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  15. 15. RIVERS The valley stages rm accounts ed ram@2013 rights reserved
  16. 16. There are three life stages • The Youthful stage (Torrent, Upper) • The Mature stage (Middle) • The Old Age stage (Lower) rm accounts ed ram@2013 rights reserved
  17. 17. The life stages rm accounts ed ram@2013 rights reserved
  18. 18. Characteristics of the upper stage – Gradient averages 1 in 10 – Vertical corrasion is dominant – Valley sides are steep with a narrow V-shaped cross section – The river flows around spurs or interlocking spurs rm accounts ed ram@2013 rights reserved
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  20. 20. Erosional features • Potholes • Plunge pools (explain how each is formed) (circular depressions on the river bed) (a large (deep) depression at the foot of a waterfall) • Waterfalls (fast moving vertical flow of water from great height) • Rapids (a series of short, fast falls) • Gorges (steep sided, deep, narrow valleys) • rm accounts ed ram@2013 rights reserved
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  22. 22. Characteristics of the middle stage – Gradient is not as steep as the Youthful stage – lateral erosion is dominant – Valley sides are less steep with an open V-shaped (closer to a U) cross section – The river flows appear to meander across the channel as the interlocking spurs are being cut away. rm accounts ed ram@2013 rights reserved
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  24. 24. Characteristics of the old age stage – Gradient is rather low – deposition is dominant – Valley has a flat bedded U shaped (like a box) cross section creating a wide flood plain. – The river flows slowly as meanders are more pronounced. – Silting and emerging vegetation hampers its flow in some areas. rm accounts ed ram@2013 rights reserved
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  26. 26. Depositional features • Meanders (explain how each is formed) (a loop or definite bend in the river) • Ox-bow lake (a crescent-shaped lake at the cut off of a meander’s neck) • Deltas (a flat piece of land built up by deposits at the river’s mouth) • Flood plains (a low-lying plain resulting from continuous overflowing of the river’s banks) • Levees (natural embankments built up by the river on the banks of the channel) • rm accounts ed ram@2013 rights reserved
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  28. 28. Spot the rivers features rm accounts ed ram@2013 rights reserved

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