River Channel Management Strategies


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A discussion on various river channel management strategies and their advantages and disadvantages.

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  • Great presentation!! I am actually writing my dissertation on River Channelisation and the positives and negatives of it.I was wondering if you could send me an email to (oliverwilks@live.co.uk) with any papers or journals that you have come across. It would be a massive help! Thank you !!
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  • why did you disable saving it? It makes it a real pain to use for revision!
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  • gd presentation but needs detailed examples
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River Channel Management Strategies

  1. 1. River Channel Management Strategies
  2. 2. Re-alignment
  3. 3. Re-alignment <ul><li>Straightening of the river channel </li></ul><ul><li>Removes meanders and reduces the length of the river channel in order to increase the speed of the river </li></ul>
  4. 4. Re-alignment <ul><li>Faster flow of river allows water to flow away more quickly and wash away sediments which have accumulated on the river bed, minimising flooding </li></ul><ul><li>Also deepens the channel, allowing it to hold more water, reducing the occurrence of floods </li></ul>
  5. 5. Re-sectioning
  6. 6. Re-sectioning <ul><li>Widening and deepening of the river channel </li></ul><ul><li>This increases the channel’s ability to hold water, thus decreasing the chances of floods </li></ul><ul><li>Re-sectioning increases the amount of surface runoff from the surrounding areas into the river, because more surface runoff can now enter the river without causing it to flood </li></ul>
  7. 7. <ul><li>River bed and banks may be smoothened by replacing the soil of the river banks and bed with cement and granite </li></ul><ul><li>There is less friction between the water and river bed and banks </li></ul><ul><li>Speed of river will increase and allow water to flow away from the area more quickly </li></ul>Re-sectioning
  8. 8. Bank Protection
  9. 9. Bank protection <ul><li>Prevent floods from occurring and reduce soil erosion along river banks </li></ul><ul><li>Artificial levees or dykes are walls of sand, stone or concrete built along rivers </li></ul><ul><li>These increase the capacity of the river to hold water, reducing chances of flooding. </li></ul>
  10. 10. Bank protection <ul><li>Concrete structures like gabions and revetments are built along a river channel to divert the flow of water from the river banks to the centre of the channel </li></ul><ul><li>Protects the river banks from being eroded by the force of running water, reducing the amount of sediments that enter the river </li></ul><ul><li>This increases the capacity of the river to hold water, reducing the frequency of flooding </li></ul>
  11. 11. Planting Vegetation
  12. 12. Planting vegetation <ul><li>Protects river banks against erosion as roots of trees and other plants hold the soil together firmly </li></ul><ul><li>Also slows down the rate of surface runoff, preventing large amounts of water from entering the river at any one time </li></ul><ul><li>Reduces the amount of eroded sediment being transported into the river </li></ul>
  13. 13. How effective are these strategies?
  14. 14. How effective are these strategies? <ul><li>Re-alignment and re-sectioning are effective long-term measures. However, a lot of resources and manpower are required to carry them out </li></ul><ul><li>Re-alignment can cause increased erosion of river channel because of the increase in the speed of flow </li></ul><ul><li>Widening and deepening the river channel in re-sectioning increases the wetted perimeter, leading to slower river speed and increased deposition, which will decrease the size of the channel over time </li></ul>
  15. 15. How effective are these strategies? <ul><li>Bank protection may protect against flooding in the short term </li></ul><ul><li>However, the cost of building and maintenance of these structures is quite high </li></ul><ul><li>They interfere with natural processes and are aesthetically unappealing </li></ul><ul><li>Floodwaters can still break through at weaker sections, causing flooding in surrounding areas </li></ul>
  16. 16. How effective are these strategies? <ul><li>Planting of vegetation takes time for the plants to grow and mature before benefits can be seen </li></ul><ul><li>Not effective in urban or in polluted areas </li></ul><ul><li>Woody debris from plants can accumulate on river banks and bed, increasing friction and slowing down speed of flow </li></ul>
  17. 17. How effective are these strategies? <ul><li>How might river channelisation affect other parts of the river? </li></ul>
  18. 18. Flooding downstream <ul><li>Channelisation upstream leads to higher volume of water flowing downstream. Channel in the area downstream might not be able to contain the increased flow of water and overflows, resulting in flooding </li></ul><ul><li>Floods in one part of the river’s course are managed, but they can still occur in another part of the river </li></ul>
  19. 19. Accumulation of sediments <ul><li>With channelisation, river now has higher speed and more energy to carry sediments downstream </li></ul><ul><li>Sediments which are normally deposited on the river bed get washed downstream or into the sea or ocean </li></ul>
  20. 21. Accumulation of sediments <ul><li>Increased sediments in the sea result in less sunlight reaching the seabed, affecting the growth of marine life like seagrasses and coral reefs </li></ul>
  21. 22. Accumulation of sediments <ul><li>Construction of dykes, revetments and gabions causes sediments to accumulate behind these structures. </li></ul><ul><li>As sediments build up, the river channel becomes shallower. </li></ul><ul><li>Heavy rains may cause the water in the river to overflow and cause flooding. </li></ul>
  22. 23. Loss of marine life and wetlands <ul><li>Channelisation may destroy ecosystems. E.g. Re-alignment and covering the river banks and bed with cement will destroy the habitat of many species. </li></ul><ul><li>Channelisation may also lead to the disappearance of wetlands </li></ul>