1. Channelisation

4. Channelisation:

5. Channelisation:
A deliberate attempt to alter the natural geometry of a water
course. It is an example of hard engineering.

6. Channelisation:
A deliberate attempt to alter the natural geometry of a water
course. It is an example of hard engineering.
The reasons for using channelisation can include:

7. Channelisation:
A deliberate attempt to alter the natural geometry of a water
course. It is an example of hard engineering.
The reasons for using channelisation can include:
• Increasing the capacity of a channel to prevent flooding.

8. Channelisation:
A deliberate attempt to alter the natural geometry of a water
course. It is an example of hard engineering.
The reasons for using channelisation can include:
• Increasing the capacity of a channel to prevent flooding.
• Providing a straighter and deeper channel for navigation.

9. Channelisation:
A deliberate attempt to alter the natural geometry of a water
course. It is an example of hard engineering.
The reasons for using channelisation can include:
• Increasing the capacity of a channel to prevent flooding.
• Providing a straighter and deeper channel for navigation.
• Preventing bed or bank erosion.

10. Channelisation:
A deliberate attempt to alter the natural geometry of a water
course. It is an example of hard engineering.
The reasons for using channelisation can include:
• Increasing the capacity of a channel to prevent flooding.
• Providing a straighter and deeper channel for navigation.
• Preventing bed or bank erosion.
• Reclamation of wetland by lowering the water table.

11. Channelisation:
A deliberate attempt to alter the natural geometry of a water
course. It is an example of hard engineering.
The reasons for using channelisation can include:
• Increasing the capacity of a channel to prevent flooding.
• Providing a straighter and deeper channel for navigation.
• Preventing bed or bank erosion.
• Reclamation of wetland by lowering the water table.
• Straightening rivers to make farm land more manageable, or to
allow bridges or highways to be built more easily.

13. 1. Resectioning or enlarging

14. 1. Resectioning or enlarging
2. Realignment or straightening

15. 1. Resectioning or enlarging
2. Realignment or straightening
3. Bank protection

16. 1. Resectioning or enlarging
2. Realignment or straightening
3. Bank protection
4. Lined channels

17. 1. Resectioning or enlarging
2. Realignment or straightening
3. Bank protection
4. Lined channels
5. Containment

18. 1. Resectioning or enlarging
2. Realignment or straightening
3. Bank protection
4. Lined channels
5. Containment
6. Vegetation Clearance

19. 1. Resectioning or enlarging
2. Realignment or straightening
3. Bank protection
4. Lined channels
5. Containment
6. Vegetation Clearance
7. Dredging

21. 1. Resectioning or enlarging

22. 1. Resectioning or enlarging
• Involves enlarging the cross-section of the channel.

23. 1. Resectioning or enlarging
• Involves enlarging the cross-section of the channel.
• The channel is deepened and / or widened to increase its
hydraulic efficiency, and to allow a larger discharge to be
contained within the channel.

24. 1. Resectioning or enlarging
• Involves enlarging the cross-section of the channel.
• The channel is deepened and / or widened to increase its
hydraulic efficiency, and to allow a larger discharge to be
contained within the channel.
• Can also be used to lower the water table on the floodplain,
therefore allowing wetlands to be reclaimed for agriculture.

27. 2. Realignment or straightening

28. 2. Realignment or straightening
• A meandering river can be straightened by means of artificial
cut-offs.

29. 2. Realignment or straightening
• A meandering river can be straightened by means of artificial
cut-offs.
• The aim is to increase the long profile gradient so that there is
an increase in velocity and flood waters can be removed more
quickly.

30. 2. Realignment or straightening
• A meandering river can be straightened by means of artificial
cut-offs.
• The aim is to increase the long profile gradient so that there is
an increase in velocity and flood waters can be removed more
quickly.
• Can also have an economic impact on river transport.

33. 3. Bank Protection

34. 3. Bank Protection
• Erosion of banks and meander migration causes loss of land
and may undermine structures such as building and bridges.

35. 3. Bank Protection
• Erosion of banks and meander migration causes loss of land
and may undermine structures such as building and bridges.
• Concrete blocks.

36. 3. Bank Protection
• Erosion of banks and meander migration causes loss of land
and may undermine structures such as building and bridges.
• Concrete blocks.
• Steel revetments.

37. 3. Bank Protection
• Erosion of banks and meander migration causes loss of land
and may undermine structures such as building and bridges.
• Concrete blocks.
• Steel revetments.
• Gabion boxes.

38. 3. Bank Protection
• Erosion of banks and meander migration causes loss of land
and may undermine structures such as building and bridges.
• Concrete blocks.
• Steel revetments.
• Gabion boxes.
• Wing dykes (groynes).

41. 4. Lined channels

42. 4. Lined channels
• Resectioned lengths of river are often lined with concrete to
improve channel efficiency.

43. 4. Lined channels
• Resectioned lengths of river are often lined with concrete to
improve channel efficiency.
• There is a reduction in the energy lost through friction so flow
velocity increases.

44. 4. Lined channels
• Resectioned lengths of river are often lined with concrete to
improve channel efficiency.
• There is a reduction in the energy lost through friction so flow
velocity increases.
• Flood risk is decreased as water is moved away quicker.

45. 4. Lined channels
• Resectioned lengths of river are often lined with concrete to
improve channel efficiency.
• There is a reduction in the energy lost through friction so flow
velocity increases.
• Flood risk is decreased as water is moved away quicker.
• Lined channels are often used in urban areas where access for
maintenance is limited or other forms of management are not
possible.

47. 5. Containment

48. 5. Containment
• An extreme form of channelisation.

49. 5. Containment
• An extreme form of channelisation.
• The channel is contained within concrete arches or pipes.

50. 5. Containment
• An extreme form of channelisation.
• The channel is contained within concrete arches or pipes.
• Used where rivers flow under roads or built-up areas.

51. 5. Containment
• An extreme form of channelisation.
• The channel is contained within concrete arches or pipes.
• Used where rivers flow under roads or built-up areas.
• Can be difficult to maintain because of access problems.

52. 5. Containment
• An extreme form of channelisation.
• The channel is contained within concrete arches or pipes.
• Used where rivers flow under roads or built-up areas.
• Can be difficult to maintain because of access problems.
• They have a flood design level, above which they may cause
ponding.

56. 6. Vegetation Clearance

57. 6. Vegetation Clearance
• A smooth, regular channel can carry three times the discharge
of a channel of similar size and gradient, which has its banks
covered with extensive weeds, reeds and other plants.

58. 6. Vegetation Clearance
• A smooth, regular channel can carry three times the discharge
of a channel of similar size and gradient, which has its banks
covered with extensive weeds, reeds and other plants.
• Plants reduce the size of the channel and aid silt deposition.

59. 6. Vegetation Clearance
• A smooth, regular channel can carry three times the discharge
of a channel of similar size and gradient, which has its banks
covered with extensive weeds, reeds and other plants.
• Plants reduce the size of the channel and aid silt deposition.
• Seasonal cutting can be ecologically beneficial.

60. 6. Vegetation Clearance
• A smooth, regular channel can carry three times the discharge
of a channel of similar size and gradient, which has its banks
covered with extensive weeds, reeds and other plants.
• Plants reduce the size of the channel and aid silt deposition.
• Seasonal cutting can be ecologically beneficial.
• Removal of vegetation is normally achieved with great
ecological damage.

62. 7. Dredging

63. 7. Dredging
• Involves the removal of sediment from the channel to enlarge
its capacity.

64. 7. Dredging
• Involves the removal of sediment from the channel to enlarge
its capacity.
• The dredged material can be removed from the channel or just
loosened and the channel flow utilised to remove it.