BANK PROTECTION AND WADI TRAINING

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BANK PROTECTION AND WADI TRAINING

• Lesson 2

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Bank protection and Wadi training

• High flow velocities during spates often erode
  Wadi banks
• meander patterns to develop and migrate
  downstream
• Wadi beds can be significantly lowered during the
  passage of large floods
• traditional intakes to be left stranded

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• Providing engineered structures to control bed
  levels
• Farmers give bank protection work a high priority
  
• training and back protection works that cause
  damage elsewhere
• River training and bank protection approached in
  a holistic manner

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blocks Vs. crated boulders

• The subject has been well debated.
• General experience, which has served successfully
  for over 100 years, is to use crated boulders in
  alluvium deposits for launching aprons.
• The size of crate is determined on the basis of
  water velocity to prevent it being swept and
  lifted away.

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• The basic principle of the launching apron is
  best described as the one of a carpet which takes
  the shape of the scoured bed.
• The bottom of the apron is normally placed at
  LWL.
• It is not possible to lay the apron below knee
  deep water because of difficult manual working.
• In such cases, it is best to fill the area, if
  necessary by using suction dredgers

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• Crated boulders launch smoothly and being
  flexible, easily take the shape of the scoured
  beds and are not lost as in case of concrete
  blocks
• For pitching guide bunds, slopes also, boulders
  in the form of grids are used.

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gabion apron

• Require minimal excavation and grade work.
• Generally the gabion apron is placed directly on
  the ground utilizing a geotextile filter fabric
  between the gabion apron soil interface to
  prevent and leaching of soils from underneath the
  apron.
• Gabions or reno mattresses may also be connected
  together filled and then placed into the water
  with a sling arrangement. This method is
  frequently used for building scour-resisting mats
  around bridge piers etc

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