Case River Engineering Approach Wadi Labka Gabion Soil Diversion Spurs

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Case - River Engineering ApproachWadi Labka
Gabion/ Soil Diversion Spurs
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Wadi Labka (En-River), Eritrea
Wadi Labka Gorge
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Flow is divided in the riverbed
Three main command areas

• Scan of Map

Riverbed downstream of gorge
Flow
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Traditional method of diversion

• Combination of earthen bunds protected with
  acacia brushwood and natural vegetative bunds
  (tamarisk)

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Vegetative bunds not always protected
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Increasingly difficult to find acacia shrubs for
the traditional bunds
Haulage may take more than three days
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Construction of agims with bulldozer and gabions

• Replacement of upper section of the traditional
  agims with soil bunds and gabions
• Gabions at section where flood channel hits the
  diversion bund
• Flood protection on left bank to prevent further
  movement of Wadi Labka to the left

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Construction of agims with bulldozer and gabions
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Labor for gabion filling provided by farmers
without charge
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Wall of gabion baskets with earthen protection
Another layer of gabions will be added and the
earth bund will be increased
Use of geotextile will reduce wash out of fine
material at the bottom and prevent collapse
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Scope of work

• 1200 meter gabion works
• 120 days of bulldozer use
• Total costs USD 430,000
• Total cost/ ha USD 110

This may be compared with the cost of civil
engineering headworks (incl. breaching bund, link
canal and culvert, estimated at USD 7,000,000 (or
USD 1800/ha) for the same system
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River engineering versus civil engineering

• This river engineering approach taken is low
  cost
• It is also more appropriate than the civil
  engineering
• It follows the traditional system of diverting
  flood flows, based on splitting the flow in
  smaller proportions to make its management easier
• It follows the existing wate rights and does not
  interfere with it
• Very large floods will wash out part of the
  structures but will also ensure that the floods
  remains in the river bed and does not enter the
  command area, causing erosion

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