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Bio- and Green Engineering

Bio- and Green Engineering or Habitat Creation are often defined as ‘a combination of techniques that use living material for 3 intervention types, with the final goal : a habitat that will be self-sustainable’.

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The first intervention is about erosion control and the stabilization of slopes and river banks.

Bio-Engineering is the ‘soft’ alternative – without the systematic intervention of heavy machinery – to traditional heavy civil-engineering (concrete, gabions, rocks, etc).

It groups and combines a wide range of techniques used in conjunction:

  • Revegetation through Hydromulching which establishes a vegetation cover that limits the superficial erosion caused by torrential rains and run-off
  • Plantations that allow to create botanical diversity
  • Stolons and cuttings that allow to grow a new shrub starting from living plant material
  • Installation of ‘retaining combs’ in the erosion trench, allowing to trap soil particles and sediments and prevent those from being further washed away
  • Pre-vegetated rolls or blankets that slow down the river current and favour the sedimentation of (soil) particles
  • Revetments that allow establishment of a compact and solid protection on riverbanks that are exposed to the strongest river currents
  • ‘Bed of Saplings’ that provides stability to the riverbank’s lower zone and serves to dissipate the river current
  • Use of woven plant material or wattles that give immediate protection to the lower part of the riverbank by forming a real vegetal wall
  • Installation of fascines that will provide an immediate protection to the river bank, is specifically used in water niches.

After a while, the vegetation grows, expands its green cover and root zone and only needs little or no maintenance.

The Second Intervention concerns Phyto-purification or Phyto-remediation

The terminology Phyto-purification (purification by use of plants) is a general one that groups various ecological and traditional systems to purify grey waters, always based on the use of plants during a biological process.
The system most often used and very widespread is where filters populated with macrophytes are being used (reeds, irises, phragmites, loosestrife, etc).

Schematic drawing of a horizontal flow filtration system making use of macrophyte plants.
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The third intervention is phyto-stabilization

In this specific case, special plant varieties are being used in order to reduce the mobility and spreading of contaminated soil elements. Be it under the form of dust, trace elements our particles being washed away by water or transported by wind.
The root-hairs of these plants will limit the effects of the hydraulic and wind erosion, as well as the horizontal and vertical movement of the toxic elements. This technique is also used as a temporary protection on contaminated soils.