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’.
The first intervention. Erosion control – the stabilization of slopes and river banks.
Bio-Engineering is the ‘soft’ alternative to traditional heavy civil-engineering. The latter uses concrete, gabions, rocks etc. The former doesn’t need systematic interventions of heavy machinery.
Bio- or Green Engineering groups and combines a wide range of techniques. The most common ones are :
- Revegetation through Hydromulching. This technique quickly establishes a vegetation cover. Therefore it immediately limits the superficial erosion caused by torrential rain, wind and run-off.
- Plantations create botanical diversity.
- Stolons and cuttings. New vegetation that grows from living plant material.
- Installation of ‘retaining combs’. These are installed in the erosion trench. They trap soil particles and sediments and in such prevent them from being washed away any further.
- Pre-vegetated rolls or blankets : these slow down the river current and moreover favour the sedimentation of (soil) particles.
- Revetments : you use these on riverbanks. And more specifically on those banks that are exposed to the strongest river currents. Revetments provide a solid and compact protection.
- Technique of ‘Bed of Saplings’ . This technique procures stability to the riverbank’s lower zone and in the meantime serves to dissipate the river current.
- Use of woven plant material or wattles that gives immediate protection to the lower part of the riverbank. Wattles form a real vegetal wall.
- Installation of fascines provides an immediate protection to the river bank. You use fascines mostly and specifically in river niches.
After a while the vegetation grows. It expands its green cover and develops a profound root zone. Ultimately, the big advantage is that it needs little or no maintenance.
The Second Intervention. Phyto-purification or Phyto-remediation.
The term Phyto-purification or purification using plants is rather general. It groups a number of ecological and traditional systems to purify ‘grey’ water. Such systems always use plants. Hence, there’s always a biological process active.
The most-used an most wide-spread system is this one : a filter populated with macrophytes (reeds, irises, phragmites, loosestrife, etc).
The third intervention. Phyto-stabilization.
Here we use special plant varieties. Because they reduce the mobility and the spread of contaminated soil elements. That way they reduce contamination caused by dust particles, through trace elements or even particles being washed away by water.
The root-hairs of these special plants limit the effects of the water and wind erosion. Even more, they prevent horizontal and vertical movement of toxic elements. Hence a unique technique which you equally can use as a temporary protection on contaminated soils.