Strengths

  • Can be used on shores that drop off suddenly, where the bank has severely eroded or cannot be modified to create a gentle slope.
  • Rapid vegetation growth from the live cuttings, which slows water flow.
  • Can withstand relatively high current velocities and shear stresses.
  • Traps sediment and rebuilds the streambank.
  • Live woody vegetation provides habitat and aesthetic value.
  • A wide variety of geotextile products are available to match specific needs.
  • Effectiveness increases with time as vegetation becomes permanently established.

Limitation

  • A large amount of soil and rock must be available to fill the geotextiles.
  • Installation is complex and requires heavy machinery.
  • The cost is relatively high.
  • Can be labour intensive depending on the choice of geotextile material.
  • When placing live cuttings in the geotextile, plants must be installed during their dormant season in order for them to properly take root.

Vegetated geotextile

Application: Bridges, canals, coastlines, culverts and drains, dykes, embankments, floodgates, markets, roads and footpaths, stormwater outfall

Description: A vegetated geotextile consists of alternating layers of live branch cuttings and compacted soil with erosion control fabric (natural or synthetic geotextile) wrapped around each soil layer. The geotextile is secured by tucking it into the slope, keeping the soil in place. Live cuttings are placed between the geogrids, and a root structure is established to bind the soil within and behind the geogrids. The toe of the bank is stabilized by layers of rock on top of the soil layers. The live branch cuttings serve several practical purposes. They act as a buffer to reduce wave energy and shear stress at the face of the wall. In addition, having the branch cuttings present before the completion of the wall enables the vegetation to grow as rapidly as possible. Finally, once established the branches serve to bind the geogrids together and provide a root structure behind the wall, attaching it more securely to the shore.

Contribution to climate resilience: Vegetated geotextiles reduce erosion caused by rainfall as it covers and protects the soil surface and provides soil reinforcement through the vegetation roots. The velocity of run-off is slowed down and infiltration is increased. This increases the resilience of roadside slopes to extreme climatic events. Their effectiveness increases with time as the vegetation becomes fully established. Because they are constructed with local labour and materials, they require less energy to produce, are far more sustainable, and can often be applied in a quicker timeframe than traditional civil engineering works.

Supplementary sources of information:

http://www.ctre.iastate.edu/erosion/manuals/streambank/vegetated_geogrids.pdf

http://projects.geosyntec.com/npsmanual/Fact%20Sheets/Vegetated%20Geogrids.pdf

http://www.ctre.iastate.edu/erosion/manuals/streambank_erosion.pdf

http://dewprojects.countyofkane.org/dixieBriggsFromm/gallery.asp

This resilience-building measure is sourced from the Water Resource Adaptation Guide (2019) published by the National Council for Sustainable Development at the Ministry of Environment in Cambodia. The full Guide is available to download at URL https://ncsd.moe.gov.kh/sites/default/files/2019-10/Water%20Resources%20Adaptation%20Guide_March%202019_En.pdf