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Using eco-engineering to prevent against hazards in forests on landslide prone slopes

Using eco-engineering to prevent against hazards in forests on landslide prone slopes Alexia Stokes. What is eco-engineering?. Eco-engineering can be defined as the long-term ecological strategy to protect and/or restore a site with regard to natural or man-made hazards.

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Using eco-engineering to prevent against hazards in forests on landslide prone slopes

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  1. Using eco-engineering to prevent against hazards in forests on landslide prone slopes Alexia Stokes

  2. What is eco-engineering? Eco-engineering can be defined as the long-term ecological strategy to protect and/or restore a site with regard to natural or man-made hazards Usually on a large-scale…

  3. When can eco-engineering be used? Storms Erosion control Mass movement Source: S Mitchell UBC Storm-induced windthrow and landslide, Vancouver, Canada Source: M Ghestem, INRA Revegetating pasture lands, Inner Mongolia, China Slope restoration after landslide, Sichuan, China

  4. Railway Lhasa - Beijing Not to be (too) confused with ground bioengineering Vegetation combined with inert structures Usually on a small-scale…BUT… Live staking Source: Sotir, Chao Brushlayering

  5. Invented by… 156-87 BC Sao A sao was a mixture of stems and branches of willow and crushed rock tied together with twine or bamboo rope. It was recorded in Han Shu (by Ban Gu, 32-92 AD) that the great emperor of the Han Dynasty (Wu Di,) ordered his soldiers and generals to transport Saos to fix the breached levees of the Yellow River and stop the flood water. A section of the Sao-reinforced levee of the Han Dynasty was discovered in 2005 along the Bar River Needham Research Institute

  6. Evaluation of site Consideration of short-term risk to human safety and possibility of recurring hazard (storm, landslide, avalanche etc) High short-term risk to human safety and infrastructures. Recurring hazard is likely. Risk is low Use engineering methods to protect against immediate, potential dangers Is site to be restored/protected on a small- or large-scale? Determine costs over long-term (construction, planting, upkeep, management) and assess gain Site is small-scale. Expenses incurred equal gain Site is large-scale. Expenses incurred exceed gain Consider ground bio-engineering techniques Consider eco-engineering techniques When can eco-engineering be used?

  7. What is the best kind of vegetation to improve soil fixation on landslide prone slopes? Bamboo • 1) In plantation forest, does slope stability improve with tree age? • 2) On reforested slopes, does natural regeneration lead to instability in the early years? 9 years 30 years Bamboo Broadleaf saplings

  8. In plantation forest, does slope stability improve with tree age? In Sichuan, China: - We measured vegetation and soil variables for typical Cryptomeria japonica plantations of different ages Can then calculate slope stability safety factor (FOS) using slope stability model (<1.0 is unstable) 9 year old plantation = 2.0 (+27%) 20 year old plantation = 1.8 (+15%) 30 year old plantation = 1.5 (+17%) Genet M., Kokutse N., StokesA., FourcaudT., Cai X, Ji J, Mickovski S.B., 2008. Root reinforcement in plantations of Cryptomeria japonica D. Don: effect of tree age and stand structure on slope stability. Forest Ecology and Management. In press.

  9. On reforested slopes, does natural regeneration lead to instability in the early years? 3rd phase 2nd phase 1st phase Three phases of natural regeneration in Sichuan forests Bamboo only Bamboo and 5 year old deciduous mixed forest 20 year old deciduous mixed forest Phyllostachys nidularia (bamboo) Aralia elata Quercus infectoria Litsea cubeba Carya cathayensis Cynanchum stauntonii Betula laminifera Idesia polycarpa Cinnamomum wilsonii Notaphoebe cavalierei Phoebe nanmu Idesia polycarpa

  10. Height Width Angle Depth Exposure Vegetation An inventory of shallow landslides was made along one valley in the Sichuan Landslides often occur in bamboo forest because bamboo is a very shallow rooted pioneer 16 cm We then repeated the same procedure as before to determine the Factor of Safety at three different stages of forest succession 1st phase of succession = 1.0 ( +0%) – soil only 2nd phase of succession = 1.2 (+8%) 3rd phase of succession = 1.4 (+32%) 9 year old plantation = 2.0 (+27%) 20 year old plantation = 1.8 (+15%) 30 year old plantation = 1.5 (+17%) Genet M, Stokes A, Fourcaud T, Norris J 2008 The influence of plant diversity on slope stability in naturally regenerated sub-tropical montane forests at different phases of succession. Ecological Engineering. Submitted.

  11. Upslope Cohesion for one tree calculated from root system architecture Downslope New Research… Root cohesion mapping The position and density of trees will have an effect on small local landslips Danjon F., Barker D.H., Drexhage M., Stokes A. 2008. Using 3D plant root architecture in models of shallow slope stability. Annals of Botany, 101, 1281 – 1293.

  12. Mesh refinement of root-soil blocks integrating intra tree variation of root properties Root-soil blocks of individual trees Z D In a perfect (virtual) world…. NK Kokutse M. Jaeger Genet M., Kokutse N., StokesA., FourcaudT., Cai X, Ji J, Mickovski S.B., 2008. Root reinforcement in plantations of Cryptomeria japonica D. Don: effect of tree age and stand structure on slope stability. Forest Ecology and Management. In press.

  13. Slopes Decision Support System (SDSS) and Species Database A open source platform to implement Decision Support Systems (DSS) has been developed and published on the web. Can accept different models Species database currently being developed to help eco-engineers decide what to plant, how and where on a slope. Will be freely available on the web. Key to Function classification: AB – anchoring and buttressing of deep taproots; BC – bank and channel reinforcement; DR – deep reinforcement and soil strength enhancement; PH – phreatophytes removing soil moisture, SP – surface protection, shallow reinforcement and erosion control. Key to Efficacy of rockfall: 0 – species is not suitable for protection from rockfall; + – limited rockfall protection; ++ – good rockfall protection; +++ – excellent rockfall protection

  14. A Series of International Conferences on: Ground Bio- and Eco-engineering The Use of Vegetation to Improve Slope Stability Thessaloniki, Greece, September 2004 Beijing, China, July 2008 Vancouver, Canada, August 2012 In October 2008, a new International Network of Ground Bio- and Eco-engineers will be set up

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