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Division of Environment and Natural Resources

Measuring plant roots’ soil-reinforcement for streambank/slope stability

Active Last updated: 10.03.2023
End: dec 2023
Start: mar 2023
Status Active
Start - end date 01.03.2023 - 30.12.2023
Project manager Dominika Krzeminska
Division Division of Environment and Natural Resources
Department Soil and Land Use
Total budget 500 000
Funding source NIBIO FS-pilot

Issue: The mechanical effect of vegetation on streambank stability relates mainly to root reinforcement. Roots anchor themselves into the soil to support above-ground biomass, producing a reinforced soil matrix. The magnitude of root reinforcement mostly depends on root distribution and root mechanical properties, especially root tensile strengths. Roots property can be measured in the lab and in the field however, there are limited data on root-reinforced soil specimens and even less from Nordic countries (soil and vegetation type combination).

Main idea: Make a first step to fill the knowledge and data gap by exploring the opportunities of the laboratory infrastructure available at NIBIO - Triaxial Shear Strength Test. Adapt the procedures, sampling techniques and data processing in order to account for root reinforcement analysis.

Planned activities:

  • Start-up of laboratory equipment - Triaxial Shear Strength Test: upgrade the software, run test experiment.
  • Sampling the root-reinforced soil: select the sites to be sampled (out of existing/known experimental sites from other projects); collect representative root-reinforced soil samples; perform series of soil strength measurements both in the field (with Field Inspection Vane Tester).
  • Laboratory tests: series of Triaxial Shear Strength Tests accounting for both seasonal time scale and different vegetation type.
  • Modeling: include the findings as input in slope stability modeling (e.g., HYDRUS-2D, BSTEM)


Publications in the project


The hydrological processes associated with vegetation and their effect on slope stability are complex and so difficult to quantify, especially because of their transient effects (e.g. changes throughout the vegetation life cycle). Additionally, there is very limited amount of field based research focusing on investigation of coupled hydrological and mechanical influence of vegetation on stream bank behavior, accounting for both seasonal time scale and different vegetation types, and none dedicated to marine clay soils (typically soil type for Norway). In order to fill this gap we established hydrological and mechanical monitoring of selected test plots within a stream bank, covered with different types of vegetation, typical for Norwegian agricultural areas (grass, shrubs and trees). The soil moisture, groundwater level and stream water level were continuously monitored. Additionally, soil porosity and shear strength were measured regularly. Observed hydrological trends and differences between three plots (grass, tree and shrub) were analysed and formed the input base for stream bank stability modeling. We did not find particular differences between the grass and shrub plot but we did observe a significantly lower soil moisture content, lower soil porosity and higher shear strength within the tree plot. All three plots were stable during the monitoring period, however modeling scenarios made it possible to analyse potential differences in stream bank stability under different vegetation cover depending on root reinforcement and slope angle.