Assessing the ability of vegetation to reset hydraulic conditions in a capillary barrier
Assessing the ability of vegetation to reset hydraulic conditions in a capillary barrier
A capillary barrier system (CBS) can help to regulate water fluctuations within the built environment and stabilise slopes that are vulnerable to rainfall-induced failures, such as those formed from high-plasticity clays. The barrier prevents water percolation into the underlying slope as a result of the unsaturated characteristics of the fine and coarse layers of the CBS. It also provides water storage, minimising run-off and acting as an effective element of a sustainable (urban) drainage system (SuDS). This paper will explore the effect of adding vegetation to improve the performance of such a system. The results of 1:1 full-scale physical models of a unit-cell within a vegetated CBS are presented to evaluate the ability of live vegetation to remove water from the barrier by evapotranspiration (ET) following saturation (e.g. from an extreme rainfall event), re-setting the beneficial hydraulic characteristics of the barrier and increasing resilience to subsequent events. The physical models are subsequently subjected to re-wetting after ET, to determine how quickly the positive engineering characteristics are regained. In conjunction with changes to fundamental physical characteristics induced by the vegetation (from element tests), including permeability and water storage capacity, the model testing demonstrates the potential for using live vegetation to create a nature-enhanced CBS that has significantly improved performance for the small cost of ongoing vegetation management.
David Boldrin; Jonathan A. Knappett; A. K. Leung; Glyn Bengough
11th International Conference on Physical Modelling in Geotechnics (ICPMG2026)
Special Session 8: Nature-based solution for sustainable geotechnical systems
https://doi.org/10.53243/ICPMG2026-219