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Imaging and monitoring tree‐induced subsidence using electrical resistivity imaging
- Source: Near Surface Geophysics, Volume 7, Issue 3, Feb 2009, p. 191 - 206
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- 01 Nov 2008
- 01 Apr 2009
- 01 Apr 2009
Abstract
Tree‐induced subsidence is a natural ground movement phenomenon that arises when tree roots absorb water from clay‐rich soils, causing them to shrink. Tree‐induced subsidence is particularly problematic for buildings and structures in close proximity to deciduous trees where changes in seasonal climate can have a significant effect on the degree of relative surface movement. Unfortunately, there is a lack of in‐depth understanding of tree‐induced subsidence dynamics and limited access to affordable/reliable assessment technologies for the victims of such phenomena. This paper presents and discusses the use of 2D electrical resistivity imaging (ERI) as a tool for recognizing tree‐related subsurface desiccation and its associated subsidence. The findings of a two year ERI study in a high‐risk tree‐induced subsidence environment are presented (mature Oak and Willow trees growing in expansive London Clays) where repeat (time‐lapse) resistivity profiles are compared to conventional ground levelling and soil moisture content data. This study confirms that ERI is a valuable tool for the characterization of seasonally varying subsurface moisture distributions and that the technique is capable of defining the architecture and temporal‐spatial variance of an active tree root system. Moreover, the method provides a critical insight into the visualization of tree‐induced subsidence phenomena and reveals promising practical potential for use as a modern, affordable, non‐invasive tree‐induced subsidence assessment tool.