Imaging seasonal moisture dynamics within a levee: two years of automated resistivity monitoring

White, A., Watlet, A., Boyd, J., Chambers, J., Smethurst, J., Stirling, R., Blake, A., Wilkinson, P., Harrison, H. and Meldrum, P. (2024) Imaging seasonal moisture dynamics within a levee: two years of automated resistivity monitoring. In 6th Asia Pacific Meeting on Near Surface Geoscience and Engineering. vol. 2024, European Association of Geoscientists and Engineers. 5 pp . (doi:10.3997/2214-4609.202471060).

Abstract

Levees (flood defences or dykes) play a crucial role in mitigating flood risks, and their long-term performance is linked to their surrounding environmental conditions and internal moisture dynamics. This study presents the results of a two-year automated resistivity monitoring program on a levee in Warden, Northumberland, England. The objective is to understand the seasonal moisture variations within the levee, with implications for its hydraulic conductivity, failure mechanisms and longer-term deterioration. The levee, constructed in 2007, was instrumented with a PRIME resistivity monitoring system, geotechnical sensors, and a weather station. The resulting 2D time-lapse resistivity model reveals three distinct regions: levee core, topsoil cover, and foundation strata, each exhibiting unique seasonal dynamics. The coefficient of variation analysis of the 2D resistivity data over the monitoring period identifies spatial patterns broadly correlating with the known material types. The near-surface zone shows particularly large seasonal moisture content cycles that may drive long-term deterioration. Temporal variability in the levee foundation caused by a fluctuating water table highlights the elevated hydraulic conductivity and the risk of seepage and piping through the foundation strata. This research contributes to our understanding of current seasonal dynamics to better determine the impacts of future climate change on levee performance.

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Contributors

Author: J. Smethurst

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