Exacerbation of levee failure with climate change: Insights from ERT monitoring

Adrian White, Paul Wilkinson, James Wookey, John-Michael Kendall, Ross Stirling, James Boyd, Arnaud Watlet, Anthony Blake , Joel Smethurst, Jonathan Chambers

Climate change in Western Europe is bringing hotter, drier summers and warmer, wetter winters. This will place greater stress on ageing levees by intensifying soil moisture fluctuations and increasing hydraulic loading. Conventional inspections cannot see inside these structures, so detecting and monitoring subsurface deterioration remains a critical challenge. We monitored a clay levee constructed from glacial till in northern England for four years using electrical resistivity tomography (ERT) at 48‑hour intervals, alongside environmental conditions and river level. Time‑lapse ERT shows resistivity variability concentrated in two zones: 1) The near‑surface active layer (upper ~1–1.5 m), which undergoes progressive summer drying followed by autumnal rewetting. 2) The foundation strata, where resistivity decreases with rising river levels, consistent with water movement beneath the levee. In the active layer, resistivity-derived drying depth correlates strongly with weather-derived soil moisture deficit (r = −0.95), quantitatively linking climatic forcing to seasonal drying. Applying this relationship to bias-corrected UKCP18 projections (RCP8.5) suggests average maximum drying depths could increase from ~0.6 m to >1.0 m by the late 21st century. These findings demonstrate that future levee design and risk-informed asset management must account for the combined impacts of increasing drought and flooding to ensure long-term structural resilience.