Stability of flood embankments is strongly affected by the water flow taking place in the saturated and unsaturated soil. Monitoring of the water flow in flood embankments is therefore essential in the context of flood risk management to predict and prevent failures of embankments. Electrical Resistivity Tomography (ERT) is gaining popularity for its ability to monitor water regime in the subsoil more quickly, cost-effectively and on a larger scale compared to traditional geotechnical monitoring systems that rely on local sensors. This paper presents the application of ERT to the monitoring of water content in a flood embankment on the Adige River in Italy. The resistivity profiles obtained from the ERT measurements were converted into water content profiles via a laboratory-derived relationship between resistivity and water content. At the same time, local sensors to monitor pore water pressure were installed in the saturated and unsaturated zone of the embankment and this allowed reconstructing the water content regime in the embankment via inverse analysis of water flow. This offered the chance to benchmark ERT-derived water content against independent indirect measurements of water content in the field. ERT-inferred water content profiles based on laboratory calibration could capture the water content profiles derived from water flow analysis only qualitatively. This was attributed to artefacts in the ERT data inversion arising from the high contrasts in resistivity between different embankment layers. On the other hand, ERT proved to be a valuable tool to quantify the water content in the soil if field-specific relationship between water content and ERT measured resistivity is developed.
- electrical resistivity tomography
- water content monitoring
- flood embankment
- time domain reflectometry