This work is based on the assumption that a resistivity meter can effectively monitor water saturation in earth levees and can be used as a warning system when saturation exceeds the expected seasonal maxima. We performed time-lapse ERT measurements to assess the capability of this method to detect areas where seepage is critical. These measurements were also very useful to design a prototype monitoring system with remarkable savings by customizing the specifications according to field observations. The prototype consists of a remotely controlled low-power resistivity meter with a spread of 48 stainless steel 20 × 20 cm plate electrodes buried at half-meter depth. We deployed the newly-designed permanent monitoring system on a critical levee segment. A weather station and an ultrasonic water level sensor were also installed in order to analyse the correlation of resistivity with temperature, rainfalls and water level seasonal variations.The preliminary analysis of the monitoring data shows that the resistivity maps follow a very reasonable trend related with the saturation/drying cycle of the levee caused by the seasonal variations of the water level in the irrigation channel. Sharp water level changes cause delayed and smooth resistivity variations. Rainfalls and, to a lesser extent, temperature seem to have an influence on the collected data but effects are apparently negligible beyond 1 m depth. The system is currently operating and results are continuously monitored.

The aim of the Tech-Levee-Watch project is to combine geophysical technologies into an integrated system of diagnosis-monitoring-alert related to the vulnerability of earthen levees. A first milestone of the project consists in validating a fast scanning methodology based on a proper combination of portable geophysical instruments tailored to detect possible unstable areas of the levee structures. A second milestone consists in monitoring the most critical sites by installing a low-power fully-automatic geo-resistivity meter prototype programmed for wireless daily transmission of resistivity maps. The third milestone is the calibration of a relation between resistivity values and water content values so that resistivity maps will be transformed into water content maps used to feed a simulator of the levee stability. The final milestone consists of calibrating a set of thresholds in order to define an early-warning procedure to be delivered to administrations and citizens. This procedure can help authorities to organize maintenance of the embankments and to face critical situations that can lead to economic damages and loss of human lives.