Levee monitoring: DFOS Applications for understanding Levee Seepage

Enhancing the understanding of the geotechnical features of existing levees through on-site examination and monitoring is essential to estimate their security and that of the adjacent environment. However, these tasks are difficult due to the extensive length of the levees and the significant variability of soil texture within their structure and foundation, particularly in mountainous areas or/and when paleo rivers are present. Traditional methods for levee monitoring involve visual inspections, borehole drilling, in-situ tests, and the deployment of devices like piezometers and tensiometers. Regrettably, these methods often grapple with limitations imposed by their constrained spatial resolution. The investigation here presented tries to overcome the limits of traditional techniques, specifically probing the application of distributed fiber optical sensors (DFOS) for gauging temperature variations. Under normal conditions, temperature changes in the soil are mainly influenced by seasonal heat transfer from the air. However, during flooding events, notable temperature fluctuations both in space and time can revealing preferred flow paths, due to the presence of more permeable soils or large voids related to undergoing internal erosion. Two case studies are here presented, both aimed to the monitoring of a segment of Adige River's embankment in the province of Bolzano (Italy). The pilot tests differ for the DFOS installation configurations. Since the river encountered a significant flood event in Autumn 2023, the gathered data serve a dual purpose: advancing the comprehension of the hydraulic dynamics and the safety conditions of this segment of levee, but also appraising the reliability and potential of these cutting-edge monitoring methodologies.