Optimizing Temperature Monitoring and Modeling for Evaluating Intervention Efficacy in River Levees

Abstract

The effective operation and monitoring of levees constitute pivotal factors in managing and safeguarding lowland territories during flood events and in regular flow conditions. Given their longitudinal structure and spatial soils heterogeneity, the monitoring of levee functionality poses complex challenges. This study investigates the application of a hybrid monitoring system combining traditional sensors and distributed temperature sensing (DTS) to assess seepage in a river levee in the northeast of Italy. The system, installed along three verticals at the levee toe, included pressure transducers and a DTS cable deployed using cone penetration test (CPT) equipment. The DTS system was deployed at the downstream toe of the levee on the landward side to detect temperature variations indicative of anomalous seepage within the levee body, assuming that water filtering through the levee exhibits a distinct temperature signature. To enable this installation method, a special disposable drill tip was developed and here discussed. Monitoring data collected over three years suggest seepage occurred primarily through shallow, permeable layers. This outcome guided the definition of the interventions aimed at mitigating local water seepage, providing insights both pre- and post-construction. Additionally, several finite element method (FEM) analyses of the instrumented levee section were carried out through a parametric study to assess the hydraulic and thermal conditions influencing thermal signal propagation within the levee, rather than to directly reproduce site-specific measurements, for a reliable use of DTS data to detect seepage. The study identified soil permeability as the dominant factor, with thermal properties and hydraulic gradient becoming significant only for low-permeability soils. The monitoring data guided an optimized intervention strategy, limiting sheet pile installation depth and reducing costs. Post-intervention monitoring validated the effectiveness of the intervention. This case study demonstrates the value of integrating advanced sensing technologies with traditional geotechnical practices and numerical modeling to enhance embankment safety assessment and guide targeted, cost-effective interventions.