Hydrological functioning of natural soil pipe networks and their impact on water transfer at the hillslope and small watershed scale are still little documented, in particular in the loess-derived soils of western Europe. This thesis aimed at providing a better understanding of the hydrological behavior of pipe networks at the hillslope scale at two sites in eastern and western Belgium using a variety of experimental and modeling techniques. This study demonstrated the potential of GPR for pipe network investigations. Results also revealed a complex threshold-like relationship between pipe discharge and rainfall, mainly controlled by seasonal differences in groundwater levels and to a lesser extent by antecedent precipitations. Natural soil pipes were shown to provide great hydrological connectivity between the upstream and downstream parts of the hillslope, a by-pass role that has important implications for runoff generation and solute transport. ; (AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 2019